[Gasification] colortune plugs

[jamast]

> Getting the Air/fuel ratio correct is also vital.  Using a
> "colortune" sparkplug is the best way to really know when you have
> the correct mixture as you can see the flame color within the
> combustion chamber.

..hum.  That assumes we know right shade of blue (or green or
violet?).  And at least I don't. ;o)  Has anyone played with
colortune spark plugs and on wood gas?

..........i have used various transparent plugs for years, but of late, 
computers do the job better, between a cheap gas analyser and a laser 
thermometer you can pretty well pinpoint any problem quickly..   for 
multiple cylinders colortune plugs might be helpful in finding obstructions, 
very rare though.. the common use would of course be mixture control and 
you're right, the color can be tricky to get just so..
i've used a lambda with a built in heater, great for gasoline but it was 
confused by wood gas, i'll try it again and post
robert saint amour

----- Original Message ----- 
From: <gasification-request at lists.bioenergylists.org>
To: <gasification at lists.bioenergylists.org>
Sent: Friday, February 25, 2011 12:00 PM
Subject: Gasification Digest, Vol 6, Issue 23


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> Today's Topics:
>
>   1. Re: Emissions fines (linvent at aol.com)
>   2. Re: ideal wood gas engine (Arnt Karlsen)
>   3. Re: ideal wood gas engine (doug.williams)
>   4. Re: ideal wood gas engine (GF)
>   5. Re: ideal wood gas engine (GF)
>   6. Re: ideal wood gas engine (Bill Klein)
>   7. Re: ideal wood gas engine (dave)
>   8. NZ Earthquake, OT (doug.williams)
>   9. Re: ideal wood gas engine (Luke Gardner)
>  10. Re: ideal wood gas engine (Daniel Chisholm)
>  11. Re: ideal wood gas engine (Bob Stuart)
>  12. Re: NZ Earthquake, OT (bayent at ns.sympatico.ca)
>  13. Re: ideal wood gas engine (Thomas Reed)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 24 Feb 2011 15:21:56 -0500 (EST)
> From: linvent at aol.com
> To: gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] Emissions fines
> Message-ID: <8CDA2779AD060B5-1FF0-7128 at webmail-m085.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> Dear Tom,
>      The original statement which started this thread was that
> gasifiers got violations, now as I initially asked, the installations
> were not gasifiers. If the industry is going to keep it's black eyes to
> a minimum, it needs to deal with misnomers and the like.
>      Adding oxidizer over the bed also occurs in combustors. It reduces
> the gas heating value by combusting some of the fixed gases which react
> more rapidly than the aerosols or tars, and the reduced heating value
> of the gas causes problems in operating engines as the PRM system did
> in Sorrento, Italy on olive pits. There are better ways of dealing with
> the tars which increase the heating value of the gas while cleaning it
> adequately to operate IC engine, be transported distances and the like.
>      The three vessel unit which takes virtually any combustible
> feedstock and converts it into a clean, cool gas suitable for engine
> operation demonstrates this. A char residue from a cellulosic chemical
> plant with 33% ash,  5500 btu/lb. at 20% moisture was run at what
> appears to be around 40% moisture and the gas had 24-27% hydrogen in
> it. The nitrogen also appears to be much less than normal air fired
> gasification content. Adjustment of operating temperature changes the
> hydrogen content.
> Sincerely,
> Leland T. "Tom" Taylor
> President
> Thermogenics Inc.
>
> -----Original Message-----
> From: Tom Miles <tmiles at trmiles.com>
> To: 'Discussion of biomass pyrolysis and gasification'
> <gasification at lists.bioenergylists.org>
> Sent: Mon, Feb 21, 2011 7:34 pm
> Subject: Re: [Gasification] Emissions fines
>
> Tom,
>
> Don't get Kevin started on definitions of gasification. :-)
>
> Try http://en.wikipedia.org/wiki/Gasification
>
> The plants that received fines do not have gasifiers. The only
> similarity is that they convert wet wood to steam. They use fluidized
> bed combustors. They use excess air directly in the fluidized bed of
> sand. They also burn fuels such as urban wood waste that require acid
> gas control. An FB combustor allows you to control acid gas directly by
> adding limestone to the bed to form calcium sulfate or calcium chloride
> that is removed as a particulate. In a combustor the heat transfer -
> boiler and convective sections - are integral to the furnace-boiler
> design. In the Nexterra and other gasifier application the gas is
> transported from the gasifier to a burner that is in a separate boiler
> enclosure. (From 1985-1998 Interpretations of the tax code allowed the
> grate portion of a furnace to be called a gasifier when operated with
> limited air such that staged combustion within a boiler qualified for a
> producer gas tax credit. That credit has now expired.)
>
> It's important to look at the whole system. Nexterra uses a unique
> proprietary bed design, a low velocity above the bed that reduces
> particulate, a partial oxidation step to clean up tars between the
> gasifier and the burner in the boiler. Tar reduction is similar in
> concept to what other fixed bed suppliers, like PRM and PrimEnergy,
> have done for years. Combustible gas is transported from the gasifier
> to a burner in the boiler. The gas fired in the boiler is clean enough
> to use the ESP for particulate control. The combination of the low NOx
> precursors from the gasifier and their burner design allows them good
> CO and NOx control. Comparative data are in the Levelton report.
>
> Tom Miles
>
>
> -----Original Message-----
> From: gasification-bounces at lists.bioenergylists.org
> [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of
> linvent at aol.com
> Sent: Monday, February 21, 2011 4:05 PM
> To: gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] Emissions fines
>
> Dear Tom,
>      In comparing the Kruger Products installation to the ones which
> received fines, one might be tempted to say that a fixed bed is better
> than a fluidized bed, but one would have to compare emission standards
> between the two jurisdictions to firmly make this claim. The Nexterra
> design has a relatively high tar yield.
>       The word gasification in my opinion is still misapplied unless
> the
> gas can be cleaned and transported across a jurisdictional boundary for
> use, otherwise, it is still a dual stage combustor.
> Sincerely,
> Leland T. "Tom" Taylor
> President
> Thermogenics Inc.
> www.thermogenics.com
> 505-463-8422
>
> -----Original Message-----
> From: Tom Miles <tmiles at trmiles.com>
> To: 'Discussion of biomass pyrolysis and gasification'
> <gasification at lists.bioenergylists.org>
> Sent: Sun, Feb 20, 2011 8:24 pm
> Subject: Re: [Gasification] Emissions fines
>
> Pulp and Paper Canada (Feb 2011) reporting on a gasifier-boiler
> application:
> http://www.pulpandpapercanada.com/issues/story.aspx?aid=1000402062
> Kruger's Biomass Gasifier Fuels Customers' Need for GreenBiomass
> gasification has quantifiable environmental benefits to show customers:
> fewer GHG emissions, less fossil fuel, better air quality.By: By Tony
> Kryzanowski
>
>
>
> _______________________________________________
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>
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 24 Feb 2011 22:20:29 +0100
> From: Arnt Karlsen <arnt at c2i.net>
> To: gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <20110224222029.77180740 at celsius.local>
> Content-Type: text/plain; charset=US-ASCII
>
> On Mon, 21 Feb 2011 15:47:46 +1300, Tony.Batchelor wrote in message
> <AFDAE51957292F4A822CE0CC3DFBE998018E6B5F48B0 at TCSEXCCR.correspondence.school.nz>:
>
>> Getting the Air/fuel ratio correct is also vital.  Using a
>> "colortune" sparkplug is the best way to really know when you have
>> the correct mixture as you can see the flame color within the
>> combustion chamber.
>
> ..hum.  That assumes we know right shade of blue (or green or
> violet?).  And at least I don't. ;o)  Has anyone played with
> colortune spark plugs and wide-band lambda sensors on wood gas?
>
> -- 
> ..med vennlig hilsen = with Kind Regards from Arnt Karlsen
> ...with a number of polar bear hunters in his ancestry...
>  Scenarios always come in sets of three:
>  best case, worst case, and just in case.
>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 25 Feb 2011 13:46:50 +1300
> From: "doug.williams" <Doug.Williams at orcon.net.nz>
> To: "Discussion of biomass pyrolysis and gasification"
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <F82C7B1869BF47399FF88B43847F6C8F at dougspc>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Tony and Colleagues
>
>> This may be my first post to this site, I trust you will all not hope it 
>> is my last.
>
> As a fellow New Zealander, lets hear more from you, we cover a lot of 
> engine "stuff", and new voices are most welcome.
>
>> Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
>> sparkplug is the best way to really know when you have the correct 
>> mixture as you can see the flame color within the combustion chamber.
>
> Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it to teach 
> how exhaust temperatures and engine sound changed across gas/air mixtures, 
> using a single cylinder Iron Horse engine. I sent both Kevin and Arnt a 
> copy of the colour guide out of our kit, seeing as they were interested in 
> this subject.
>
>> A turbocharger can be used to increase the volume of mixture which is 
>> drawn into engine but whether or not they are practical given the 
>> possibility of contaminated gas is something I cannot comment on.
>
> This is a problem for producer gas in most DIY systems. We do better at 
> the commercial level with more sophisticated filtration systems, but it is 
> better to use naturally aspirated engines of larger cylinder capacity of 
> lower RPM, than undersized turbocharged engines relying on high RPM for 
> DIY projects.
>
>> The Mean effective pressure within the engine during the combustion 
>> stroke, is largely dependent on the length of stroke of the engine, the 
>> compression ratio and the ignition timing.
>> The stroke cannot easily be altered but the compression ratio can be 
>> changed on some engines by machining the cylinder head.
>
> Generally speaking, this would mainly be applied to very old engines, 
> probably pre-dating around 1949. The literature records a lot of work in 
> this area of compression ratios by Woods in the late 1930's early 40's 
> (from memory), where it was established that around 11:1 was the optimum 
> for producer gas. At this point, the extra friction from compressive 
> forces consumed the "extra energy", and little was gained from higher 
> compression.
>
>> If a petrol (spark ignited) engine is run on wood gas or any other gas, 
>> the Ignition timing has to be altered.  In general the ignition timing 
>> will be advanced by several degrees, in order to ensure as high a mean 
>> pressure as possible is reached during the combustion stroke.
>
> This is true, but remember that WW2 petrol was of lower octane, and 
> required ignition advancement. Modern engines have that advancement 
> already built in for the higher octane available today. Then, separate 
> charcoal gasifiers away from wood gasifiers, because the H2 content again 
> changes ignition behaviour. Most engines set up to operate on LPG or 
> natural gas, are from 10-12:1 compression ratio (of the smaller sizes), 
> and run without alteration on 110-120 octane producer gas perfectly. 
> Having said that, you can always tweak them if the situation demands that 
> degree of perfection. The engine is the least of your worries if the gas 
> making is unstable (:-)
>
>> The benefit of using a computer controlled ignition system is that most 
>> if not all computer controlled systems have a "knock" sensor.  The 
>> purpose of this device is to sense when the ignition of the fuel has 
>> caused the pressure within the cylinder to rise so high that the 
>> remaining un burnt fuel spontaneously explodes.  This results in engine 
>> knock, the resulting noise is commonly known as "pinking"   Diesel 
>> engines knock a lot of the time because the very design of the engine is 
>> to raise the fuel temperature to point when it spontaneously burns.
>
> Speaking "generally", producer gas has no problem in most standard spark 
> ignition engines, as the spontaneous ignition temperature for producer gas 
> in our experience, is around 600C. You find these compression temperatures 
> in diesels around 16:1 ratio, and again from experience, once you go over 
> 17:1, the spontaneous ignition temperature makes the engine very unstable. 
> We worked with Lister (NZ)  to develop dual fuel conversion kits for the 
> Pacific region, converted to gas Ford diesels in the UK, Ford natural gas 
> engines in USA, and purpose built gas engines in Germany.
>
> In all cases, the operating temperatures around the engine can affect the 
> behaviour of the ignition temperatures, as will the actual CO,H2, and CH4 
> content. Any uncracked hydrocarbons will also affect the timing behaviour, 
> so be careful how you tinker with the timing. Nothing is written in stone!
>
>> Older engines that use a Distributor lack the anti-knock feature. 
>> Commonly distributors have a simple mechanical advise mechanism, to 
>> advance the ignition as the engine revs faster, and a >Vacuum Retard 
>> mechanism which aids acceleration.  Engines which are subject to varying 
>> loads, can benefit from the retard mechanism if there is any kind of 
>> control valve /butterfly on the >intake, which would alter the manifold 
>> vacuum.
>
> My genset engine is a  1949 Hillman engine, one of the early higher 
> compression engines  (8:1) out of the UK. The vacuum advance and retard is 
> disconnected, but we have not noticed any problems across a wide range of 
> outputs for 1,000's of hours. It is a moot point however, and I will 
> reconnect it next time I play to see if it makes any difference.
>>
>> Anyone setting the timing on an engine with a fixed load-speed, needs to 
>> be sure the advance/retard mechanisms are either working correctly or 
>> have been locked up. As fixed speed engines can "hunt" if there is any 
>> faults in or if there is any small changes in the loading or fuel supply.
>
> Gensets have to operate at fixed speed, so use a governor on the throttle 
> butterfly, and as I said, our advance/retard control is disconnected, so 
> cannot in any way affect how the engine hunts on load or gas changes. 
> Producer gas has many surprises as an engine fuel, and we learn more by 
> the day.
>
> Most of the above comments apply to fixed speed (RPM) applications used 
> for electrical power generation, both base and variable loads, from our 
> installation experiences 1978- 2010.
>
> Doug Williams,
> Fluidyne Gasification.
>
>
>
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> ------------------------------
>
> Message: 4
> Date: Thu, 24 Feb 2011 19:51:33 -0500
> From: GF <gfwhell at aol.com>
> To: gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <8CDA29D4878D464-1CC4-3D40 at webmail-m087.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Back when Teddy was at Odds with Arthur. Teddy imposed the three day week. 
> I told my Boss that I could put ourselves back to a six day week with the 
> aid of a Generator which we just "happened to have" for testing machines 
> for export, This electric motor driven contraption was set up to produce 
> 60 htz 3ph and needed to be "modified" to produce 50 htz. to run on NG. We 
> needed about 20 HP  for our requirements, So I got hold of a scrap Morris 
> Minor Engine, and swapped it out with the electric motor,which was belt 
> coupled to the Generator.
> Some changes in the taper lock pulleys and belts set the new contraption 
> up for the lower frequency. Because the engine was "small" I decided to 
> run it at a speed  fitting it's optimum out put curve. There were other 
> problems such as the field voltage control of the generator  and the speed 
> regulation to match the ever changing load of our small manufacturing 
> plant. I envisaged the "Power Police" pouncing, armed with electrical 
> measuring devices to make sure we were obeying the emergency directives. 
> I designed a simple throttle control comprising of two identical 
> synchronous motors, facing each other. where if they both ran at the same 
> speed. the output leaver would remain stationary. one of the motors was 
> powered by a battery powered "Shaving" inverter giving a steady 50 hrtz 
> while the other clock motor was connected to one of the phases of the 
> generator. It did work but due to the heavy fluctuating loads the out put 
> was like a roller coaster.
> I finally cheated, by putting three lamps between the grid supply and the 
> generator and when they were all "out" I threw the main breaker and we 
> were co-generating. A highly frowned upon practice due to the possibility 
> of electrocuting unsuspecting grid lineman. In this case how ever. our 
> small power plant could not have remained on line for more than a second 
> if the grid had failed.
> The grid stabilized our generator, I opened it up to full throttle and 
> watched the Meter running backwards, which it did most of the time except 
> when our large mill was in "start" mode. I am glad we did not have a visit 
> from the power police.
>
> GF
>
>
>
>
>
>
> -----Original Message-----
> From: Tony.Batchelor <Tony.Batchelor at tekura.school.nz>
> To: 'Discussion of biomass pyrolysis and gasification' 
> <gasification at lists.bioenergylists.org>
> Sent: Sun, Feb 20, 2011 9:47 pm
> Subject: Re: [Gasification] ideal wood gas engine
>
>
>
> Dear Kelvin and members.
