[Stoves] My current project - very unfinished

Tue Apr 8 23:32:01 CDT 2014

Julien, list,  etal

	1.  Thanks for the reminder on the Birzer etal article.  I missed it in December.  This shows there can be a lot of help from University class projects.  The faculty advisor/teacher should get a lot credit for bringing this to the point of a published article.  We need more hard data like this.

	2.  My first reaction is that we should see more TLUDs controlling power output using a moveable (sliding?, rotating?) baffle or baffles.  Could be either above or below the secondary air ports, I should think.  The main point is to change the flow resistance - and one can do that either before or after the primary air enters the fuel supply.  Below is easy enough - but there could be a benefit in increased turbulence with the added flow resistance in the hottest part of the flame.  Thoughts?  (I just sent note to Mr. Anh about similarly controlling power output with metal screens.  I haven’t seen anyone doing either approach to power control.)

	3.  All the emphasis on changing flow in this paper is on increasing or decreasing flow through chimney heights and diameters.  I will look into this further using their data , but there is another reason that TLUDs (and not rockets or home gas burners) have any draft.  That is because when either H2 or CO (but not methane) are combusted, there is a pressure drop because there are fewer particles after combustion than before.  That is:   2*H2+O2 goes to 2 * H2O  and 2 * CO + O2  goes to 2 * CO2 .  In both cases 3 particles go to 2.  But CH4 + 2*O2 goes to CO2 + 2 H2O, with three particles on each side of the equation.   I have hope that the article's measured data will allow me to figure out how big an effect this is.    The combustion of pure hydrogen can give amazing (and useful) pressure differences, especially when the steam is condensed.  But here we have a lot of nitrogen and excess secondary air - making it difficult to know how big the pressure difference effect is when comparing to the chimney and barrier effects.

Ron	

On Apr 7, 2014, at 7:41 AM, Julien Winter <winter.julien at gmail.com> wrote:

