[Stoves] Trials on TLUD gas burners

[Paul Anderson]

Ron,

I agree that it is better to have some blockage of the central part of 
the riser/combustion area.  But in the burner called "rectangular" 
(which could also be called "annular with interruptions") Julien is 
forcing the combustible gases to the periphery but then lets the flaming 
gases be pushed back into the center.

My preference (subject to further experimentation) is for the ConcBelow  
to also have a buff body or other obstacle into the center of the rising 
gases, keeping them forced to the periphery where the secondary air is 
entering.   The advantage of ConcBelow is that IF pyrolysis is not 
uniform in the fuel chamber and is sending more gases up one side than 
the other sides, those gases should be required to go through a central 
concentrator hole. And then be spread out as uniformly as possible to 
all of the sides.

Historical note:   The original and famous Reed-Larson (1996) natural 
draft TLUD did not have any effort at concentration, and it can be 
faulted for having flames on one side without ability to propagate 
flames on the rest of the annual ring of rising gases. There is a "wick" 
(obstacle) in the riser.   In contrast, the major accomplishment of Paal 
Wendelbo was with the concentrator disk (or hole) in the early 1990s, 
which I independently also accomplished in 2005 with the Champion TLUD 
design.   Some of us did put buff bodies into the rising flames (I 
suspect Wendelbo did), but we were always with the basic configuration 
that Julien has called ConcAbove.

The only person that I recall as advocating what would be a form of 
ConcBelow is Crispin.   He has pestered me about it, and doing that 
research was on my list of things to do (but the list is far to long).   
I thank Julien for doing that task on his own.  It is highly interesting 
that the work of Julien Winter was not done in all those intervening years.

And also, Alexis Belonio was advocating in January 2014 at the Aprovecho 
Open House about some form of spreading the gases that need to reach the 
secondary air that is coming in from the sides.   Alexis affirms that we 
should be able to have a blue flame from woodgas.   It is all about 
mixing (especially pre-mixing if possible).

***** change of topic ***********

I comment on Ron's statement:
> By looking closely, counterintuitively, the flames seem attached  NOT 
> over the gas apertures, but rather between them.  I think this is true 
> in all cases but can't see the case C "attachment" points.  Except in 
> private dialogs with Paul O, I have not seen this stated before in 
> print  - and don't know if it should be encouraged or discouraged.
I think this has been considerably discussed or at least observed.   It 
relates to the phenomenon of the "inverted flame" in which the air 
enters a zone of combustible gases instead of the combustible gases 
entering a zone of air (which is the case of common gas burners on 
stoves.   In the TLUD gasifiers, the secondary air holes are 
sufficiently close together that the inverted flames are filling the 
space between the apertures of the incoming gas (which is actually air).

Paul A.

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 5/2/2014 7:44 PM, Ronal W. Larson wrote:
> Julien,  cc list:
>
> Nice report.  Thanks for sharing.
>
>  1.  My conclusion is that the best results were from what you call 
> the "rectangular hole design" - generally the right-most in your 
> figures.  I put the difference down to the fact that you are blocking 
> the central part of the combustion area, so the pyrolysis gases are 
> much closer to the secondary air supplies.  Call this A.
>
> Next best is what you called concentrator below  (the left one - which 
> has 16 air ports (presumably smaller??).  Call this B.  (Do you see 
> any preference for 16 over 8 secondary air ports?
>
> It seems very wrong to place concentrators above the secondary air 
> ports.  Call this C.
>
> 2.   In your Figure 3, this is B, C, A from left to right.  (OK?)  The 
> middle figure is the worst?
>
> My criterion is the set of photos in Figure 4, with very clean 
> combustion for A, next best for B, and bad for C.  In Figure 4, in the 
> top row, B is at the right, and th bottom row, you have C left and A 
> right.  I see A as better than the open chimney - but no videos or 
> photos of the open chimney in action.  Can you compare A and open further?
>
> 3.    In the still photo and the two videos, I perceive a phenomenon I 
> have seen before (with Paul Olivier's deign).   By looking closely, 
> counterintuitively, the flames seem attached  NOT over the gas 
> apertures, but rather between them.  I think this is true in all cases 
> but can't see the case C "attachment" points.  Except in private 
> dialogs with Paul O, I have not seen this stated before in print  - 
> and don't know if it should be encouraged or discouraged.   I believe 
> if your large outer air ports in A, were made narrower and longer in a 
> circumferential direction, there might be a more continuous flame, 
> through which little pyrolysis gas could pass without being combusted.
>
> My guess is that you now have considerable excess air, and so could 
> get better het transfer to the cook pot, with less secondary air aperture.
>
> 4.  In the design A, all the holes cut be cut so as to create a swirl 
> - which might give improved combustion - and allow a shorter chimney.
>
> 5.   You would have a more "salable" design if you could control 
> primary air.  A short piece (or two?) of electrical conduit (1/2 " ID, 
> 7/8'OD - or larger??) costs hardly anything and could be fitted with a 
> conical plug to control primary air.  It would have to penetrate the 
> vertical walls of both cans, but wouldn't have to have a really tight 
> fit - just a lot more control through the pipe rather than air 
> slipping around it.   This would replace your present multi-hole 
> bottom, and you would have to put in a different "holey" plate for the 
> pellets to rest on.  Of interest to all would be how large a TDR (turn 
> down ratio) you could achieve (run for 1.5 hours??)
>
> 6.  So lots of suggestions that need not be on your plate.  But I 
> think you are really on to something with A vs B or C. 
>  Congratulations for what you have already accomplished.
>
> Ron
>

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