> This may be my first post to this site, I trust you will all not hope it 
> is my
> ast.
> Engine power output is a complex issue,  factors such as the energy 
> density of
> he fuel, the air/fuel ratio that enters the engine, the volume of air/fuel
> hich is able to enter the engine during the induction stroke, and the
> ompression pressure reached prior to ignition and the mean pressure 
> reached
> uring the combustion stroke are just some of the most important factors.
> esides the detailed design of intake manifold and exhaust pipes which 
> influence
> ow well an engine can breathe.
> Where an engine is to be run on wood gas alone, it would be better to do 
> away
> ith as many obstructions in the intake manifolds as possible.  The key 
> point
> eing to get as much of the gas/air mixture into the engine. This is one 
> reason
> hy Diesel engines are good as they only have suck in air, as fuel is added
> nternally.  Fuel injected petrol engines come close behind, carburetor 
> models
> re generally more restricted as air passes through the carburetor.
> Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
> sparkplug
> s the best way to really know when you have the correct mixture as you can 
> see
> he flame color within the combustion chamber.
> A turbocharger can be used to increase the volume of mixture which is 
> drawn into
> ngine but whether or not they are practical given the possibility of
> ontaminated gas is something I cannot comment on.
> The Mean effective pressure within the engine during the combustion 
> stroke, is
> argely dependent on the length of stroke of the engine, the compression 
> ratio
> nd the ignition timing.
> he stroke cannot easily be altered but the compression ratio can be 
> changed on
> ome engines by machining the cylinder head.
> ltering the intake air pressure, using a turbo or other methods. Such as
> ooling the intake air/fuel temperature.
> nd by changing the ignition timing.
> f a petrol (spark ignited) engine is run on wood gas or any other gas, the
> gnition timing has to be altered.  In general the ignition timing will be
> dvanced by several degrees, in order to ensure as high a mean pressure as
> ossible is reached during the combustion stroke.
> he benefit of using a computer controlled ignition system is that most if 
> not
> ll computer controlled systems have a "knock" sensor.  The purpose of this
> evice is to sense when the ignition of the fuel has caused the pressure 
> within
> he cylinder to rise so high that the remaining un burnt fuel spontaneously
> xplodes.  This results in engine knock, the resulting noise is commonly 
> known
> s "pinking"   Diesel engines knock a lot of the time because the very 
> design of
> he engine is to raise the fuel temperature to point when it spontaneously
> urns.
> lder engines that use a Distributor lack the anti-knock feature. Commonly
> istributors have a simple mechanical advise mechanism, to advance the 
> ignition
> s the engine revs faster, and a Vacuum Retard mechanism which aids
> cceleration.  Engines which are subject to varying loads, can benefit from 
> the
> etard mechanism if there is any kind of control valve /butterfly on the 
> intake,
> hich would alter the manifold vacuum.
> Anyone setting the timing on an engine with a fixed load-speed, needs to 
> be sure
> he advance/retard mechanisms are either working correctly or have been 
> locked
> p. As fixed speed engines can "hunt" if there is any faults in or if there 
> is
> ny small changes in the loading or fuel supply.
> Tony Batchelor, ex, road transport engineer, now teaching physics. 
> Wellington,
> ew Zealand.
>
>
> -----Original Message-----
> rom: gasification-bounces at lists.bioenergylists.org 
> [mailto:gasification-bounces at lists.bioenergylists.org]
> n Behalf Of Kevin
> ent: Monday, 21 February 2011 1:06 p.m.
> o: Discussion of biomass pyrolysis and gasification
> ubject: Re: [Gasification] ideal wood gas engine
> Dear Charles
> Your stated need is for "about 20 HP" at 1,800 RPM
> You should be able to get about 21.4 HP with an engine of 2500 CC (153 
> Cubic
> nches), burning about 19 kG/Hr (42 Lbs/Hr)
> It would be very helpful if others could comment on the other aspects of 
> an
> ngine.... in particular, the Ignition system, whether Distributor or
> Computer Controlled", and the implications of using a Fuel Injected 
> engine,
> ather than a carburetor engine.
> Best wishes,
> Kevin
> ----- Original Message -----
> rom: <bayent at ns.sympatico.ca>
> o: <gasification at lists.bioenergylists.org>
> ent: Sunday, February 20, 2011 11:32 AM
> ubject: [Gasification] ideal wood gas engine
>
>
> Content analysis details:   (0.0 points)
>
>  pts rule name              description
> ---- ---------------------- --------------------------------------------------
> _SUMMARY_
>
> Hi All,
>
> I have several engines to chose from here for my next wood gas project.
> Going to go ahead with it and just hope the stink has settled form my
> insurance company ripping hair out of their heads. ( hope they are not on
> here.. bugger )
> Besides this is not a heating device so should not count.
> What out of the junk yard specials would be considered ideal for wood gas
> give I Only need this time to come up with 20 hp at 1,800 rpm?
> I have everything in the shop for a Mike clone.
> Spending a few bucks for the right engine is going to be real cheep just
> now.
> I am not keen on stuck valves through pistons. ( it that ever happens...
> never mind )
>
> Regards all,
> Charles
>
> _______________________________________________
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> ------------------------------
>
> Message: 5
> Date: Thu, 24 Feb 2011 20:04:01 -0500
> From: GF <gfwhell at aol.com>
> To: Doug.Williams at orcon.net.nz, gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <8CDA29F0655420B-1CC4-3F7D at webmail-m087.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Doug,
> Has there ever been observation of increased "oxygen" when using wood gas, 
> I have seen these electrolizer cracking units which apparently enhance 
> performance
> of ICE's, there may not be any great economy here but cleaner burning may 
> be apparent together with enhanced hydrogen intake?
>
> GF
>
>
>
>
> -----Original Message-----
> From: doug.williams <Doug.Williams at orcon.net.nz>
> To: Discussion of biomass pyrolysis and gasification 
> <gasification at lists.bioenergylists.org>
> Sent: Thu, Feb 24, 2011 7:46 pm
> Subject: Re: [Gasification] ideal wood gas engine
>
>
> Hi Tony and Colleagues
>
>> This may be my first post to this site, I trust you will all not hope it 
>> is my last.
>
> As a fellow New Zealander, lets hear more from you, we cover a lot of 
> engine "stuff", and new voices are most welcome.
>
>> Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
>> sparkplug is the best way to really know when you have the correct 
>> mixture as you can see the flame color within the combustion chamber.
>
> Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it to teach 
> how exhaust temperatures and engine sound changed across gas/air mixtures, 
> using a single cylinder Iron Horse engine. I sent both Kevin and Arnt a 
> copy of the colour guide out of our kit, seeing as they were interested in 
> this subject.
>
>> A turbocharger can be used to increase the volume of mixture which is 
>> drawn into engine but whether or not they are practical given the 
>> possibility of contaminated gas is something I cannot comment on.
>
> This is a problem for producer gas in most DIY systems. We do better at 
> the commercial level with more sophisticated filtration systems, but it is 
> better to use naturally aspirated engines of larger cylinder capacity of 
> lower RPM, than undersized turbocharged engines relying on high RPM for 
> DIY projects.
>
>> The Mean effective pressure within the engine during the combustion 
>> stroke, is largely dependent on the length of stroke of the engine, the 
>> compression ratio and the ignition timing.
>> The stroke cannot easily be altered but the compression ratio can be 
>> changed on some engines by machining the cylinder head.
>
> Generally speaking, this would mainly be applied to very old engines, 
> probably pre-dating around 1949. The literature records a lot of work in 
> this area of compression ratios by Woods in the late 1930's early 40's 
> (from memory), where it was established that around 11:1 was the optimum 
> for producer gas. At this point, the extra friction from compressive 
> forces consumed the "extra energy", and little was gained from higher 
> compression.
>
>> If a petrol (spark ignited) engine is run on wood gas or any other gas, 
>> the Ignition timing has to be altered.  In general the ignition timing 
>> will be advanced by several degrees, in order to ensure as high a mean 
>> pressure as possible is reached during the combustion stroke.
>
> This is true, but remember that WW2 petrol was of lower octane, and 
> required ignition advancement. Modern engines have that advancement 
> already built in for the higher octane available today. Then, separate 
> charcoal gasifiers away from wood gasifiers, because the H2 content again 
> changes ignition behaviour. Most engines set up to operate on LPG or 
> natural gas, are from 10-12:1 compression ratio (of the smaller sizes), 
> and run without alteration on 110-120 octane producer gas perfectly. 
> Having said that, you can always tweak them if the situation demands that 
> degree of perfection. The engine is the least of your worries if the gas 
> making is unstable (:-)
>
>> The benefit of using a computer controlled ignition system is that most 
>> if not all computer controlled systems have a "knock" sensor.  The 
>> purpose of this device is to sense when the ignition of the fuel has 
>> caused the pressure within the cylinder to rise so high that the 
>> remaining un burnt fuel spontaneously explodes.  This results in engine 
>> knock, the resulting noise is commonly known as "pinking"   Diesel 
>> engines knock a lot of the time because the very design of the engine is 
>> to raise the fuel temperature to point when it spontaneously burns.
>
> Speaking "generally", producer gas has no problem in most standard spark 
> ignition engines, as the spontaneous ignition temperature for producer gas 
> in our experience, is around 600C. You find these compression temperatures 
> in diesels around 16:1 ratio, and again from experience, once you go over 
> 17:1, the spontaneous ignition temperature makes the engine very unstable. 
> We worked with Lister (NZ)  to develop dual fuel conversion kits for the 
> Pacific region, converted to gas Ford diesels in the UK, Ford natural gas 
> engines in USA, and purpose built gas engines in Germany.
>
> In all cases, the operating temperatures around the engine can affect the 
> behaviour of the ignition temperatures, as will the actual CO,H2, and CH4 
> content. Any uncracked hydrocarbons will also affect the timing behaviour, 
> so be careful how you tinker with the timing. Nothing is written in stone!
>
>> Older engines that use a Distributor lack the anti-knock feature. 
>> Commonly distributors have a simple mechanical advise mechanism, to 
>> advance the ignition as the engine revs faster, and a >Vacuum Retard 
>> mechanism which aids acceleration.  Engines which are subject to varying 
>> loads, can benefit from the retard mechanism if there is any kind of 
>> control valve /butterfly on the >intake, which would alter the manifold 
>> vacuum.
>
> My genset engine is a  1949 Hillman engine, one of the early higher 
> compression engines  (8:1) out of the UK. The vacuum advance and retard is 
> disconnected, but we have not noticed any problems across a wide range of 
> outputs for 1,000's of hours. It is a moot point however, and I will 
> reconnect it next time I play to see if it makes any difference.
>>
>> Anyone setting the timing on an engine with a fixed load-speed, needs to 
>> be sure the advance/retard mechanisms are either working correctly or 
>> have been locked up. As fixed speed engines can "hunt" if there is any 
>> faults in or if there is any small changes in the loading or fuel supply.
>
> Gensets have to operate at fixed speed, so use a governor on the throttle 
> butterfly, and as I said, our advance/retard control is disconnected, so 
> cannot in any way affect how the engine hunts on load or gas changes. 
> Producer gas has many surprises as an engine fuel, and we learn more by 
> the day.
>
> Most of the above comments apply to fixed speed (RPM) applications used 
> for electrical power generation, both base and variable loads, from our 
> installation experiences 1978- 2010.
>
> Doug Williams,
> Fluidyne Gasification.
>
>
>
>
>
>
>> Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
>> sparkplug is the best way to really know when you have the correct 
>> mixture as you can see the flame color within the combustion chamber.
>
> Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it to teach 
> how exhaust temperatures and engine sound changed across gas/air mixtures, 
> using a single cylinder Iron Horse engine. I sent both Kevin and Arnt a 
> copy of the colour guide out of our kit, seeing as they were interested in 
> this subject.
>
>> A turbocharger can be used to increase the volume of mixture which is 
>> drawn into engine but whether or not they are practical given the 
>> possibility of contaminated gas is something I cannot comment on.
>
> This is a problem for producer gas in most DIY systems. We do better at 
> the commercial level with more sophisticated filtration systems, but it is 
> better to use naturally aspirated engines of larger cylinder capacity of 
> lower RPM, than undersized turbocharged engines relying on high RPM for 
> DIY projects.
>
>> The Mean effective pressure within the engine during the combustion 
>> stroke, is largely dependent on the length of stroke of the engine, the 
>> compression ratio and the ignition timing.
>> The stroke cannot easily be altered but the compression ratio can be 
>> changed on some engines by machining the cylinder head.
>
> Generally speaking, this would mainly be applied to very old engines, 
> probably pre-dating around 1949. The literature records a lot of work in 
> this area of compression ratios by Woods in the late 1930's early 40's 
> (from memory), where it was established that around 11:1 was the optimum 
> for producer gas. At this point, the extra friction from compressive 
> forces consumed the "extra energy", and little was gained from higher 
> compression.
>
>> If a petrol (spark ignited) engine is run on wood gas or any other gas, 
>> the Ignition timing has to be altered.  In general the ignition timing 
>> will be advanced by several degrees, in order to ensure as high a mean 
>> pressure as possible is reached during the combustion stroke.
>
> This is true, but remember that WW2 petrol was of lower octane, and 
> required ignition advancement. Modern engines have that advancement 
> already built in for the higher octane available today. Then, separate 
> charcoal gasifiers away from wood gasifiers, because the H2 content again 
> changes ignition behaviour. Most engines set up to operate on LPG or 
> natural gas, are from 10-12:1 compression ratio (of the smaller sizes), 
> and run without alteration on 110-120 octane producer gas perfectly. 
> Having said that, you can always tweak them if the situation demands that 
> degree of perfection. The engine is the least of your worries if the gas 
> making is unstable (:-)
>
>> The benefit of using a computer controlled ignition system is that most 
>> if not all computer controlled systems have a "knock" sensor.  The 
>> purpose of this device is to sense when the ignition of the fuel has 
>> caused the pressure within the cylinder to rise so high that the 
>> remaining un burnt fuel spontaneously explodes.  This results in engine 
>> knock, the resulting noise is commonly known as "pinking"   Diesel 
>> engines knock a lot of the time because the very design of the engine is 
>> to raise the fuel temperature to point when it spontaneously burns.
>
> Speaking "generally", producer gas has no problem in most standard spark 
> ignition engines, as the spontaneous ignition temperature for producer gas 
> in our experience, is around 600C. You find these compression temperatures 
> in diesels around 16:1 ratio, and again from experience, once you go over 
> 17:1, the spontaneous ignition temperature makes the engine very unstable. 
> We worked with Lister (NZ)  to develop dual fuel conversion kits for the 
> Pacific region, converted to gas Ford diesels in the UK, Ford natural gas 
> engines in USA, and purpose built gas engines in Germany.
>
> In all cases, the operating temperatures around the engine can affect the 
> behaviour of the ignition temperatures, as will the actual CO,H2, and CH4 
> content. Any uncracked hydrocarbons will also affect the timing behaviour, 
> so be careful how you tinker with the timing. Nothing is written in stone!
>
>> Older engines that use a Distributor lack the anti-knock feature. 
>> Commonly distributors have a simple mechanical advise mechanism, to 
>> advance the ignition as the engine revs faster, and a >Vacuum Retard 
>> mechanism which aids acceleration.  Engines which are subject to varying 
>> loads, can benefit from the retard mechanism if there is any kind of 
>> control valve /butterfly on the >intake, which would alter the manifold 
>> vacuum.
>
> My genset engine is a  1949 Hillman engine, one of the early higher 
> compression engines  (8:1) out of the UK. The vacuum advance and retard is 
> disconnected, but we have not noticed any problems across a wide range of 
> outputs for 1,000's of hours. It is a moot point however, and I will 
> reconnect it next time I play to see if it makes any difference.