> Hi Anh and all;
> 
> When making modifications to the air flow around the syngas fire, I am always wondering what I might be doing to the heat flow to the pot.  Clearly it is largely convective, and the flow of exhaust gas and its temperature will be important.  So when we tinker with air flow, I have in the back of my mind this recent open-source article:
> 
> Birzer, C; Medwell, P; Wilkey, J; West, T; Higgins, M; MacFarlane, G; Read, M.  2013.  An analysis of combustion from a top-lit up-draft (TLUD) cookstove.  Journal of Humanitarian Engineering, 2(1) 
> 
> This article doesn't discuss any gas burners, but deals with how the geometry of the chimney above the syngas fire affects TLUD energy output.  If the chimney or concentrator disk is too small, it causes too much resistance to air flow and lowers the heat output.
> 
> (This article was posted on "Stoves" in December, 2013  http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/2013-December/007778.html).
> 
> Cheers,
> Julien.
> 
> 
> On Mon, Apr 7, 2014 at 5:40 AM, Anh <ntanh at greengenvn.com> wrote:
> Dear Jock and Julien,
> 
>  
> 
> As per my observation with pellets, as pellets are small size, the space between them is small and it limit the PA from coming up to pyrolysis zone, even fully open PA may not be enough. Towards the end, when there is less pellets left, more PA will come up and may need to reduce it a bit.
> 
>  
> 
> I tried another way similar to with Julien did. I placed a metal net on top of the cap (concentration cap), it keep the flame lower, less soot and the net glowing red look quite nice. But it have some problem too, at some early time, it may reduce the airflow too much and not enough PA get in so I can only put on when the fire is stable.
> 
>  
> 
> Anh
> 
>  
> 
>  
> 
>  
> 
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Jock Gill
> Sent: Monday, April 07, 2014 7:47 AM
> To: Julien Winter
> Cc: revjcsd at juno.com; Discussion of biomass cooking stoves
> Subject: Re: [Stoves] My current project - very unfinished
> 
>  
> 
> Julien,
> 
>  
> 
> Glad you like the looks of Trash Can School of Pyro-Grilling ;-)
> 
>  
> 
> I do not have any instrumentation.  I can tell you, however, that I have not problem with the pyrolysis front stalling once it gets going.  I have some thoughts on this initial phase problem. I will try starting the unit with no restrictions on access to primary air.  Then once things are HOT, I will restrict access for the rest of the burn.  I will report back on this.
> 
>  
> 
> The oxygen supply may be a problem vis the secondary air:  not enough to get good clean combustion.  It might be good to raise the top of the draft can above the top of the outer can to avoid any combustion gases being sucked back down into the system?  I will also try this tomorrow.  Thanks for the tip!
> 
>  
> 
> Cheers,
> 
>  
> 
> Jock
> 
>  
> 
> Jock Gill
> 
> P.O. Box 3
> 
> Peacham,  VT 05862
> 
>  
> 
> Cell: (617) 449-8111
> 
>  
> 
> google.com/+JockGill
> 
>  
> 
> :> Extract CO2 from the atmosphere! <:
> 
>  
> 
> Via iPad
> 
> 
> On Apr 6, 2014, at 8:24 PM, Julien Winter <winter.julien at gmail.com> wrote:
> 
> Hi Jock et al;
> 
>  
> 
> That is a nice rig you have in the garbage can, and I like the burner.
> 
>  
> 
> I once tried heating the primary air, from the sidewalls of a TLUD, and I found that it reduced the buoyance effect within the fuel bed.  As the reaction progressed and the TLUD became hotter, the flaming pyrolysis front stalled to a smolder.  Besides a lower temperature gradient within the fuel bed, there may also be a problem with oxygen supply, because the density of air decreases as it expands according to Charles’s gas law: V1/T1 = V2/T2
> 
>  
> 
> To me, it doesn't look like that will be a problem in your garbage can, because of its size relative to the stove, but it is something to think about.
> 
>  
> 
> In my last email to "Stoves" I almost included a picture of my Jack Russell Terrier guarding a TLUD.  She likes cat.
> 
>  
> 
> Cheers,
> 
> Julien
> 
>  
> 
>  
> 
>  
> 
> On Sun, Apr 6, 2014 at 6:09 PM, Jock Gill <jg45 at icloud.com> wrote:
> 
> Here is what I am working on. Still figuring things out.
> 
> <IMG_3155.JPG>
> 
> The idea is to use a large outer can, in this case a 20 gallon unit, to do some pre-heating, but not so much as to create a run away retort effect, capture some hot air for warming, a pseudo turn down effect, keep breezes out of the air system, contain the fire and charcoal for safety.  Cook on high heat over the "fire", slow cook or warm, on the hot air  around the edges.  The air there gets so hot you can not pick up a pot by its handle.
> 
>  
> 
> It would be possible to mount a removable grill a bit below the top of the outer can.
> 
>  
> 
> Above, I  have used a gas stove grate to support a pan over the fire in a unit made from two coffee cans -- about 6 inches in diameter.  More on the cans latter.
> 
>  
> 
> Note:  There are no holes in the outer can at all.  it is working by down drafting air for both the primary and secondary air ports.  The primary air is supplied by thirty eight 3/32 inch holes in three rings.  The secondary air is currently a single row of 3/8th inch holes about 1 cm above the bottom plate of the FXJ burner.  It is very clear that I need more secondary air in just the right place.
> 
>  
> 
> So far,  I can get flamelets, but also quite a bit of very soft soot.  There appears to be no creosote.
> 
>  
> 
> <image.jpeg>
> 
>  
> 
> I've cut the primary air supply gap way down.  Next I will try a second row of 3/8s inch secondary air holes.  This configuration is hard to start, but once it gets going, it really gets going.
> 
>  
> 
> A pyrolysis process with a 6 inch diameter produce an awful lot of gas.  I am finding it a challenge to achieve a favorable fuel to air ratio.  If I can find it, I am hoping the soot deposits will vanish, or at least become minimal.
> 
>  
> 
> More as it is.
> 
>  
> 
> Jock
> 
>  
> 
> Jock Gill
> 
>  
> 
>  
> 
> P.O. Box 3
> 
> Peacham,  VT 05862
> 
>  
> 
> Cell: (617) 449-8111
> 
>  
> 
> google.com/+JockGill
> 
>  
> 
> :> Extract CO2 from the atmosphere! <:
> 
>  
> 
> Via iPad
> 
> 
> 
> 
> --
> 
> Julien Winter
> Cobourg, ON, CANADA
> 
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> 
> 
> 
> 
> -- 
> Julien Winter
> Cobourg, ON, CANADA
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