[Stoves] Trying new burner for TLUD's

Paul Anderson psanders at ilstu.edu
Thu Aug 28 13:28:58 CDT 2014 

Dear Marc, Julien, and all Stovers,

There has been some good discussion (and hands-on work) about the 
combustor on the TLUDs.   Here are some miscellaneous comments.

1.  Marc wrote:
> (the paper says that the hole of the concentrator ring should be 70% 
> of combustion chamber diameter. In terms of area, it means about 50% 
> combustion chamber area)
I think that is mis-stated.   Most concentrators holes are about half of 
the diameter of the full ring (fuel chamber diameter). For 6 inch 
diameter fuel chambers, the size most used for holes is 3 inch diameter 
(plus or minus half inch is fine).    That hole is only 25% of the area 
of the whole disk.   Dean Still (at Stove Camp) said that his is with a 
4" dia chamber has a 2" hole (if I remember correctly).

2. Marc also wrote:
> I never liked (for cooking purposes) the single-thick flame that comes 
> out of the concentrator ring that use most of the TLUD's designs, 
> because you get a narrow over-heated spot in the bottom of the cooking 
> pot, and in a result of that, you don't get a good heat distribution 
> in the pot.
>
> I made a new "diffuser" burner, which gives a circular flame area, 
> instead of a single one.
>
> http://youtu.be/mhl6tt2A4T0
>
>
> Anyone knows any other works on this aspect?

The use of an annulus (ring) of gases for combustion (vs. the central 
flame of concentrators) was in the very first item ever written about 
what is now known as TLUD stoves.   See:

http://www.drtlud.com/wp-content/uploads/2013/12/woodgas-stove-reed-larson-1996.pdf

And that stove has difficulties with maintaining flame around the entire 
annulus  when the supply of gases is not high.   What I think I have 
been reading by the recent researchers is to have something like a 
concentrator and then an annulus, ALL below the pot.   I hope that can 
help solve the issues.

Paul

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 8/25/2014 2:04 AM, Marquitusus wrote:
> Hi Julien,
>
> Thank you for the info. and the paper.
>
> Yesterday I was applying all this information to my new burner design. 
> I realized that, according to this paper, the holes should be bigger 
> if I wanted not to reduce the draft. I assumed my new burner act as 
> the typical "concentrator ring", and make its empty area to be the 
> same size as the paper recommends (the paper says that the hole of the 
> concentrator ring should be 70% of combustion chamber diameter. In 
> terms of area, it means about 50% combustion chamber area)
>
> What I can say since now, regarding the firsts test with this new 
> burner, is that apart from the distribution effect, it mantains the 
> mixing effect (pyrogas+secondary air) of the classical concentrator 
> ring. I have observed that the flames coming out of the secondary air 
> entrance holes, tend to concentrate in the center of the burner, just 
> in the bottom of the area wich is not open. Then they make a spin 
> movement, and finally find its way through the empy areas.
>
> I suppose this movements in the bottom part of the burner, very near 
> the base of the flames, contribute to the mixing process. But, as you 
> say, I haven't tried it under difficult conditions, so I cannot say it 
> would be desirable in all conditions.
>
> Following your thoughts, I also think we should have to find the 
> optimal distance between the ring and the secondary air intake. In 
> this sense, I think that it should be desirable to mantain this 
> distance as short as possible, in order to not losing heat through the 
> sides. If we put a long mixing/expanding tube (chimney), we will have 
> a very large emitting heat area. If we find there is no alternative, 
> then we'll have to think about insulating all this area. That is the 
> reason why I try to mantain chimneys as short as possible. What do you 
> think about it?
>
> All the best,
> Marc
>
>
>
> ------------------------------------------------------------------------
> Date: Sun, 24 Aug 2014 09:56:59 -0400
> From: winter.julien at gmail.com
> To: stoves at lists.bioenergylists.org
> Subject: [Stoves] Trying new burner for TLUD's
>
> Hi Marquitusus;
>
> Your burner looks like an interesting idea.   It is worth checking to 
> see if it will operate under difficult conditions, such as low pyrogas 
> production from fuel > 12% (wet wt.) moisture.
>
> I have been testing various options such as annular rings for pyrogas, 
> concentrator disks (not rings cf. Anderson and Wendelbo), and swirls.  
> The problems with burners emerge with the fuel I described above.  
> What I find is that (1) objects over the top of the TLUD reactor that 
> prevent secondary air descending toward the fuel bed, and (2) swirls 
> generated near the base of the gas flame, don't work well under 
> difficult TLUD operating conditions.  I am going to post the results 
> of experiments on these shortly.
>
> The conclusion I have reached (for the burners I have tested) is that 
> it is best not to interfere too much with the bottom of the gas flame.
>
> However, once the gas fame is well established, modifying it higher up 
> in the burner to create turbulence or spread the flame could be a good 
> idea. Therefore, I think your idea has merit.   If you haven't already 
> done so, you may want to experiment with the distance your disk is 
> above the secondary air intake, i.e. is there sufficient space for the 
> gas flame to expand.
>
>
> Based on the work by
>
> 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).
> http://www.ewb.org.au/jhe/index.php/jhe/article/view/11
>
> you should check to see that the size of your disk, relative to 
> the burner outer diameter, doesn't slow down the TLUD reaction too much.
>
>
> All the best,
> Julien.
>
> -- 
> Julien Winter
> Cobourg, ON, CANADA
>
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