>>
>> Anyone setting the timing on an engine with a fixed load-speed, needs to 
>> be sure the advance/retard mechanisms are either working correctly or 
>> have been locked up. As fixed speed engines can "hunt" if there is any 
>> faults in or if there is any small changes in the loading or fuel supply.
>
> Gensets have to operate at fixed speed, so use a governor on the throttle 
> butterfly, and as I said, our advance/retard control is disconnected, so 
> cannot in any way affect how the engine hunts on load or gas changes. 
> Producer gas has many surprises as an engine fuel, and we learn more by 
> the day.
>
> Most of the above comments apply to fixed speed (RPM) applications used 
> for electrical power generation, both base and variable loads, from our 
> installation experiences 1978- 2010.
>
> Doug Williams,
> Fluidyne Gasification.
>
>
>
>
>
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> ------------------------------
>
> Message: 6
> Date: Thu, 24 Feb 2011 20:41:40 -0500
> From: "Bill Klein" <Bill_Klein at 3iAlternativePower.com>
> To: "doug.williams" <Doug.Williams at orcon.net.nz>,   "Discussion of
>    biomass pyrolysis and gasification"
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <31505D7051154F4884508BAA86A7A50E at bk>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Greetings and a good day to each of you!
>
>
>
> As I read through the most recent postings about the "perfect engine" for 
> our wood gas, I was reminded of a study done a few years ago. Those 
> involved, the authors of the abstract below are quite respected in their 
> field, while pioneering work that has contributed to many of the small 
> successes in our industry.
>
>
>
> Though a bit lengthy, the abstract is quite revealing and may add 
> something to the conversation. Respectfully, Bill Klein - 3i
>
>
>
>
>
>
>
> Biomass and Bioenergy 21 (2001) 61-72
>
> Biomass derived producer gas as a reciprocating
>
> engine fuel-an experimental analysis
>
> G. Sridhar _, P.J. Paul, H.S. Mukunda
>
> Combustion Gasification and Propulsion Laboratory,
>
> Department of Aerospace Engineering,
>
> Indian Institute of Science, Bangalore 560 012, India
>
> Received 28 June 2000; accepted 13 December 2000
>
> ABSTRACT
>
> This paper uncovers some of the misconceptions associated with the usage 
> of producer gas, a lower calorific gas as a reciprocating engine fuel. 
> This paper particularly addresses the use of producer gas in reciprocating 
> engines at high compression ratio (17 : 1), which hitherto had been 
> restricted to lower compression ratio (up to 12 : 1). This restriction in 
> compression ratio has been mainly attributed to the auto-ignition tendency 
> of the fuel, which appears to be simply a matter of presumption rather 
> than fact. The current work clearly indicates the breakdown of this 
> compression ratio barrier and it is shown that the engine runs smoothly at 
> compression ratio of 17: 1 without any tendency of auto-ignition. 
> Experiments have been conducted on multi-cylinder spark ignition engine 
> modified from a production diesel engine at varying compression ratios 
> from 11:5: 1 to 17: 1 by retaining the combustion chamber design. As 
> expected, working at a higher compression ratio turned out to
> be more efficient and also yielded higher brake power. A maximum brake 
> power of 17:5 kWe was obtained at an overall efficiency of 21% at the 
> highest compression ratio. The maximum de-rating of power in gas mode was 
> 16% as compared to the normal diesel mode of operation at comparable 
> compression ratio, whereas, the overall efficiency declined by 32.5%. A 
> careful analysis of energy balance revealed excess energy loss to the 
> coolant due to the existing combustion chamber design. Addressing the 
> combustion chamber design for producer gas fuel should form a part of 
> future work in improving the overall efficiency. c_ 2001 Elsevier Science 
> Ltd. All rights reserved.
>
> Keywords: Biomass; Compression ratio; De-rating; Producer gas; Spark 
> ignition engine
>
>
>
> 1. Introduction
>
> With the renewed interest in biomass energy by necessity, biomass-based 
> technologies are achieving prominence not only as rural energy devices but 
> also as industrial power plants. Gasification is one such process
>
> ? Corresponding author. Tel.: +91-80-360-0536; fax: +91-80-3601692.
>
> E-mail address: gsridhar at cgpl.iisc.ernet.in
>
> (G. Sridhar).
>
> where clean gas could be generated
>
> using a wide variety of bio-residues as the
>
> feed stock and in turn use the fuel gas for power generation purposes. 
> These are being used in standard diesel engines in dual-fuel mode of 
> operation so as to obtain diesel savings up to 85%. Operation of engines 
> on gas alone has been explored in some limited sense by a number of 
> researchers ever since World War II. In the
>
> present times, adopting these technologies has immense economic benefits; 
> a route pursued by a number of researchers is in [1-5].
>
> Development of gas engines using producer gas has been explored ever since 
> World War II. It is estimated that over seven million vehicles in Europe, 
> Australia, South America and Pacific Islands were converted to run on 
> producer gas during World War II. These engines were spark ignited 
> engines, mostly in the lower compression ratio bracket operating either on 
> charcoal or biomass derived gas. Extensive fieldwork has been carried at 
> National Swedish Testing Institute of Agricultural Machinery [1] by 
> mounting gas generator and engine set on trucks and tractors. There have 
> also been sporadic installations at Paraguay and Sri Lanka [1] for power 
> generation application.
>
> The question of power generation using producer gas has been addressed in 
> recent times by a few researchers [1, 2, 6] and attempts have been made to 
> convert standard compression ignition engine to a gas engine with the 
> relaxation imposed on the compression ratio (CR) and others [3] operating 
> a supercharged SI engine to realize the rated output. Also, one researcher 
> [4] has reported working on producer gas fuelled engine at high CR (16:5: 
> 1) for water pumping application without any sign of knock. There appears 
> no earlier work on a systematic study on the engine behavior using 
> producer gas fuel. The other important reason that appears responsible is 
> the non-availability
>
> of standard and proven gasification systems, which could generate gas of 
> consistent quality on a continuous basis for engine applications.
>
> Systematic studies are essential from the viewpoint of establishing the 
> highest useful compression ratio (HUCR) for producer gas fuel and also 
> indirectly establish the octane rating for the fuel. This paper reports 
> work on a producer gas fuelled spark ignition
>
> engine converted from a production diesel engine.
>
> A well researched, tested and an industrially proven gasifier system 
> capable of generating consistent quality was employed as the gas generator 
> for testing
>
> purpose [7, 8]. The engine has been tested and verified at the highest 
> compression ratio of 17: 1 in order to establish knock-less performance by 
> capturing the pressure-crank angle trace. Subsequently the engine has been 
> tested at varying CRs so as to arrive at an optimum CR for maximum brake 
> power and affiance. The overall energy balance has been analyzed and the 
> shortcomings identified. Also the emission levels in terms of CO and NO 
> have been examined.
>
> 2. Misconceptions and clarification
>
> Prior to this development there have been two misconceptions regarding 
> producer gas fuel and they are identified as follows: (1) auto-ignition 
> tendency at higher CR when used in reciprocating engine, (2) large 
> de-rating in power due to calorific value of the fuel being low.
>
> It was thought that these perceptions had no reasonable basis. Indeed, the 
> basis for the contrary seemed to exist. Firstly, producer gas being a 
> mixture of many gas species with large fraction being inert should have 
> higher octane rating when compared to natural gas and biogas. The gas 
> contains a large fraction of inert gases like CO2 and N2 accounting to 
> 12-15% and 48-50%, respectively, and these could act as knock suppressors 
> [9]. However, so far there has not been any research of octane rating test 
> conducted on producer gas fuel. Moreover, it is not clear if any 
> established test procedure exists for producer gas like the Methane number 
> test for natural gas and biogas. One crude way of assessment is to test 
> the fuel gas in standard engines and place them accordingly in the octane 
> rating table.
>
> Secondly, there is a general thinking that producer gas being a lower 
> calorific fuel, the extent of de-rating would be large when compared to 
> high calorific value fuels like natural gas (NG) and liquefied petroleum 
> gas (LPG). The de-rating if any could be due to two possible reasons. 
> Firstly, with the lower energy density fuels there is a net decrease in 
> number of molecules when compared to high-energy fuels like diesel, 
> gasoline, NG or LPG. This contributes to some de-rating in case of low 
> energy density fuels [10]. De-rating of power on account of calorific 
> value will be small because of marginal differences in the energy release 
> per unit mixture (air+fuel gas) [11]. This can be explained as follows. 
> The calorific value of producer gas varies between 4.7 and 5:0 MJ N m?3 as 
> against 30 MJ N m?3 for NG. The energy density per unit (producer gas 
> +air) mixture is only 15-20% lower than NG and air mixture even though the 
> calorific value of producer gas is one-eighth of NG. This
> is because the stoichiometric air=fuel ratio for producer gas is 1.2 as 
> compared to 17 for NG. Hence the extent of de-rating with producer gas 
> would not be marginal compared to NG fuelled operation at comparable 
> operating conditions. This gap could be nullified by working producer gas
>
> at higher CR when compared to NG. The upper limit of CR for NG has been 
> identified to be around 15:8: 1 based on a recent work [10].
>
>
>
>
>
>
>
> 3. Earlier work
>
> Shashikantha et al. [2] has reported related work on a converted diesel 
> engine at CR of 11:5: 1. In addition to the change in CR, the combustion 
> chamber of the original engine i.e. bowl-in piston (hemispherical)
>
> was modified to Hesselman (shallow W) with an aim of achieving a higher 
> level of turbulence by squish rather than swirl. With the above 
> modification a power output of 16 kWe has been reported in gas
>
> made with efficiency in the range of 21-24% against a rated output of 17 
> kWe in diesel mode. However, the same authors [6] subsequently claim a 
> lower output and efficiency of 11:2 kWe and 15%. These authors do discuss 
> the knock tendencies at higher CR but no experimental evidence seems to be 
> provided in support. Measurements have been reported of various parameters 
> including that of exhaust emissions; however no measurements have been 
> made with respect to gas composition, which is considered essential from 
> the viewpoint of establishment of input energy.
>
> The first experimental work in the higher CR range has been reported by 
> Ramachandra [4] on a single cylinder diesel engine (16:5: 1 CR) coupled to 
> a water pump. A power de-rating of 20% has been reported at an overall 
> efficiency of 19% without any signs of detonation. This work does not 
> report any other measurement like the pressure-crank angle diagram in 
> order to rationalize some of the results. Work on gasoline engine 
> operation on producer gas has been reported by Parke [12] with de-rating 
> claims of 34%, compared to gasoline operation. The same authors [3] 
> suggest supercharging to
>
> enhance the engine output. Martin and Wauters [5] have reported work using 
> charcoal gas and producer gas on an SI engine with a de-rating of 50% and 
> 40%, respectively, at a CR of 7: 1. However, the same authors claim 20% 
> de-rating when worked with producer gas at a CR of 11: 1. The authors 
> present a CR barrier of 14: 1 and 11: 1 for charcoal and producer gas, 
> respectively, with inadequate experimental justification. >From the 
> literature survey it appears that no experimental evidence is available to 
> support the phenomenon of knock in producer gas engines, even though it is 
> believed knock would occur at higher CR.
>
> 4. Current investigations
>
> It is a well-acknowledged fact that it is desirable to operate an internal 
> combustion engine at the highest possible CR so as to attain higher 
> overall efficiencies. But the gain in efficiency beyond a certain CR can 
> be expected to be marginal due to other influencing factors such as heat 
> loss and friction. In the case of an SI engine the limitation of CR comes 
> from the knock sensitivity of the fuel. It has been experimentally 
> investigated that the upper limit for compression ratio for SI engine 
> operation is 17: 1 beyond which there is a fall in efficiency [13]. The 
> above conclusion
>
> is based on extensive tests with iso-octane as the fuel also doped with 
> anti-knock agent. If one were to consider this as the upper limit and 
> since no other work has been conducted at higher CR for SI engines, 
> choosing a production engine in the above range for the current 
> investigation seemed very appropriate. The current investigation was 
> conducted on a commercially available diesel engine so as to explore the 
> possibility of working at the existing CR of 17: 1 and optimizing the same 
> if required. At the onset of investigation, it was perceived that increase 
> in CR could have conflicting effects on the power output of the engine. 
> This could be explained as follows. It has been universally recognized 
> that turbulent flame speed [9] plays a vital role in the heat release rate 
> during the combustion process in an engine cylinder. The turbulent flame 
> speed can be treated as an enhanced form of laminar flame under the 
> influence of time varying turbulence [9] within the combustion ch
> amber of the engine. The laminar flame speed is again a function of 
> initial pressure, temperature and the mixture composition. An earlier 
> computational work by Mishra [14] indicated that the laminar flame speed 
> for stoichiometric producer gas and air mixture could decrease by 
> one-tenth as the initial pressure is enhanced by a factor of 40. However, 
> these calculations were made at an initial temperature of 300K, and the 
> initial temperature at which combustion starts is high in the case of 
> internal Combustion engines. The influence of initial pressure and 
> temperature on laminar flame speed can be explained in simple terms as 
> follows. The increase in the unburned gas temperature results in increase 
> in adiabatic flame temperature and hence the average reaction rates. The 
> increase in the reaction rate is a result of the increase in the number of 
> radicals released-thus contributing to increase in the flame speed, 
> whereas the rise in pressure can result in reduction in the amount o
> f radicals released thus retarding the flame speed. Therefore, the 
> conflicting nature of the effects of initial pressure and temperature 
> needs to be recognized. The effect of these at varying CR is an additional 
> feature that needs to be recognized in order to arrive at the optimum CR. 
> Consequently, the present investigation was started with an assumption 
> that the optimum compression ratio would be between 12: 1 and 17: 1 for 
> maximum power output and overall efficiency.
>
> In the current investigation, CR was the parameter that was varied. The 
> influence of CR on power, efficiency and emissions has been studied in 
> some detail. Minimum ignition advance for best torque (MBT) has been 
> determined at different Rs. The variation of cylinder pressure with time 
> has been captured using a piezo-based transducer. The overall energy 
> balance has been projected.
>
> 5. Conversion methodologies
>
> A three cylinder, direct injection diesel engine of 3:3 l capacity, with a 
> CR of 17: 1 was converted into a spark ignition engine to drive a 25-kVA 
> alternator. The salient features of the engine are given in Table 1.
>
> Modifications attempted on the engine for conversion are as follows:
>
> 1. Insertion of spark plug in place of fuel injectors without changing its 
> location (centrally located).
>
> 2. Adaptation of a distributor type battery based ignition system with a 
> provision to advance=retard ignition timing. The set ignition timing was 
> checked using a stroboscope.
>
> 3. The combustion chamber design comprising a flat cylinder head and 
> bowl-in piston was retained. No attempts were made to change the 
> combustion chamber design except that the thickness of the cylinder head 
> gasket was varied to accomplish different CRs of 17 : 1, 14:5 : 1, 13:5 : 
> 1 and 11:5 : 1.
>
> 4. For in-cylinder pressure measurement, provision was made on one 
> cylinder head by drilling a 1:5 mm diameter hole for pressure measurement 
> and fitting an optical sensor on the crankshaft for crank angle 
> measurement.
>
> 6. Experimental set-up and measurement scheme
>
> The well-researched, tested and industrial version of IISc's-open top down 
> draft, twin air entry 75 kg h?1 solid bio-residue gasifier system [7] 
> formed the gas generator. This state-of-the art technology has undergone
>
> extensive testing both in India [8] and overseas [15] and proven to be a 
> world-class system. The system has qualified for long hours of continuous 
> operation in meeting the industrial requirements in terms of generation of 
> consistent quality gas. The overall details of the gasifier system are 
> presented in Fig. 1. As shown in the figure, the system had the provision 
> to test the quality of the gas prior to supply to
>
> engine. At the engine intake, a carburetor is provided
>
> the engine. At the engine intake, a carburetor is provided for 
> proportioning air and fuel flow. As there were no carburetors commercially 
> available to cater to producer gas, a locally made carburetion system and 
> manually controlled valve were used for proportioning.
