[Stoves] Trying new burner for TLUD's

Fri Aug 29 11:51:52 CDT 2014

Dear Paul and others,

Thanks for your comments.

If you think the 0.7 diameter hole is not correct, what about the other conclusions of this paper? for example, it says that "the optimal chimney height is seen to be at 1,5D and a with of D" (D = diameter of the burning chamber)

Marc

Date: Fri, 29 Aug 2014 10:00:21 +0800
From: crispinpigott at outlook.com
To: stoves at lists.bioenergylists.org
Subject: Re: [Stoves] Trying new burner for TLUD's

"Anyone knows any other works on this aspect"

(circle of flame)

Dear Paul

‎I think that is exactly what Gus was doing. We had a discussion about it a couple of months ago. 

Regards 

Crispin testing cooking stoves with short chimneys - will report...

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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