[Stoves] thoughts around ELFD Sampada / Venturi-burners / sooth

Thu Mar 31 23:15:59 CDT 2016

Dear Crispin,
considering the relative humidity of the air that is drawn into the
stove, the amount of steam that is used for pushing additional air
into the flame is negligible. Some energy of the burning wood is no
doubt being used for generating the steam, but one saves the
electrical energy which is normally used for operating the blower in
the conventional forced draft stoves.
Yours
A.D.Karve

On 3/31/16, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> Ethanol in solution might have two positive effects:
>
> Earlier 'thrust'
> Better combustion
>
> Spraying water into a flame holds no thermodynamic advantage unless it is
> produce from truly wasted heat or if it catalyses ‎some reaction. It can
> have the mixing we are speculating is the 'gain' but it will have to come at
> a small cost in terms of heat.
>
> There is a species of wood in Swaziland that ‎when burned, adds no heat to
> the fire on a net basis because it's moisture content is so high. Think of
> the steam being like that. Unless it is assisting the completeness of the
> burn, the steam isn't adding anything.
>
> I agree it could increase the burn rate but that isn't a thermodynamic gain.
> It may be that adding a small amount of ethanol or methanol will give a
> positive return for reasons we don't fully understand yet. Try it and
> calculate. Maybe it will have some water gas effect low in the fuel bed that
> improves the combustion efficiency higher up.
>
> Hydrogen is a wonderful igniter.
> Crispin
> ‎
> Dear Crispin,
> are you suggesting the use of ethanol because of its lower boiling point
> than water? I can imagine, that due to this property, the action of forcing
> air into the flame may start earlier than with water alone.
> Yours
> A.D.Karve
>
> ***
> Dr. A.D. Karve
>
> Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)
>
> Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
>
> On Wed, Mar 30, 2016 at 10:31 AM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com> wrote:
>
>> Martin you are inspiring me today.
>>
>> A.D. How about adding something to the water? If you put in a little
>> ethanol, which I know is very difficult to obtain in India, would it
>> affect
>> the quality of the combustion?
>>
>> I know that an ethanol evaporator is possible and it may be that 2 or 5%
>> or 10% ethanol will have some unexpected and beneficial effect on the
>> flame. If all the vapour ends up in the flame there is nothing to lose in
>> terms of fuel waste.
>>
>> Co-firing often produces a much cleaner result than at least one of the
>> fuels alone.
>>
>> Regards from the DUE Conference
>> Crispin
>>
>>
>> Dear Anand and stovers,
>>
>> it is great and I am happy, that the  ELFD-Sampada stove, invented by
>> your
>> daughter, Dr. Priyadarshini Karve, works excellent.
>>
>>  I want to invite the stovers, to see and get aware, a general system in
>> this stove.
>>
>> All burners with forced draft are somehow "venturi-burners".
>>  Air-jets shooting into a gas-atmosphere suck gas into that air-jet.
>> In the TLUDs it is inverted to normal venturi gas-burners, and that is an
>> excellent idea, because woodgas is not really pure gas.
>> It tends to clog nozzles by tars.
>>
>> Now look to the ELFD-Sampada stove as a "double"-venturi burner-system.
>> 1. vapor-jet drives air, in order to make
>> 2. air-jets, which blow into woodgas, and each jet forms by that  a
>> "somehow"-venturi-burner, as in a forced-draft TLUD.
>>
>> Let me return to the simple gas-venturi-burners to guess about needed
>> pressures:
>>
>> LPG burners have a gas-pressure about 30 to 50 mbar; natural gas burners
>> even lower ( 20 to 25 mbar?)
>> Rough assumed ( I am aware: big ratio-differences are possible): The
>> streaming gas through the nozzle sucks about the same volume of air, to
>> form together an excellent combustible mixture.
>> If so, that mixture could be made invers too: 30 to 50 mbar air-jet can
>> suck the needed volume of woodgas.
>> And to get an  air-pressure about 30 to 50 millibar:
>> - A venturi-system driven by steam, -thumb-calculated-; has steam,
>> pressurized to 100 mbar (or easily some lower or higher)
>>
>> - Let us assume, that the steam condenses to water,
>>  naturally except the amount of water that is still in gas-form under
>> that
>> conditions (below 100°C).
>>  If the temperature in the system is above 100°C, there will be a lot of
>> water(in gas-form) beside the air.
>> ( same thumb "beginning" assume 50/50 above 100°C ??)
>> - The ELFD-Sampada shows in reality that the containing water does not
>> disturb the combustion. In contrary it seems to help combustion in
>> combination with forced draft. - I did not hear of speaking there would
>> be
>> water dripping out of the stove.
>>
>> What about sooth and water?
>>
>> The former discussion in the stoves-list about sooth, made me looking for
>> sooth. I learned it is technically produced in different manners and in
>> different qualities, for lots of purposes. - Yes they really want tons of
>> sooth, we don't even want grams and want to avoid milligrams-
>> One solution to form sooth is to spray water into a flame.
>> Shouldn't we get to know, from industry by what amount  of water (and
>> temperature) sooth starts to form, that we can avoid that?
>> And in contrary: what amount of water(in gas-form) makes burn better??
>>
>> The lesson I learned:
>> As sooth is in parts like graphite, there are C's bound to C's, within a
>> layer forming 6-rings, and that ring is so strong, that it needs more
>> than
>> 1000°C to burn/destroy the C-C-bondages.
>> -That means, we have to avoid _from beginning!_ the forming of sooth so
>> strictly as possible, because it is so difficult to get it burnt.
>> - The simple truth I want to keep in my awareness:
>> Sooth is no charcoal-C and needs roughly double the temperature of
>> charcoal to burn!
>>
>> Just some of my ideas from before and after learning about the
>> ELFD-Sampada-stove-
>>
>> Kind Regards to all,
>> - and my compliments to Dr. Priyadarshini Karve.
>>
>> Martin
>>
>>
>>
>>
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>

-- 
***
Dr. A.D. Karve

Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)

Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)