>
> Measurements were made with respect to the following parameters:
>
> (A) Producer gas compositions using on-line gas analyzers. The gases 
> analyzed were CO, CO2, CH4, O2 and H2. The N2 concentration was deduced by 
> difference. The CO, CO2, CH4 components were determined using infrared gas 
> analyzers and the H2 component using a thermal conductivity-based 
> analyzer. The O2 measurement system was based on chemical cell.
>
> (B) In-cylinder pressure variation data synchronized with the crank angle 
> measurement was acquired
>
> on a computer for every one-degree crank angle.
>
> The pressure measurement was accomplished using
>
> a pre-calibrated Piezo based pressure transducer
>
> (M=s PCB make).
>
> (C) Measurement of voltage and current across
>
> three phases and frequency for power output
>
> calculations-the load bank constituted of resistors.
>
> (D) Air and gas Kow to the engine using pre-calibrated
>
> venturimeters.
>
> (E) Engine exhaust analysis-O2, CO2; CO, and NO
>
> and temperature.
>
> with the crank angle measurement was acquired
>
> on a computer for every one-degree crank
>
> on a computer for every one-degree crank angle. The pressure measurement 
> was accomplished using a pre-calibrated Piezo based pressure transducer 
> (M=s PCB make).
>
> (C) Measurement of voltage and current across three phases and frequency 
> for power output calculations-the load bank constituted of resistors.
>
> (D) Air and gas FLow to the engine using pre-calibrated venturimeters.
>
> (E) Engine exhaust analysis-O2, CO2; CO,
>
> and NO and temperature.
>
> 7. Experimental procedure
>
> Experiments were initiated on the engine only after the gasifier system 
> stabilized i.e. attained steady state operation in terms of generation of 
> consistent quality gas. The typical time scale for attaining steady state
>
> of operation from the cold start was 2-3 h. During this period the gas was 
> flared in a burner. The gas composition was determined using on-line gas 
> analysers, pre-calibrated using a known producer gas mixture. The 
> calibrations of these analyzers were checked at random time intervals so 
> as to minimize errors in long duration operation. Typically gas 
> composition at the time of start of the engine test was 19 ? 1% H2; 19?1% 
> CO; 2% CH4; 12?1% CO2; 2?0:5% H2O and rest, N2. The mean calorific value 
> of gas varied around 4:65?0:15 MJ N m?3. The feedstock used for 
> gasification is Causurina species wood with moisture content between 12% 
> and 15% on dry basis (sun-dried wood).
>
> Once the gas composition stabilized, the engine was operated for a few 
> minutes at 1500 RPM at no-load condition. All the tests on the engine were 
> conducted around a constant speed of 1500?50 RPM. The throttling for speed 
> control and air and fuel proportioning was achieved using manually 
> operated valves.
>
> Experiments were conducted at CRs of 17: 1, 14:5: 1, 13:5: 1 and 11:5: 1 
> and these CRs were achieved by varying the thickness of the cylinder head 
> gasket. The compression ratio values are based on the cylinder's geometric 
> measurements and were verified by matching the motoring curve with an 
> engine simulation curve. The engine was tested at different ignition 
> timing settings to determine the MBT at different CRs. With set ignition 
> timing, the air and fuel were tuned to achieve maximum power. Measurements 
> were initiated 10-15 min after attaining stable operation. The in-cylinder 
> pressure data with a resolution of 1? crank angle was acquired on a 
> computer in excess of 100-150 consecutive cycles. Prior to the start of 
> these tests, the TDC was accurately determined using a dial gauge and 
> synchronized with the optical crank angle measuring system with an 
> accuracy of ?0:5?.
>
> 8. Results and observations
>
> 8.1. Performance
>
> The first and the foremost result of these tests is that the engine worked 
> smoothly without any sign of knock at a high CR of 17: 1. There was no 
> sign of audible knock during the entire load range. Moreover, the absence 
> of knock was clear from the pressure-crank angle recordings both at full 
> load and part load.
>
> The engine delivered a maximum output of
>
> 17:5 kWe (20 kW shaft power) at a CR of 17: 1 with an overall efficiency 
> of 21% compared to 21 kWe (24 kW shaft power) output at 31% efficiency in 
> diesel mode. The overall efficiency calculated is based on the ratio of 
> the shaft output delivered to the energy content in the biomass. The 
> overall efficiency in gas mode is based on the ratio of mechanical shaft 
> output to the energy content in the biomass. The useful output and 
> efficiency decreased with the lowering of CR. A maximum output of 15:3 kWe 
> (17:6 kW shaft power) at an overall efficiency of 18% was obtained at a CR 
> of 11:5: 1. The variation of brake power with CR is shown in Table 2. The 
> power output at an intermediate CR of 14:5: 1 and 13:5: 1 were 16.4 and 
> 16:2 kWe, respectively, and with overall efficiencies being 20%. The 
> overall efficiency at 13.5 CR is the same as that at 14:5: 1 on account of 
> leaner operation.
>
> The extent of de-rating in brake power is about 16.7% at a CR of 17: 1 and 
> increased as high as 26% at 11:5: 1 when compared to diesel mode of 
> operation. The gain in overall efficiencies from CR 11.5 to 17: 1 works 
> out to be 16.6%, which means an increase of 3% per unit CR increment. 
> However, the incremental gain per unit CR from 14.5 to 17: 1 is 2%. These 
> figures are well within the range of 1 to 3% gains per unit incremental of 
> CR [9]. The fuel-air equivalence ratio (PHI) at which the maximum power 
> was derived was around 1.00-1.06 with the exception of 0.86 at CR of 13:5: 
> 1. The air to fuel ratio is tuned from the viewpoint of deriving maximum 
> output and therefore the efficiency figures are necessarily not the 
> maximum that can be obtained. It may be possible to achieve higher overall 
> efficiencies by operating at leaner conditions.
>
> The peak shaft output at varying CR was found to be sensitive to the 
> producer gas composition. The hydrogen fraction in the fuel gas dictated 
> the ignition timing setting. Therefore the minimum advance for brake 
> torque (MBT) varied with the change in hydrogen content in the fuel gas. A 
> higher fraction of hydrogen means that the ignition timing has to be 
> retarded in order to benefit from the increase in the flame speed. With a 
> faster burn rate the optimum spark timing has to be closer to the TDC, the 
> mixture temperature and pressure at the time of initiation of spark will 
> be higher and hence the laminar flame speed at the start of combustion 
> will also be higher. Therefore optimizing the ignition timing based on 
> hydrogen fraction is vital from the viewpoint of deriving maximum shaft 
> output.
>
> Since the mixture flame speed is a strong function of hydrogen content in 
> the gas, the MBT will differ based on the actual fuel gas composition. For 
> a gas composition containing 20:5 ? 0:5% H2 and 19:5 ? 0:5% CO, the MBTs 
> have been identified as shown in Table 2, the measurement accuracy of MBT 
> is within 3? crank angle. The MBT in the present case has turned out to be 
> about 6-10? BTDC at a CR of 17: 1 and has gone up to as high as 14-16? 
> BTDC for a CR of 11:5: 1. These values are much lower compared to 30 to 
> 40? BTDC at a CR of 11.5 based on earlier work [2, 6, 12] but matches with 
> 10? BTDC [4] at a CR of 17: 1.
>
> The mechanical efficiency of the engine at a CR of 17 : 1 is about 80% and 
> increases to as high as 87% at a CR of 11:5 : 1. The increase in 
> mechanical efficiency is attributed to the reduction in rubbing friction 
> [16] due to lower cylinder pressures encountered at lower CRs. The 
> mechanical efficiency values are based on indicated power measurement 
> (based on integration of pressure-volume diagram) and these were found to 
> be identical with the Morse test results.
>
> 8.2. Pressure-crank angle data
>
> The pressure-crank angle recording at all the CRs did not show any trace 
> of knock for all ranges of load including that of peak load and this is 
> visible from the pressure-crank angle diagrams as shown in Fig. 2. Faster 
> burn rate due to presence of hydrogen in the fuel gas may be one factor 
> for the non-knocking performance at higher compression ratio. The faster 
> burn rate accompanied by retarded ignition timing setting obviates any 
> auto-ignition tendency of the end gas. Increasing the flame speed or 
> retarding the ignition timing setting is one possible way of reducing 
> knock tendency and this is well acknowledged in the literature [9]. The 
> maximum indicated mean effective pressure (IMEP) was obtained at ignition 
> timing corresponding to the maximum shaft output. The IMEP obtained at 
> varying CR as a function of ignition timing is shown in Fig. 3. The max 
> IMEP recorded was 595 kPa at a CR of 17: 1 and declined to about 485 kPa 
> at a CR of 11:5: 1. The maximum IMEP was obtained at a
>  PHI of 1.05 and this falls well within the anticipated PHI of 1.0 to 1.1 
> [9]. The point of occurrence of peak pressure at all CRs occurred at 
> 18-19? ATDC, except that at 13:5: 1 which occurred at 17? ATDC, which is 
> close to the generally acknowledged value of 17?ATDC for MBT [9, 17]. 
> Therefore, for CR of 17: 1, 14.5 and 11:5: 1 the MBT should be more 
> advanced
>
>
>
> (lie within 2-3?) from what was actually measured. The variation of IMEP 
> or the net useful output within this close range would be marginal. The 
> peak cylinder pressures and their point of occurrence is shown in Table 3. 
> The peak pressure at 14:5: 1 CR is lower than 13:5: 1 probably due to a 
> slight departure from MBT. The coefficient of variation of the IMEP at all 
> CRs and ignition settings occurred well within 3-3.5%, implying low 
> cycle-to-cycle variation. The reason for low cyclic variation is the 
> faster rate of combustion occurring inside the engine cylinder. The faster 
> rate of combustion is attributed to higher flame speeds due to the 
> presence of hydrogen in the gas and also to the bowl-in piston combustion 
> chamber design with increased
>
> squish effect.
>
> 8.3. Energy balance
>
> Fig. 4 represents the overall energy balance at a CR of 17: 1. The energy 
> balance at MBT showed that about 32.5% of the energy was realized as 
> useful output (indicated power); about 27% was lost through the exhaust 
> (including the CO in the exhaust) and the remaining 40% to the cooling 
> water (inclusive of radioactive losses, etc). As expected with the 
> advancement of ignition timing, the loss through exhaust mode reduced and 
> increased to the coolant route. The energy balance in gas mode showed that 
> a large fraction of
>
> the energy was lost to the cooling water when compared to the diesel mode. 
> Fig. 5 compares the energy balance in gas and diesel mode (at rated output 
> of 21 kWe) at a CR of 17 : 1, the energy loss at maximum power delivered 
> to the coolant and miscellaneous is about 40% compared to 33% in diesel 
> and whereas, the energy loss through exhaust in gas mode decreased by 5%. 
> The indicated power and thereby the thermal efficiency being higher in 
> diesel mode is evident from the pressure-time curve shown in Fig. 2. The 
> energy balance
>
> at varying CRs is shown in Fig. 6. There was an increase in the loss of 
> energy through exhaust (which includes the energy in the form of CO) with 
> the reduction in the CR, whereas, the loss through the coolant and 
> miscellaneous was higher at higher CR. The useful energy is 32.5% at a CR 
> of 17: 1 and has declined to 25.7% at a CR of 11:5: 1. The useful energy 
> at a CR of 13:5: 1 has stood about the same as that at 14:5: 1 due to a 
> relatively leaner operation. The increased amount of heat loss to the 
> cooling water as a whole in gas operation
>
> could be attributed to the engine combustion chamber design. It has been 
> quoted in the literature [9] that with engine geometries such as 
> bowl-in-piston there will be 10% higher heat transfer. The heat transfer 
> to the coolant in the current case falls well within this range. With the 
> increase in compression ratio the overall conversion efficiencies must 
> improve thermodynamically, similarly, the heat loss to the coolant and 
> exhaust should have reduced. However, increased energy loss to the coolant 
> at a higher compression
>
> ratio is probably due to increase in heat transfer coefficient.
>
> accounted for because it forms a small part (_ 5%) of NOx generated [9]. 
> The NO level has been represented in milligram per unit MJ of input 
> energy. These results have been compared to the Swiss norms because of 
> some earlier collaborative work with the
>
> Swiss scientists; it was indicated that Swiss norms were stringent with 
> respect to the emission levels. The NO level reduced with the retardation 
> of ignition timing and this feature was observed for all CRs. The
>
> NO level was observed to be maximum at the highest compression ratio with 
> advanced ignition timings, whereas for the MBT range of 6-20? BTDC the NO 
> was roughly about the same in almost all the cases. However, there was one 
> exception of NO being higher at MBT for a CR of 13.5 due to a leaner 
> operation.
>
> It is a well-known fact that NO generation is strongly dependent on the 
> temperature and also residence time in the combustion chamber. With the 
> flame speed of the gas mixture being high, the ignition setting is 
> retarded whereby the residence time in the high temperature combustion 
> chamber is automatically reduced. Therefore, the low NO levels at retarded 
> ignition setting is an expected and consistent behavior. The above results 
> match well with those quoted in the literature [9], which show small to 
> modest variation of NO with CR. The variation of carbon monoxide (CO) with 
> PHI is shown in Fig. 8. The CO levels have been represented in grams per 
> MJ of input energy. The trend of CO with PHI is clear from the figure. The 
> CO levels were lower at the highest CR, and this could be attributed to 
> higher temperatures, leading to relatively complete combustion.
>
> 9
>
> Been smooth and it has been established beyond doubt that the operating 
> engines using producer gas in SI mode at higher compression ratios is 
> technically feasible. The cylinder pressure-crank angle trace has shown 
> smooth pressure variations during the entire combustion process without 
> any sign of abnormal pressure raise. A shorter duration of combustion has 
> been observed with producer gas fuel, requiring
>
> retardation of the ignition timing to achieve MBT. These faster burning 
> cycles are corroborated by low cyclic pressure fluctuations with a 
> coefficient of variation 3%. The faster burning process has been 
> identified to be due to the higher flame speed of the fuel gas mixture and 
> the same
>
> h
>
> content in the gas. So, increased quantity of hydrogen in the fuel gas 
> mixture is desired from the viewpoint of approaching an ideal cycle 
> operation. The perceived
>
> negative influence of pressure on flame speed at higher CR does not seem 
> to exist based on the above results. The maximum de-rating in power is 
> observed to be 16% in gas mode when compared to diesel operation at 
> comparable CR. The extent of de-rating was much lower when compared to any 
> of the previous studies [3-6]. This number matches with a similar kind of 
> de-rating reported with NG operation [10]. However, the overall efficiency 
> drops down by almost 32.5% compared to normal diesel mode of operation. A 
> careful analysis of the energy balance revealed excessive heat loss to the 
> coolant at all CRs and this resulted in engine overheating within 30-40 
> min of operation at full load. This phenomenon of excessive heat loss 
> could be attributed to bowl-in piston combustion chamber design. Higher 
> heat loss to the cylinder walls can be expected because the combustion 
> chamber is originally meant for diesel operation with inherent swirl. 
> Hence suitable modification of the combustion cham
> ber is essential from the view point of reducing the energy loss to the 
> coolant. Reduction in 10% heat loss to the coolant would amount to 
> improvement in overall efficiencies by 3%. The study of the engine 
> combustion chamber and modifications can be looked upon as future work.
>
> R
>
> [1
>
> mechanical wood products branch of FAO forestry paper No. 72, Food and 
> Agriculture Organization of United Nations, Rome, 1986.
>
> [2
>
> GS, Kamat PP, Parikh PP. Development and performa
>
> 15 kWe producer gas operated SI engine. Proceedings of Fourth National 
> Meet on Biomass Gasification and Combustion, Mysore, India, vol. 4, 1993. 
> p. 219-31.
>
> [3
>
> Biomass producer ga
>
> Engines-naturally aspirated and supercharged engines. Michigan: American 
> Society of Agricultural Engineers, 1981. p. 1-35.
>
> [
>
> Performance studies
>
> engine. Proceedings of Fourth National Meet on Biomass Gasification and 
> Combustion, Mysore, India, vol. 4, 1993. p. 213-8.
>
> [5
>
> Performance of charcoal
>
> combustion engines. Proceedings of International Conference-New 
> EnergConversion Technologies and their Commercialization's, vol. 2, 1981. 
> p24.
>
> [6
>
> Veerkar S. Design dev
>
> spark ignited producer gas engine. Proceedings of the XIV National 
> Conference on IC Engines and Combustion, Pune, India, 1995. p. 97-107.
>
> [7
>
> Open-top wood gasifiers, renewable
>
> energy-sources for fuels and electricity. Washington, DC: Island Press, 
> 1993.
>
> [8
>
> Shrinivasa U, Sharan H. Results of an Indo-Swi
>
> qualification and testing of a 300-kW IISc-Dasag gasifier. Energy for 
> sustainable development, vol. 4, November 1994. p. 46-9.
>
> [9
>
> Internal combustion e
>
> International edition. New York: McGraw-
>
> Hill, 1989.
>
> [1
>
> Development of a natural
>
> engine for optimum performance. Proceedings of institution of mechanical 
> engineers, Part D, vol. 211, 1997. p. 361-78.
>
> [1
>
> Fuels from biomass and their rational utilization in internal combustion 
> engines.
>
> Proceedings of International Conference-New Energy Conversion Technologies 
> and their Commercialization's, vol. 2, 1981. p. 1334-40.
>
> [12] Parke PP, Stanley SJ, Walawnder W. Biomass producer gas fuelling of 
> internal combustion engines. Energy from Biomass
>
> and Wastes V, Lake Buena Vista Florida. p. 499-516.
>
> [13] Caris DF, Nelson EE.
>
> A new look at high compression engines. SAE Transactions 1959; 67:112-23.
>
> [14] Mishra DP, Paul PJ, Mukunda HS. Computational studies on the flame 
> propagation in producer gas-air mixture and experimental comparisons, 
> Proceedings of the XIII National Conference on IC Engines and Combustion, 
> Bangalore, India,
>
> 1994. p. 256-62.
>
> [15] Giordano P.
>
> Experience on running a wood based cogeneration power plant with the 
> IISc-Dasag gasifier. Biomass Users Network (BUN-India), vol. 3(2), October 
> 1999. p. 2.
>
> [16] Gish RE, McCullough JD, RetzloD JB, Mueller HT.
>
> Determination of true engine friction. SAE Transactions 1958; 66:649-67.
>
> [17] Wu CM, Roberts CE, Matthews RD, Hall MJ.
>
> Effects of engine speed on combustion in SI engines: Comparison of 
> predictions of a fractal burning model with experimental data, SAE Trans. 
> 1993; p. 2277-91.
>
>
>
>  ----- Original Message ----- 
>  From: doug.williams
>  To: Discussion of biomass pyrolysis and gasification
>  Sent: Thursday, February 24, 2011 7:46 PM
>  Subject: Re: [Gasification] ideal wood gas engine
>
>
>  Hi Tony and Colleagues
>
>  > This may be my first post to this site, I trust you will all not hope 
> it is my last.
>
>  As a fellow New Zealander, lets hear more from you, we cover a lot of 
> engine "stuff", and new voices are most welcome.
>
>  > Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
> sparkplug is the best way to really know when you have the correct mixture 
> as you can see the flame color within the combustion chamber.
>
>  Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it to 
> teach how exhaust temperatures and engine sound changed across gas/air 
> mixtures, using a single cylinder Iron Horse engine. I sent both Kevin and 
> Arnt a copy of the colour guide out of our kit, seeing as they were 
> interested in this subject.
>
>  > A turbocharger can be used to increase the volume of mixture which is 
> drawn into engine but whether or not they are practical given the 
> possibility of contaminated gas is something I cannot comment on.
>
>  This is a problem for producer gas in most DIY systems. We do better at 
> the commercial level with more sophisticated filtration systems, but it is 
> better to use naturally aspirated engines of larger cylinder capacity of 
> lower RPM, than undersized turbocharged engines relying on high RPM for 
> DIY projects.
>
>  > The Mean effective pressure within the engine during the combustion 
> stroke, is largely dependent on the length of stroke of the engine, the 
> compression ratio and the ignition timing.
>  > The stroke cannot easily be altered but the compression ratio can be 
> changed on some engines by machining the cylinder head.
>
>  Generally speaking, this would mainly be applied to very old engines, 
> probably pre-dating around 1949. The literature records a lot of work in 
> this area of compression ratios by Woods in the late 1930's early 40's 
> (from memory), where it was established that around 11:1 was the optimum 
> for producer gas. At this point, the extra friction from compressive 
> forces consumed the "extra energy", and little was gained from higher 
> compression.
>
>  > If a petrol (spark ignited) engine is run on wood gas or any other gas, 
> the Ignition timing has to be altered.  In general the ignition timing 
> will be advanced by several degrees, in order to ensure as high a mean 
> pressure as possible is reached during the combustion stroke.
>
>  This is true, but remember that WW2 petrol was of lower octane, and 
> required ignition advancement. Modern engines have that advancement 
> already built in for the higher octane available today. Then, separate 
> charcoal gasifiers away from wood gasifiers, because the H2 content again 
> changes ignition behaviour. Most engines set up to operate on LPG or 
> natural gas, are from 10-12:1 compression ratio (of the smaller sizes), 
> and run without alteration on 110-120 octane producer gas perfectly. 
> Having said that, you can always tweak them if the situation demands that 
> degree of perfection. The engine is the least of your worries if the gas 
> making is unstable (:-)
>
>  > The benefit of using a computer controlled ignition system is that most 
> if not all computer controlled systems have a "knock" sensor.  The purpose 
> of this device is to sense when the ignition of the fuel has caused the 
> pressure within the cylinder to rise so high that the remaining un burnt 
> fuel spontaneously explodes.  This results in engine knock, the resulting 
> noise is commonly known as "pinking"   Diesel engines knock a lot of the 
> time because the very design of the engine is to raise the fuel 
> temperature to point when it spontaneously burns.
>
>  Speaking "generally", producer gas has no problem in most standard spark 
> ignition engines, as the spontaneous ignition temperature for producer gas 
> in our experience, is around 600C. You find these compression temperatures 
> in diesels around 16:1 ratio, and again from experience, once you go over 
> 17:1, the spontaneous ignition temperature makes the engine very unstable. 
> We worked with Lister (NZ)  to develop dual fuel conversion kits for the 
> Pacific region, converted to gas Ford diesels in the UK, Ford natural gas 
> engines in USA, and purpose built gas engines in Germany.
>
>  In all cases, the operating temperatures around the engine can affect the 
> behaviour of the ignition temperatures, as will the actual CO,H2, and CH4 
> content. Any uncracked hydrocarbons will also affect the timing behaviour, 
> so be careful how you tinker with the timing. Nothing is written in stone!
>
>  > Older engines that use a Distributor lack the anti-knock feature. 
> Commonly distributors have a simple mechanical advise mechanism, to 
> advance the ignition as the engine revs faster, and a >Vacuum Retard 
> mechanism which aids acceleration.  Engines which are subject to varying 
> loads, can benefit from the retard mechanism if there is any kind of 
> control valve /butterfly on the >intake, which would alter the manifold 
> vacuum.
>
>  My genset engine is a  1949 Hillman engine, one of the early higher 
> compression engines  (8:1) out of the UK. The vacuum advance and retard is 
> disconnected, but we have not noticed any problems across a wide range of 
> outputs for 1,000's of hours. It is a moot point however, and I will 
> reconnect it next time I play to see if it makes any difference.
>  >
>  > Anyone setting the timing on an engine with a fixed load-speed, needs 
> to be sure the advance/retard mechanisms are either working correctly or 
> have been locked up. As fixed speed engines can "hunt" if there is any 
> faults in or if there is any small changes in the loading or fuel supply.
>
>  Gensets have to operate at fixed speed, so use a governor on the throttle 
> butterfly, and as I said, our advance/retard control is disconnected, so 
> cannot in any way affect how the engine hunts on load or gas changes. 
> Producer gas has many surprises as an engine fuel, and we learn more by 
> the day.
>
>  Most of the above comments apply to fixed speed (RPM) applications used 
> for electrical power generation, both base and variable loads, from our 
> installation experiences 1978- 2010.
>
>  Doug Williams,
>  Fluidyne Gasification.
>
>
>
>
>
>
> ------------------------------------------------------------------------------
>
>
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>
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> ------------------------------
>
> Message: 7
> Date: Thu, 24 Feb 2011 18:59:22 -0800
> From: dave <oldbeeman at comcast.net>
> To: "doug.williams" <Doug.Williams at orcon.net.nz>,   Discussion of
>    biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <4D671B0A.2000703 at comcast.net>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> hi doug.
> i would have to take it from this post that you have survived the
> troubles in your country.
>
> dave
>
>
> doug.williams wrote:
>> *Hi Tony and Colleagues
>>
>> *> T
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> ------------------------------
>
> Message: 8
> Date: Fri, 25 Feb 2011 16:25:04 +1300
> From: "doug.williams" <Doug.Williams at orcon.net.nz>
> To: "dave" <oldbeeman at comcast.net>, "Discussion of biomass pyrolysis
>    and gasification"   <gasification at lists.bioenergylists.org>
> Subject: [Gasification] NZ Earthquake, OT
> Message-ID: <42B0BFFBB44342D0A1CF8B9F2F8106E2 at dougspc>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Dave,
>
> Yes, what a tragedy after Christchurch surviving last Septembers 
> earthquake without any loss of life. I live North of Auckland city in the 
> North Island, and a long way from the trouble. If we have anything here, 
> it will be volcanic eruption, and a nasty situation for all. NZ is on the 
> edge of the Pacific Plate and ring of fire, so there is potential for a 
> lot of ongoing tragedy in this part of the World.  As a small country, our 
> government encourage us to have a earthquake box prepared just in case, as 
> little warning of any value can be assured. Most I talk to just cannot 
> imagine the need, so hope that will at least change now with such a nasty 
> wake-up call.
> ..
> Thanks for the kind thoughts, and help from the emergency response teams 
> arriving from many countries.
> Regards,
> Doug.
>
>
> hi doug.
> i would have to take it from this post that you have survived the troubles 
> in your country.
>
> dave
>
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> ------------------------------
>
> Message: 9
> Date: Thu, 24 Feb 2011 23:19:56 -0800
> From: "Luke Gardner" <lgardner at wwest.net>
> To: "Discussion of biomass pyrolysis and gasification"
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <EEBB12C86C7D49C1980B3B64A3287897 at santashelper>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>    reply-type=original
>
> Tony,
> you discussed:
>
> "The Mean effective pressure within the engine during the combustion 
> stroke,
> is largely dependent on the length of stroke of the engine, the 
> compression
> ratio and the ignition timing."
>
> I beg to differ,  the obective is to hit the " hit the nail on the head" 
> for
> each combustion stroke with correct ignition timing.
>
> the stroke does come into it as the flame front is chasing the piston down
> through the  combustion stroke, so the longer the stroke the further it
> travels through 90 degrees crank rotation. thus lengthening its burn to 
> peak
> push time.
>
> The two really important factors to consider are RPM and fuel burn rate.
> different fuels have different burn rates, commonly linked to its octane.
>
> due to the simple geometry of the crank and rod there is a "sweet spot"
> during a combustion stroke that provides the greatest mechanical advanage
> for a piston to create mechanical energy from pressure above it. It is at
> this instant that you want the peak effective pressure.
>
> without going into too many details I would have to dig up,  this is the
> jist,
>
> at 1800 rpm the crank will turn 90 degrees in .0083 seconds
> at 3600 rpm the crank will turn 90 degrees in  .0042 seconds
>
> Some fuels burn slow and some fast, the fuels if uniform to themselves 
> will
> burn at a calculable speed measured in time.
> whatever that time is it takes to go from ignition to peak push it would 
> be
> desirable to back the crankshaft up that amount of time (which is further
> advanced the higher the rpm, more degrees of "back up") and strike that
> match in anticipation of hitting that sweet spot with peak push.
>
> swing to early and you hit the ball,, its just a foul,  too early and the
> piston loads improperly and cocks in the bore, only to violently shift to 
> it
> is loaded properly position once the rod swings through tdc.....  and you
> have piston clatter, or preignition, or pinging, whatever you want to call
> it,  its the same thing.  Put a set of pistons in backwards and you will
> have it all the time unless you advance the timing too far and it will
> preignite and the constant clatter will go away,,,, if you got lucky 
> enough
> to have your valves clear it.
> swing to late and you hit the ball,, its just a foul the other way,, 
> this
> would be "detonation" and from what i understand, it is a silent killer of
> engines something to do with the combine forces of the mass of the
> piston/rod and it still loaded with explosion pressure destroys the rod
> bearings.
>
> proper ignition timing  control is manditory  for optimising engine
> preformance and life.
> for a fixed rpm engine it can be fixed, but it sure would fire up nicer if
> it had some flex for low rpm cranking speeds.
>
> Luke Gardner
>
>
>
> ----- Original Message ----- 
> From: "Tony.Batchelor" <Tony.Batchelor at tekura.school.nz>
> To: "'Discussion of biomass pyrolysis and gasification'"
> <gasification at lists.bioenergylists.org>
> Sent: Sunday, February 20, 2011 6:47 PM
> Subject: Re: [Gasification] ideal wood gas engine
>
>
>> Dear Kelvin and members.
>>
>> This may be my first post to this site, I trust you will all not hope it
>> is my last.
>>
>> Engine power output is a complex issue,  factors such as the energy
>> density of the fuel, the air/fuel ratio that enters the engine, the 
>> volume
>> of air/fuel which is able to enter the engine during the induction 
>> stroke,
>> and the compression pressure reached prior to ignition and the mean
>> pressure reached during the combustion stroke are just some of the most
>> important factors.  Besides the detailed design of intake manifold and
>> exhaust pipes which influence how well an engine can breathe.
>>
>> Where an engine is to be run on wood gas alone, it would be better to do
>> away with as many obstructions in the intake manifolds as possible.  The
>> key point being to get as much of the gas/air mixture into the engine.
>> This is one reason why Diesel engines are good as they only have suck in
>> air, as fuel is added internally.  Fuel injected petrol engines come 
>> close
>> behind, carburetor models are generally more restricted as air passes
>> through the carburetor.
>>
>> Getting the Air/fuel ratio correct is also vital.  Using a "colortune"
>> sparkplug is the best way to really know when you have the correct 
>> mixture
>> as you can see the flame color within the combustion chamber.
>>
>> A turbocharger can be used to increase the volume of mixture which is
>> drawn into engine but whether or not they are practical given the
>> possibility of contaminated gas is something I cannot comment on.
>>
>> The Mean effective pressure within the engine during the combustion
>> stroke, is largely dependent on the length of stroke of the engine, the
>> compression ratio and the ignition timing.
>> The stroke cannot easily be altered but the compression ratio can be
>> changed on some engines by machining the cylinder head.
>> Altering the intake air pressure, using a turbo or other methods. Such as
>> cooling the intake air/fuel temperature.
>> And by changing the ignition timing.
>> If a petrol (spark ignited) engine is run on wood gas or any other gas,
>> the Ignition timing has to be altered.  In general the ignition timing
>> will be advanced by several degrees, in order to ensure as high a mean
>> pressure as possible is reached during the combustion stroke.
>> The benefit of using a computer controlled ignition system is that most 
>> if
>> not all computer controlled systems have a "knock" sensor.  The purpose 
>> of
>> this device is to sense when the ignition of the fuel has caused the
>> pressure within the cylinder to rise so high that the remaining un burnt
>> fuel spontaneously explodes.  This results in engine knock, the resulting
>> noise is commonly known as "pinking"   Diesel engines knock a lot of the
>> time because the very design of the engine is to raise the fuel
>> temperature to point when it spontaneously burns.
>> Older engines that use a Distributor lack the anti-knock feature. 
>> Commonly
>> distributors have a simple mechanical advise mechanism, to advance the
>> ignition as the engine revs faster, and a Vacuum Retard mechanism which
>> aids acceleration.  Engines which are subject to varying loads, can
>> benefit from the retard mechanism if there is any kind of control valve
>> /butterfly on the intake, which would alter the manifold vacuum.
>>
>> Anyone setting the timing on an engine with a fixed load-speed, needs to
>> be sure the advance/retard mechanisms are either working correctly or 
>> have
>> been locked up. As fixed speed engines can "hunt" if there is any faults
>> in or if there is any small changes in the loading or fuel supply.
>>
>> Tony Batchelor, ex, road transport engineer, now teaching physics.
>> Wellington, New Zealand.
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: gasification-bounces at lists.bioenergylists.org
>> [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Kevin
>> Sent: Monday, 21 February 2011 1:06 p.m.
>> To: Discussion of biomass pyrolysis and gasification
>> Subject: Re: [Gasification] ideal wood gas engine
>>
>> Dear Charles
>>
>> Your stated need is for "about 20 HP" at 1,800 RPM
>>
>> You should be able to get about 21.4 HP with an engine of 2500 CC (153
>> Cubic
>> Inches), burning about 19 kG/Hr (42 Lbs/Hr)
>>
>> It would be very helpful if others could comment on the other aspects of
>> an
>> engine.... in particular, the Ignition system, whether Distributor or
>> "Computer Controlled", and the implications of using a Fuel Injected
>> engine,
>> rather than a carburetor engine.
>>
>> Best wishes,
>>
>> Kevin
>>
>> ----- Original Message -----
>> From: <bayent at ns.sympatico.ca>
>> To: <gasification at lists.bioenergylists.org>
>> Sent: Sunday, February 20, 2011 11:32 AM
>> Subject: [Gasification] ideal wood gas engine
>>
>>
>>>
>>> Content analysis details:   (0.0 points)
>>>
>>>  pts rule name              description
>>> ---- ---------------------- --------------------------------------------------
>>> _SUMMARY_
>>>
>>> Hi All,
>>>
>>> I have several engines to chose from here for my next wood gas project.
>>> Going to go ahead with it and just hope the stink has settled form my
>>> insurance company ripping hair out of their heads. ( hope they are not 
>>> on
>>> here.. bugger )
>>> Besides this is not a heating device so should not count.
>>> What out of the junk yard specials would be considered ideal for wood 
>>> gas
>>> give I Only need this time to come up with 20 hp at 1,800 rpm?
>>> I have everything in the shop for a Mike clone.
>>> Spending a few bucks for the right engine is going to be real cheep just
>>> now.
>>> I am not keen on stuck valves through pistons. ( it that ever happens...
>>> never mind )
>>>
>>> Regards all,
>>> Charles
>>>
>>> _______________________________________________
>>> Gasification mailing list
>>>
>>> to Send a Message to the list, use the email address
>>> Gasification at bioenergylists.org
>>>
>>> to UNSUBSCRIBE or Change your List Settings use the web page
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>>>
>>> for more Gasifiers,  News and Information see our web site:
>>> http://gasifiers.bioenergylists.org/
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 10.0.1204 / Virus Database: 1435/3455 - Release Date: 02/20/11
>>>
>>
>>
>> _______________________________________________
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>
>
>
>
> ------------------------------
>
> Message: 10
> Date: Fri, 25 Feb 2011 08:44:44 +0000
> From: Daniel Chisholm <dmc at danielchisholm.com>
> To: Discussion of biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID:
>    <AANLkTi=GOtT3r0OtKV=zCWPZCWQqrSJdVjMNF1J8rRd2 at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> For what it's worth:
>
>   - preignition, piston clatter (slap), and pinging are three different
>   things
>   - pinging is detonation
>   - a fuel's octane rating is not a measure of its energy content nor of
>   how fast it can be made to burn.  Octane rating is a measure of a fuel's
>   resistance to detonation.  Typically (and counterintuitively) a higher
>   octane fuel is slower burning
>   - burn rate is not a constant, among other things it depends on pressure
>   and temperature, both of which change as a piston moves and also as a
>   function of how much burning has already happened
>
>
> -- 
> - Daniel
> Fredericton, NB  Canada
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> ------------------------------
>
> Message: 11
> Date: Fri, 25 Feb 2011 03:26:36 -0600
> From: Bob Stuart <bobstuart at sasktel.net>
> To: Discussion of biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <84212405-EEF2-45AD-8643-2BA088C07446 at sasktel.net>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> Also, FWIW, the speed of the flame front having to chase the piston
> is not as significant as it might seem, as the gas charge is also
> chasing the piston.
>
> Bob
>
> On 25-Feb-11, at 2:44 AM, Daniel Chisholm wrote:
>
>> For what it's worth:
>> preignition, piston clatter (slap), and pinging are three different
>> things
>> pinging is detonation
>> a fuel's octane rating is not a measure of its energy content nor
>> of how fast it can be made to burn.  Octane rating is a measure of
>> a fuel's resistance to detonation.  Typically (and
>> counterintuitively) a higher octane fuel is slower burning
>> burn rate is not a constant, among other things it depends on
>> pressure and temperature, both of which change as a piston moves
>> and also as a function of how much burning has already happened
>>
>> -- 
>> - Daniel
>> Fredericton, NB  Canada
>> _______________________________________________
>> Gasification mailing list
>>
>> to Send a Message to the list, use the email address
>> Gasification at bioenergylists.org
>>
>> to UNSUBSCRIBE or Change your List Settings use the web page
>> http://lists.bioenergylists.org/mailman/listinfo/
>> gasification_lists.bioenergylists.org
>>
>> for more Gasifiers,  News and Information see our web site:
>> http://gasifiers.bioenergylists.org/
>
>
>
>
> ------------------------------
>
> Message: 12
> Date: Fri, 25 Feb 2011 11:27:28 -0400
> From: <bayent at ns.sympatico.ca>
> To: Discussion of biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>,    "doug.williams"
>    <Doug.Williams at orcon.net.nz>
> Subject: Re: [Gasification] NZ Earthquake, OT
> Message-ID: <20110225102728.BS5UK.606307.root at tormtz01>
> Content-Type: text/plain; charset=utf-8
>
> Hi Doug,
>
> We are all watching this disaster unfold and wishing it had never 
> happened.
> Canada too will get it's day in this regard as our west coats is long past 
> due for a very big one.
> Where we are here is very stable supposedly but still quakes happen.
> Property damage is one thing and is very difficult but the lost lives and 
> trauma of loosing family is really rough.
> Glad you personally were not physically affected.
>
> Charles
>
>
>
> ------------------------------
>
> Message: 13
> Date: Thu, 24 Feb 2011 18:45:02 -0800
> From: Thomas Reed <tombreed2010 at gmail.com>
> To: Discussion of biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>, jim mason
>    <jim at allpowerlabs.org>, Tom Miles - Stoves - Oregon
>    <tmiles at trmiles.com>
> Cc: Discussion of biomass pyrolysis and gasification
>    <gasification at lists.bioenergylists.org>
> Subject: Re: [Gasification] ideal wood gas engine
> Message-ID: <08BADD45-1197-4A59-879F-3FBFF2D0F617 at gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Bill, Doug and all
>
> I have spent many days at the CGP and these authors work on producer gas 
> far exceeds anything we do in the US - Except maybe Brian Wilson's lab at 
> Fort Collins which will be running tests on the 10 kW gasifiers now being 
> sold by Jim Mason's shop.  I look forward to these results.
>
> Tom Reed
>
> Dr Thomas B Reed
> President, The Biomass Energy Foundation
> www.Woodgas.com
>
> On Feb 24, 2011, at 5:41 PM, "Bill Klein" 
> <Bill_Klein at 3iAlternativePower.com> wrote:
>
>> Greetings and a good day to each of you!
>>
>> As I read through the most recent postings about the "perfect engine" for 
>> our wood gas, I was reminded of a study done a few years ago. Those 
>> involved, the authors of the abstract below are quite respected in their 
>> field, while pioneering work that has contributed to many of the small 
>> successes in our industry.
>>
>> Though a bit lengthy, the abstract is quite revealing and may add 
>> something to the conversation. Respectfully, Bill Klein - 3i
>>
>>
>>
>> Biomass and Bioenergy 21 (2001) 61?72
>> Biomass derived producer gas as a reciprocating
>> engine fuel?an experimental analysis
>> G. Sridhar _, P.J. Paul, H.S. Mukunda
>> Combustion Gasification and Propulsion Laboratory,
>> Department of Aerospace Engineering,
>> Indian Institute of Science, Bangalore 560 012, India
>> Received 28 June 2000; accepted 13 December 2000
>> ABSTRACT
>> This paper uncovers some of the misconceptions associated with the usage 
>> of producer gas, a lower calorific gas as a reciprocating engine fuel. 
>> This paper particularly addresses the use of producer gas in 
>> reciprocating engines at high compression ratio (17 : 1), which hitherto 
>> had been restricted to lower compression ratio (up to 12 : 1). This 
>> restriction in compression ratio has been mainly attributed to the 
>> auto-ignition tendency of the fuel, which appears to be simply a matter 
>> of presumption rather than fact. The current work clearly indicates the 
>> breakdown of this compression ratio barrier and it is shown that the 
>> engine runs smoothly at compression ratio of 17: 1 without any tendency 
>> of auto-ignition. Experiments have been conducted on multi-cylinder spark 
>> ignition engine modified from a production diesel engine at varying 
>> compression ratios from 11:5: 1 to 17: 1 by retaining the combustion 
>> chamber design. As expected, working at a higher compression ratio turned 
>> out t
> o be more efficient and also yielded higher brake power. A maximum brake 
> power of 17:5 kWe was obtained at an overall efficiency of 21% at the 
> highest compression ratio. The maximum de-rating of power in gas mode was 
> 16% as compared to the normal diesel mode of operation at comparable 
> compression ratio, whereas, the overall efficiency declined by 32.5%. A 
> careful analysis of energy balance revealed excess energy loss to the 
> coolant due to the existing combustion chamber design. Addressing the 
> combustion chamber design for producer gas fuel should form a part of 
> future work in improving the overall efficiency. c_ 2001 Elsevier Science 
> Ltd. All rights reserved.
>> Keywords: Biomass; Compression ratio; De-rating; Producer gas; Spark 
>> ignition engine
>>
>> 1. Introduction
>> With the renewed interest in biomass energy by necessity, biomass-based 
>> technologies are achieving prominence not only as rural energy devices 
>> but also as industrial power plants. Gasification is one such process
>> ? Corresponding author. Tel.: +91-80-360-0536; fax: +91-80-3601692.
>> E-mail address: gsridhar at cgpl.iisc.ernet.in
>> (G. Sridhar).
>> where clean gas could be generated
>> using a wide variety of bio-residues as the
>> feed stock and in turn use the fuel gas for power generation purposes. 
>> These are being used in standard diesel engines in dual-fuel mode of 
>> operation so as to obtain diesel savings up to 85%. Operation of engines 
>> on gas alone has been explored in some limited sense by a number of 
>> researchers ever since World War II. In the
>> present times, adopting these technologies has immense economic benefits; 
>> a route pursued by a number of researchers is in [1?5].
>> Development of gas engines using producer gas has been explored ever 
>> since World War II. It is estimated that over seven million vehicles in 
>> Europe, Australia, South America and Pacific Islands were converted to 
>> run on producer gas during World War II. These engines were spark ignited 
>> engines, mostly in the lower compression ratio bracket operating either 
>> on charcoal or biomass derived gas. Extensive fieldwork has been carried 
>> at National Swedish Testing Institute of Agricultural Machinery [1] by 
>> mounting gas generator and engine set on trucks and tractors. There have 
>> also been sporadic installations at Paraguay and Sri Lanka [1] for power 
>> generation application.
>> The question of power generation using producer gas has been addressed in 
>> recent times by a few researchers [1, 2, 6] and attempts have been made 
>> to convert standard compression ignition engine to a gas engine with the 
>> relaxation imposed on the compression ratio (CR) and others [3] operating 
>> a supercharged SI engine to realize the rated output. Also, one 
>> researcher [4] has reported working on producer gas fuelled engine at 
>> high CR (16:5: 1) for water pumping application without any sign of 
>> knock. There appears no earlier work on a systematic study on the engine 
>> behavior using producer gas fuel. The other important reason that appears 
>> responsible is the non-availability
>> of standard and proven gasification systems, which could generate gas of 
>> consistent quality on a continuous basis for engine applications.
>> Systematic studies are essential from the viewpoint of establishing the 
>> highest useful compression ratio (HUCR) for producer gas fuel and also 
>> indirectly establish the octane rating for the fuel. This paper reports 
>> work on a producer gas fuelled spark ignition
>> engine converted from a production diesel engine.
>> A well researched, tested and an industrially proven gasifier system 
>> capable of generating consistent quality was employed as the gas 
>> generator for testing
>> purpose [7, 8]. The engine has been tested and verified at the highest 
>> compression ratio of 17: 1 in order to establish knock-less performance 
>> by capturing the pressure-crank angle trace. Subsequently the engine  has 
>> been tested at varying CRs so as to arrive at an optimum CR for maximum 
>> brake power and affiance. The overall energy balance has been analyzed 
>> and the shortcomings identified. Also the emission levels in terms of CO 
>> and NO have been examined.
>> 2. Misconceptions and clarification
>> Prior to this development there have been two misconceptions regarding 
>> producer gas fuel and they are identified as follows: (1) auto-ignition 
>> tendency at higher CR when used in reciprocating engine, (2) large 
>> de-rating in power due to calorific value of the fuel being low.
>> It was thought that these perceptions had no reasonable basis. Indeed, 
>> the basis for the contrary seemed to exist. Firstly, producer gas being a 
>> mixture of many gas species with large fraction being inert should have 
>> higher octane rating when compared to natural gas and biogas. The gas 
>> contains a large fraction of inert gases like CO2 and N2 accounting to 
>> 12?15% and 48?50%, respectively, and these could act as knock suppressors 
>> [9]. However, so far there has not been any research of octane rating 
>> test conducted on producer gas fuel. Moreover, it is not clear if any 
>> established test procedure exists for producer gas like the Methane 
>> number test for natural gas and biogas. One crude way of assessment is to 
>> test the fuel gas in standard engines and place them accordingly in the 
>> octane rating table.
>> Secondly, there is a general thinking that producer gas being a lower 
>> calorific fuel, the extent of de-rating would be large when compared to 
>> high calorific value fuels like natural gas (NG) and liquefied petroleum 
>> gas (LPG). The de-rating if any could be due to two possible reasons. 
>> Firstly, with the lower energy density fuels there is a net decrease in 
>> number of molecules when compared to high-energy fuels like diesel, 
>> gasoline, NG or LPG. This contributes to some de-rating in case of low 
>> energy density fuels [10]. De-rating of power on account of calorific 
>> value will be small because of marginal differences in the energy release 
>> per unit mixture (air+fuel gas) [11]. This can be explained as follows. 
>> The calorific value of producer gas varies between 4.7 and 5:0 MJ N m?3 
>> as against 30 MJ N m?3 for NG. The energy density per unit (producer gas 
>> +air) mixture is only 15?20% lower than NG and air mixture even though 
>> the calorific value of producer gas is one-eighth of NG. Thi
> s is because the stoichiometric air=fuel ratio for producer gas is 1.2 as 
> compared to 17 for NG. Hence the extent of de-rating with producer gas 
> would not be marginal compared to NG fuelled operation at comparable 
> operating conditions. This gap could be nullified by working producer gas
>> at higher CR when compared to NG. The upper limit of CR for NG has been 
>> identified to be around 15:8: 1 based on a recent work [10].
>>
>>
>>
>> 3. Earlier work
>> Shashikantha et al. [2] has reported related work on a converted diesel 
>> engine at CR of 11:5: 1. In addition to the change in CR, the combustion 
>> chamber of the original engine i.e. bowl-in piston (hemispherical)
>> was modified to Hesselman (shallow W) with an aim of achieving a higher 
>> level of turbulence by squish rather than swirl. With the above 
>> modification a power output of 16 kWe has been reported in gas
>> made with efficiency in the range of 21?24% against a rated output of 17 
>> kWe in diesel mode. However, the same authors [6] subsequently claim a 
>> lower output and efficiency of 11:2 kWe and 15%. These authors do discuss 
>> the knock tendencies at higher CR but no experimental evidence seems to 
>> be provided in support. Measurements have been reported of various 
>> parameters including that of exhaust emissions; however no measurements 
>> have been made with respect to gas composition, which is considered 
>> essential from the viewpoint of establishment of input energy.
>> The first experimental work in the higher CR range has been reported by 
>> Ramachandra [4] on a single cylinder diesel engine (16:5: 1 CR) coupled 
>> to a water pump. A power de-rating of 20% has been reported at an overall 
>> efficiency of 19% without any signs of detonation. This work does not 
>> report any other measurement like the pressure-crank angle diagram in 
>> order to rationalize some of the results. Work on gasoline engine 
>> operation on producer gas has been reported by Parke [12] with de-rating 
>> claims of 34%, compared to gasoline operation. The same authors [3] 
>> suggest supercharging to
>> enhance the engine output. Martin and Wauters [5] have reported work 
>> using charcoal gas and producer gas on an SI engine with a de-rating of 
>> 50% and 40%, respectively, at a CR of 7: 1. However, the same authors 
>> claim 20% de-rating when worked with producer gas at a CR of 11: 1. The 
>> authors present a CR barrier of 14: 1 and 11: 1 for charcoal and producer 
>> gas, respectively, with inadequate experimental justification. From the 
>> literature survey it appears that no experimental evidence is available 
>> to support the phenomenon of knock in producer gas engines, even though 
>> it is believed knock would occur at higher CR.
>> 4. Current investigations
>> It is a well-acknowledged fact that it is desirable to operate an 
>> internal combustion engine at the highest possible CR so as to attain 
>> higher overall efficiencies. But the gain in efficiency beyond a certain 
>> CR can  be expected to be marginal due to other influencing factors such 
>> as heat loss and friction. In the case of an SI engine the limitation of 
>> CR comes from the knock sensitivity of the fuel. It has been 
>> experimentally investigated that the upper limit for compression ratio 
>> for SI engine operation is 17: 1 beyond which there is a fall in 
>> efficiency [13]. The above conclusion
>> is based on extensive tests with iso-octane as the fuel also doped with 
>> anti-knock agent. If one were to consider this as the upper limit and 
>> since no other work has been conducted at higher CR for SI engines, 
>> choosing a production engine in the above range for the current 
>> investigation seemed very appropriate. The current investigation was 
>> conducted on a commercially available diesel engine so as to explore the 
>> possibility of working at the existing CR of 17: 1 and optimizing the 
>> same if required. At the onset of investigation, it was perceived that 
>> increase in CR could have conflicting effects on the power output of the 
>> engine. This could be explained as follows. It has been universally 
>> recognized that turbulent flame speed [9] plays a vital role in the heat 
>> release rate during the combustion process in an engine cylinder. The 
>> turbulent flame speed can be treated as an enhanced form of laminar flame 
>> under the influence of time varying turbulence [9] within the combustion
> chamber of the engine. The laminar flame speed is again a function of 
> initial pressure, temperature and the mixture composition. An earlier 
> computational work by Mishra [14] indicated that the laminar flame speed 
> for stoichiometric producer gas and air mixture could  decrease by 
> one-tenth as the initial pressure is enhanced by a factor of 40. However, 
> these calculations were made at an initial temperature of 300K, and the 
> initial temperature at which combustion starts is high in the case of 
> internal Combustion engines. The influence of initial pressure and 
> temperature on laminar flame speed can be explained in simple terms as 
> follows. The increase in the unburned gas temperature results in increase 
> in adiabatic flame temperature and hence the average reaction rates. The 
> increase in the reaction rate is a result of the increase in the number of 
> radicals released?thus contributing to increase in the flame speed, 
> whereas the rise in pressure can result in reduction in the amoun
> t of radicals released thus retarding the flame speed. Therefore, the 
> conflicting nature of the effects of initial pressure and temperature 
> needs to be recognized. The effect of these at varying CR is an additional 
> feature that needs to be recognized in order to arrive at the optimum CR. 
> Consequently, the present investigation was started with an assumption 
> that the optimum compression ratio would be between 12: 1 and 17: 1 for 
> maximum power output and overall efficiency.
>> In the current investigation, CR was the parameter that was varied. The 
>> influence of CR on power, efficiency and emissions has been studied in 
>> some detail. Minimum ignition advance for best torque (MBT) has been 
>> determined at different Rs. The variation of cylinder pressure with time 
>> has been captured using a piezo-based transducer. The overall energy 
>> balance has been projected.
>> 5. Conversion methodologies
>> A three cylinder, direct injection diesel engine of 3:3 l capacity, with 
>> a CR of 17: 1 was converted into a spark ignition engine to drive a 
>> 25-kVA alternator. The salient features of the engine are given in Table 
>> 1.
>> Modifications attempted on the engine for conversion are as follows:
>> 1. Insertion of spark plug in place of fuel injectors without changing 
>> its location (centrally located).
>> 2. Adaptation of a distributor type battery based ignition system with a 
>> provision to advance=retard ignition timing. The set ignition timing was 
>> checked using a stroboscope.
>> 3. The combustion chamber design comprising a flat cylinder head and 
>> bowl-in piston was retained. No attempts were made to change the 
>> combustion chamber design except that the thickness of the cylinder head 
>> gasket was varied to accomplish different CRs of 17 : 1, 14:5 : 1, 13:5 : 
>> 1 and 11:5 : 1.
>> 4. For in-cylinder pressure measurement, provision was made on one 
>> cylinder head by drilling a 1:5 mm diameter hole for pressure measurement 
>> and fitting an optical sensor on the crankshaft for crank angle 
>> measurement.
>> 6. Experimental set-up and measurement scheme
>> The well-researched, tested and industrial version of IISc?s-open top 
>> down draft, twin air entry 75 kg h?1 solid bio-residue gasifier system 
>> [7] formed the gas generator. This state-of-the art technology has 
>> undergone
>> extensive testing both in India [8] and overseas [15] and proven to be a 
>> world-class system. The system has qualified for long hours of continuous 
>> operation in meeting the industrial requirements in terms of generation 
>> of consistent quality gas. The overall details of the gasifier system are 
>> presented in Fig. 1. As shown in the figure, the system had the provision 
>> to test the quality of the gas prior to supply to
>> engine. At the engine intake, a carburetor is provided
>> the engine. At the engine intake, a carburetor is provided for 
>> proportioning air and fuel flow. As there were no carburetors 
>> commercially available to cater to producer gas, a locally made 
>> carburetion system and manually controlled valve were used for 
>> proportioning.
>> Measurements were made with respect to the following parameters:
>> (A) Producer gas compositions using on-line gas analyzers. The gases 
>> analyzed were CO, CO2,  CH4, O2 and H2. The N2 concentration was deduced 
>> by difference. The CO, CO2, CH4 components were determined using infrared 
>> gas analyzers and the H2 component using a thermal conductivity-based 
>> analyzer. The O2 measurement system was based on chemical cell.
>> (B) In-cylinder pressure variation data synchronized with the crank angle 
>> measurement was acquired
>> on a computer for every one-degree crank angle.
>> The pressure measurement was accomplished using
>> a pre-calibrated Piezo based pressure transducer
>> (M=s PCB make).
>> (C) Measurement of voltage and current across
>> three phases and frequency for power output
>> calculations?the load bank constituted of resistors.
>> (D) Air and gas Kow to the engine using pre-calibrated
>> venturimeters.
>> (E) Engine exhaust analysis?O2, CO2; CO, and NO
>> and temperature.
>> with the crank angle measurement was acquired
>> on a computer for every one-degree crank
>> on a computer for every one-degree crank angle. The pressure measurement 
>> was accomplished using a pre-calibrated Piezo based pressure transducer 
>> (M=s PCB make).
>> (C) Measurement of voltage and current across three phases and frequency 
>> for power output calculations?the load bank constituted of resistors.
>> (D) Air and gas FLow to the engine using pre-calibrated venturimeters.
>> (E) Engine exhaust analysis?O2, CO2; CO,
>> and NO and temperature.
>> 7. Experimental procedure
>> Experiments were initiated on the engine only after the gasifier system 
>> stabilized i.e. attained steady state operation in terms of generation of 
>> consistent quality gas. The typical time scale for attaining steady state
>> of operation from the cold start was 2?3 h. During this period the gas 
>> was flared in a burner. The gas composition was determined using on-line 
>> gas analysers, pre-calibrated using a known producer gas mixture. The 
>> calibrations of these analyzers were checked at random time intervals so 
>> as to minimize errors in long duration operation. Typically gas 
>> composition at the time of start of the engine test was 19 ? 1% H2; 19?1% 
>> CO; 2% CH4; 12?1% CO2; 2?0:5% H2O and rest, N2. The mean calorific value 
>> of gas varied around 4:65?0:15 MJ N m?3.  The feedstock used for 
>> gasification is Causurina species wood with moisture content between 12% 
>> and 15% on dry basis (sun-dried wood).
>> Once the gas composition stabilized, the engine was operated for a few 
>> minutes at 1500 RPM at no-load condition. All the tests on the engine 
>> were conducted around a constant speed of 1500?50 RPM. The throttling for 
>> speed control and air and fuel proportioning was achieved using manually 
>> operated valves.
>> Experiments were conducted at CRs of 17: 1, 14:5: 1, 13:5: 1 and 11:5: 1 
>> and these CRs were  achieved by varying the thickness of the cylinder 
>> head gasket. The compression ratio values are based on the cylinder?s 
>> geometric measurements and were verified by matching the motoring curve 
>> with an engine simulation curve. The engine was tested at different 
>> ignition timing settings to determine the MBT at different CRs. With set 
>> ignition timing, the air and fuel were tuned to achieve maximum power. 
>> Measurements were initiated 10?15 min after attaining stable operation. 
>> The in-cylinder pressure data with a resolution of 1? crank angle was 
>> acquired on a computer in excess of 100?150 consecutive cycles. Prior to 
>> the start of these tests, the TDC was accurately determined using a dial 
>> gauge and synchronized with the optical crank angle measuring system with 
>> an accuracy of ?0:5?.
>> 8. Results and observations
>> 8.1. Performance
>> The first and the foremost result of these tests is that the engine 
>> worked smoothly without any sign of knock at a high CR of 17: 1. There 
>> was no sign of audible knock during the entire load range. Moreover, the 
>> absence of knock was clear from the pressure-crank angle recordings both 
>> at full load and part load.
>> The engine delivered a maximum output of
>> 17:5 kWe (20 kW shaft power) at a CR of 17: 1 with an overall efficiency 
>> of 21% compared to 21 kWe (24 kW shaft power) output at 31% efficiency in 
>> diesel mode. The overall efficiency calculated is based on the ratio of 
>> the shaft output delivered to the energy content in the biomass. The 
>> overall efficiency in gas mode is based on the ratio of mechanical shaft 
>> output to the energy content in the biomass. The useful output and 
>> efficiency decreased with the lowering of CR. A maximum output of 15:3 
>> kWe (17:6 kW shaft power) at an overall efficiency of 18% was obtained at 
>> a CR of 11:5: 1. The variation of brake power with CR is shown in Table 
>> 2. The power output at an intermediate CR of 14:5: 1 and 13:5: 1 were 
>> 16.4 and 16:2 kWe, respectively, and with overall efficiencies being 20%. 
>> The overall efficiency at 13.5 CR is the same as that at 14:5: 1 on 
>> account of leaner operation.
>> The extent of de-rating in brake power is about 16.7% at a CR of 17: 1 
>> and increased as high as 26% at 11:5: 1 when compared to diesel mode of 
>> operation. The gain in overall efficiencies from CR 11.5 to 17: 1 works 
>> out to be 16.6%, which means an increase of 3% per unit CR increment. 
>> However, the incremental gain per unit CR from 14.5 to 17: 1 is 2%. These 
>> figures are well within the range of 1 to 3% gains per unit incremental 
>> of CR [9]. The fuel?air equivalence ratio (PHI) at which the maximum 
>> power was derived was around 1.00?1.06 with the exception of 0.86 at CR 
>> of 13:5: 1. The air to fuel ratio is tuned from the viewpoint of deriving 
>> maximum output and therefore the efficiency figures are necessarily not 
>> the maximum that can be obtained. It may be possible to achieve higher 
>> overall efficiencies by operating at leaner conditions.
>> The peak shaft output at varying CR was found to be sensitive to the 
>> producer gas composition. The hydrogen fraction in the fuel gas dictated 
>> the ignition timing setting. Therefore the minimum advance for brake 
>> torque (MBT) varied with the change in hydrogen content in the fuel gas. 
>> A higher fraction of hydrogen means that the ignition timing has to be 
>> retarded in order to benefit from the increase in the flame speed. With a 
>> faster burn rate the optimum spark timing has to be closer to the TDC, 
>> the mixture temperature and pressure at the time of initiation of spark 
>> will be higher and hence the laminar flame speed at the start of 
>> combustion will also be higher. Therefore optimizing the ignition timing 
>> based on hydrogen fraction is vital from the viewpoint of deriving 
>> maximum shaft output.
>> Since the mixture flame speed is a strong function of hydrogen content in 
>> the gas, the MBT will differ based on the actual fuel gas composition. 
>> For a gas composition containing 20:5 ? 0:5% H2 and 19:5 ? 0:5% CO, the 
>> MBTs have been identified as shown in Table 2, the measurement accuracy 
>> of MBT is within 3? crank angle. The MBT in the present case has turned 
>> out to be about 6?10? BTDC at a CR of 17: 1 and has gone up to as high as 
>> 14?16? BTDC for a CR of 11:5: 1. These values are much lower compared to 
>> 30 to 40? BTDC at a CR of 11.5 based on earlier work [2, 6, 12] but 
>> matches with 10? BTDC [4] at a CR of 17: 1.
>> The mechanical efficiency of the engine at a CR of 17 : 1 is about 80% 
>> and increases to as high as 87% at a CR of 11:5 : 1. The increase in 
>> mechanical efficiency is attributed to the reduction in rubbing friction 
>> [16] due to lower cylinder pressures encountered at lower CRs. The 
>> mechanical efficiency values are based on indicated power measurement 
>> (based on integration of pressure?volume diagram) and these were found to 
>> be identical with the Morse test results.
>> 8.2. Pressure?crank angle data
>> The pressure?crank angle recording at all the CRs did not show any trace 
>> of knock for all ranges of load including that of peak load and this is 
>> visible from the pressure?crank angle diagrams as shown in Fig. 2. Faster 
>> burn rate due to presence of hydrogen in the fuel gas may be one factor 
>> for the non-knocking performance at higher compression ratio. The faster 
>> burn rate accompanied by retarded ignition timing setting obviates any 
>> auto-ignition tendency of the end gas. Increasing the flame speed or 
>> retarding the ignition timing setting is one possible way of reducing 
>> knock tendency and this is well acknowledged in the literature [9]. The 
>> maximum indicated mean effective pressure (IMEP) was obtained at ignition 
>> timing corresponding to the maximum shaft output. The IMEP obtained at 
>> varying CR as a function of ignition timing is shown in Fig. 3. The max 
>> IMEP recorded was 595 kPa at a CR of 17: 1 and declined to about 485 kPa 
>> at a CR of 11:5: 1. The maximum IMEP was obtained at
>  a PHI of 1.05 and this falls well within the anticipated PHI of 1.0 to 
> 1.1 [9]. The point of occurrence of peak pressure at all CRs occurred at 
> 18?19? ATDC, except that at 13:5: 1 which occurred at 17? ATDC, which is 
> close to the generally acknowledged value of 17?ATDC for MBT [9, 17]. 
> Therefore, for CR of 17: 1, 14.5 and 11:5: 1 the MBT should be more 
> advanced
>>
>> (lie within 2?3?) from what was actually measured. The variation of IMEP 
>> or the net useful output within this close range would be marginal. The 
>> peak cylinder pressures and their point of occurrence is shown in Table 
>> 3. The peak pressure at 14:5: 1 CR is lower than 13:5: 1 probably due to 
>> a slight departure from MBT. The coefficient of variation of the IMEP at 
>> all CRs and ignition settings occurred well within 3?3.5%, implying low 
>> cycle-to-cycle variation. The reason for low cyclic variation is the 
>> faster rate of combustion occurring inside the engine cylinder. The 
>> faster rate of combustion is attributed to higher flame speeds due to the 
>> presence of hydrogen in the gas and also to the bowl-in piston combustion 
>> chamber design with increased
>> squish effect.
>> 8.3. Energy balance
>> Fig. 4 represents the overall energy balance at a CR of 17: 1. The energy 
>> balance at MBT showed that about 32.5% of the energy was realized as 
>> useful output (indicated power); about 27% was lost through the exhaust 
>> (including the CO in the exhaust) and the remaining 40% to the cooling 
>> water (inclusive of radioactive losses, etc). As expected with the 
>> advancement of ignition timing, the loss through exhaust mode reduced and 
>> increased to the coolant route. The energy balance in gas mode showed 
>> that a large fraction of
>> the energy was lost to the cooling water when compared to the diesel 
>> mode. Fig. 5 compares the energy balance in gas and diesel mode (at rated 
>> output of 21 kWe) at a CR of 17 : 1, the energy loss at maximum power 
>> delivered to the coolant and miscellaneous is about 40% compared to 33% 
>> in diesel and whereas, the energy loss through exhaust in gas mode 
>> decreased by 5%. The indicated power and thereby the thermal efficiency 
>> being higher in diesel mode is evident from the pressure?time curve shown 
>> in Fig. 2. The energy balance
>> at varying CRs is shown in Fig. 6. There was an increase in the loss of 
>> energy through exhaust (which includes the energy in the form of CO) with 
>> the reduction in the CR, whereas, the loss through the coolant and 
>> miscellaneous was higher at higher CR. The useful energy is 32.5% at a CR 
>> of 17: 1 and has declined to 25.7% at a CR of 11:5: 1. The useful energy 
>> at a CR of 13:5: 1 has stood about the same as that at 14:5: 1 due to a 
>> relatively leaner operation. The increased amount of heat loss to the 
>> cooling water as a whole in gas operation
>> could be attributed to the engine combustion chamber design. It has been 
>> quoted in the literature [9] that with engine geometries such as 
>> bowl-in-piston there will be 10% higher heat transfer. The heat transfer 
>> to the coolant in the current case falls well within this range. With the 
>> increase in compression ratio the overall conversion efficiencies must 
>> improve thermodynamically, similarly, the heat loss to the coolant and 
>> exhaust should have reduced. However, increased energy loss to the 
>> coolant at a higher compression
>> ratio is probably due to increase in heat transfer coefficient.
>> accounted for because it forms a small part (_ 5%) of NOx generated [9]. 
>> The NO level has been represented in milligram per unit MJ of input 
>> energy. These results have been compared to the Swiss norms because of 
>> some earlier collaborative work with the
>> Swiss scientists; it was indicated that Swiss norms were stringent with 
>> respect to the emission levels. The NO level reduced with the retardation 
>> of ignition timing and this feature was observed for all CRs. The
>> NO level was observed to be maximum at the highest compression ratio with 
>> advanced ignition timings, whereas for the MBT range of 6?20? BTDC the NO 
>> was roughly about the same in almost all the cases. However, there was 
>> one exception of NO being higher at MBT for a CR of 13.5 due to a leaner 
>> operation.
>> It is a well-known fact that NO generation is strongly dependent on the 
>> temperature and also residence time in the combustion chamber. With the 
>> flame speed of the gas mixture being high, the ignition setting is 
>> retarded whereby the residence time in the high temperature combustion 
>> chamber is automatically reduced. Therefore, the low NO levels at 
>> retarded ignition setting is an expected and consistent behavior. The 
>> above results match well with those quoted in the literature [9], which 
>> show small to modest variation of NO with CR. The variation of carbon 
>> monoxide (CO) with PHI is shown in Fig. 8. The CO levels have been 
>> represented in grams per MJ of input energy. The trend of CO with PHI is 
>> clear from the figure. The CO levels were lower at the highest CR, and 
>> this could be attributed to higher temperatures, leading to relatively 
>> complete combustion.
>> 9
>> Been smooth and it has been established beyond doubt that the operating 
>> engines using producer gas in SI mode at higher compression ratios is 
>> technically feasible. The cylinder pressure?crank angle trace has shown 
>> smooth pressure variations during the entire combustion process without 
>> any sign of abnormal pressure raise. A shorter duration of combustion has 
>> been observed with producer gas fuel, requiring
>> retardation of the ignition timing to achieve MBT. These faster burning 
>> cycles are corroborated by low cyclic pressure fluctuations with a 
>> coefficient of variation 3%. The faster burning process has been 
>> identified to be due to the higher flame speed of the fuel gas mixture 
>> and the same
>> h
>> content in the gas. So, increased quantity of hydrogen in the fuel gas 
>> mixture is desired from the viewpoint of approaching an ideal cycle 
>> operation. The perceived
>> negative influence of pressure on flame speed at higher CR does not seem 
>> to exist based on the above results. The maximum de-rating in power is 
>> observed to be 16% in gas mode when compared to diesel operation at 
>> comparable CR. The extent of de-rating was much lower when compared to 
>> any of the previous studies [3?6]. This number matches with a similar 
>> kind of de-rating reported with NG operation [10]. However, the overall 
>> efficiency drops down by almost 32.5% compared to normal diesel mode of 
>> operation. A careful analysis of the energy balance revealed excessive 
>> heat loss to the coolant at all CRs and this resulted in engine 
>> overheating within 30?40 min of operation at full load. This phenomenon 
>> of excessive heat loss could be attributed to bowl-in piston combustion 
>> chamber design. Higher heat loss to the cylinder walls can be expected 
>> because the combustion chamber is originally meant for diesel operation 
>> with inherent swirl. Hence suitable modification of the combustion ch
> amber is essential from the view point of reducing the energy loss to the 
> coolant. Reduction in 10% heat loss to the coolant would amount to 
> improvement in overall efficiencies by 3%. The study of the engine 
> combustion chamber and modifications can be looked upon as future work.
>> R
>> [1
>> mechanical wood products branch of FAO forestry paper No. 72, Food and 
>> Agriculture Organization of United Nations, Rome, 1986.
>> [2
>> GS, Kamat PP, Parikh PP. Development and performa
>> 15 kWe producer gas operated SI engine. Proceedings of Fourth National 
>> Meet on Biomass Gasification and Combustion, Mysore, India, vol. 4, 1993. 
>> p. 219?31.
>> [3
>> Biomass producer ga
>> Engines?naturally aspirated and supercharged engines. Michigan: American 
>> Society of Agricultural Engineers, 1981. p. 1?35.
>> [
>> Performance studies
>> engine. Proceedings of Fourth National Meet on Biomass Gasification and 
>> Combustion, Mysore, India, vol. 4, 1993. p. 213?8.
>> [5
>> Performance of charcoal
>> combustion engines. Proceedings of International Conference?New 
>> EnergConversion Technologies and their Commercialization?s, vol. 2, 1981. 
>> p24.
>> [6
>> Veerkar S. Design dev
>> spark ignited producer gas engine. Proceedings of the XIV National 
>> Conference on IC Engines and Combustion, Pune, India, 1995. p. 97?107.
>> [7
>> Open-top wood gasifiers, renewable
>> energy?sources for fuels and electricity. Washington, DC: Island Press, 
>> 1993.
>> [8
>> Shrinivasa U, Sharan H. Results of an Indo-Swi
>> qualification and testing of a 300-kW IISc?Dasag gasifier. Energy for 
>> sustainable development, vol. 4, November 1994. p. 46?9.
>> [9
>> Internal combustion e
>> International edition. New York: McGraw-
>> Hill, 1989.
>> [1
>> Development of a natural
>> engine for optimum performance. Proceedings of institution of mechanical 
>> engineers, Part D, vol. 211, 1997. p. 361?78.
>> [1
>> Fuels from biomass and their rational utilization in internal combustion 
>> engines.
>> Proceedings of International Conference?New Energy Conversion 
>> Technologies and their Commercialization?s, vol. 2, 1981. p. 1334?40.
>> [12] Parke PP, Stanley SJ, Walawnder W. Biomass producer gas fuelling of 
>> internal combustion engines. Energy from Biomass
>> and Wastes V, Lake Buena Vista Florida. p. 499?516.
>> [13] Caris DF, Nelson EE.
>> A new look at high compression engines. SAE Transactions 1959; 67:112?23.
>> [14] Mishra DP, Paul PJ, Mukunda HS. Computational studies on the flame 
>> propagation in producer gas?air mixture and experimental comparisons, 
>> Proceedings of the XIII National Conference on IC Engines and Combustion, 
>> Bangalore, India,
>> 1994. p. 256?62.
>> [15] Giordano P.
>> Experience on running a wood based cogeneration power plant with the 
>> IISc?Dasag gasifier. Biomass Users Network (BUN-India), vol. 3(2), 
>> October 1999. p. 2.
>> [16] Gish RE, McCullough JD, RetzloD JB, Mueller HT.
>> Determination of true engine friction. SAE Transactions 1958; 66:649?67.
>> [17] Wu CM, Roberts CE, Matthews RD, Hall MJ.
>> Effects of engine speed on combustion in SI engines: Comparison of 
>> predictions of a fractal burning model with experimental data, SAE Trans. 
>> 1993; p. 2277?91.
>>
>> ----- Original Message -----
>> From: doug.williams
>> To: Discussion of biomass pyrolysis and gasification
>> Sent: Thursday, February 24, 2011 7:46 PM
>> Subject: Re: [Gasification] ideal wood gas engine
>>
>> Hi Tony and Colleagues
>>
>> > This may be my first post to this site, I trust you will all not hope 
>> > it is my last.
>>
>> As a fellow New Zealander, lets hear more from you, we cover a lot of 
>> engine "stuff", and new voices are most welcome.
>>
>> > Getting the Air/fuel ratio correct is also vital.  Using a "colortune" 
>> > sparkplug is the best way to really know when you have the correct 
>> > mixture as you can see the flame color within the combustion chamber.
>>
>> Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it to 
>> teach how exhaust temperatures and engine sound changed across gas/air 
>> mixtures, using a single cylinder Iron Horse engine. I sent both Kevin 
>> and Arnt a copy of the colour guide out of our kit, seeing as they were 
>> interested in this subject.
>>
>> > A turbocharger can be used to increase the volume of mixture which is 
>> > drawn into engine but whether or not they are practical given the 
>> > possibility of contaminated gas is something I    cannot comment on.
>>
>> This is a problem for producer gas in most DIY systems. We do better at 
>> the commercial level with more sophisticated filtration systems, but it 
>> is better to use naturally aspirated engines of larger cylinder capacity 
>> of lower RPM, than undersized turbocharged engines relying on high RPM 
>> for DIY projects.
>>
>> > The Mean effective pressure within the engine during the combustion 
>> > stroke, is largely dependent on the length of stroke of the engine, the 
>> > compression ratio and the ignition timing.
>> > The stroke cannot easily be altered but the compression ratio can be 
>> > changed on some engines by machining the cylinder head.
>>
>> Generally speaking, this would mainly be applied to very old engines, 
>> probably pre-dating around 1949. The literature records a lot of work in 
>> this area of compression ratios by Woods in the late 1930's early 40's 
>> (from memory), where it was established that around 11:1 was the optimum 
>> for producer gas. At this point, the extra friction from compressive 
>> forces consumed the "extra energy", and little was gained from higher 
>> compression.
>>
>> > If a petrol (spark ignited) engine is run on wood gas or any other gas, 
>> > the Ignition timing has to be altered.  In general the ignition timing 
>> > will be advanced by several degrees, in order to ensure as high a mean 
>> > pressure as possible is reached during the combustion stroke.
>>
>> This is true, but remember that WW2 petrol was of lower octane, and 
>> required ignition advancement. Modern engines have that advancement 
>> already built in for the higher octane available today. Then, separate 
>> charcoal gasifiers away from wood gasifiers, because the H2 content again 
>> changes ignition behaviour. Most engines set up to operate on LPG or 
>> natural gas, are from 10-12:1 compression ratio (of the smaller sizes), 
>> and run without alteration on 110-120 octane producer gas perfectly. 
>> Having said that, you can always tweak them if the situation demands that 
>> degree of perfection. The engine is the least of your worries if the gas 
>> making is unstable (:-)
>>
>> > The benefit of using a computer controlled ignition system is that most 
>> > if not all computer controlled systems have a "knock" sensor.  The 
>> > purpose of this device is to sense when the ignition of the fuel has 
>> > caused the pressure within the cylinder to rise so high that the 
>> > remaining un burnt fuel spontaneously explodes.  This results in engine 
>> > knock, the resulting noise is commonly known as "pinking"   Diesel 
>> > engines knock a lot of the time because the very design of the engine 
>> > is to raise the fuel temperature to point when it spontaneously burns.
>>
>> Speaking "generally", producer gas has no problem in most standard spark 
>> ignition engines, as the spontaneous ignition temperature for producer 
>> gas in our experience, is around 600C. You find these compression 
>> temperatures in diesels around 16:1 ratio, and again from experience, 
>> once you go over 17:1, the spontaneous ignition temperature makes the 
>> engine very unstable. We worked with Lister (NZ)  to develop dual fuel 
>> conversion kits for the Pacific region, converted to gas Ford diesels in 
>> the UK, Ford natural gas engines in USA, and purpose built gas engines in 
>> Germany.
>>
>> In all cases, the operating temperatures around the engine can affect the 
>> behaviour of the ignition temperatures, as will the actual CO,H2, and CH4 
>> content. Any uncracked hydrocarbons will also affect the timing 
>> behaviour, so be careful how you tinker with the timing. Nothing is 
>> written in stone!
>>
>> > Older engines that use a Distributor lack the anti-knock feature. 
>> > Commonly distributors have a simple mechanical advise mechanism, to 
>> > advance the ignition as the engine revs faster, and a >Vacuum Retard 
>> > mechanism which aids acceleration.  Engines which are subject to 
>> > varying loads, can benefit from the retard mechanism if there is any 
>> > kind of control valve /butterfly on the >intake, which would alter the 
>> > manifold vacuum.
>>
>> My genset engine is a  1949 Hillman engine, one of the early higher 
>> compression engines  (8:1) out of the UK. The vacuum advance and retard 
>> is disconnected, but we have not noticed any problems across a wide range 
>> of outputs for 1,000's of hours. It is a moot point however, and I will 
>> reconnect it next time I play to see if it makes any difference.
>> >
>> > Anyone setting the timing on an engine with a fixed load-speed, needs 
>> > to be sure the advance/retard mechanisms are either working correctly 
>> > or have been locked up. As fixed speed engines can "hunt" if there is 
>> > any faults in or if there is any small changes in the loading or fuel 
>> > supply.
>>
>> Gensets have to operate at fixed speed, so use a governor on the throttle 
>> butterfly, and as I said, our advance/retard control is disconnected, so 
>> cannot in any way affect how the engine hunts on load or gas changes. 
>> Producer gas has many surprises as an engine fuel, and we learn more by 
>> the day.
>>
>> Most of the above comments apply to fixed speed (RPM) applications used 
>> for electrical power generation, both base and variable loads, from our 
>> installation experiences 1978- 2010.
>>
>> Doug Williams,
>> Fluidyne Gasification.
>>
>>
>>
>>
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