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Dear Marc</div>
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If you don't get the secondary air flames to reach the centre there will be a vertical cylinder of high CO gases that will hit the pot in the centre, spread out, and are unlikely to burn to completion. </div>
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Reducing the height of the cylindrical region above the concentrator makes the CO region harder to eliminate. </div>
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Regards </div>
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Crispin </div>
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BBM 2B990AFA</div>
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<div><b>From: </b>Marquitusus</div>
<div><b>Sent: </b>Monday, August 25, 2014 15:06</div>
<div><b>To: </b>Discussion of biomass cooking stoves</div>
<div><b>Reply To: </b>Discussion of biomass cooking stoves</div>
<div><b>Subject: </b>Re: [Stoves] Trying new burner for TLUD's</div>
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<div dir="ltr">Hi Julien,
<div><br>
</div>
<div>Thank you for the info. and the paper.</div>
<div><br>
</div>
<div>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)</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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, <span style="font-size:12pt">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?</span></div>
<div><span style="font-size:12pt"><br>
</span></div>
<div>All the best,</div>
<div>Marc</div>
<div><br>
</div>
<div><br>
<br>
<div>
<hr id="x_stopSpelling">
Date: Sun, 24 Aug 2014 09:56:59 -0400<br>
From: winter.julien@gmail.com<br>
To: stoves@lists.bioenergylists.org<br>
Subject: [Stoves] Trying new burner for TLUD's<br>
<br>
<div dir="ltr">
<div>Hi Marquitusus;</div>
<div><br>
</div>
<div>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.
</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div><br>
</div>
<div>Based on the work by </div>
<div><br>
</div>
<div>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).
</div>
<div><a href="http://www.ewb.org.au/jhe/index.php/jhe/article/view/11" target="_blank">http://www.ewb.org.au/jhe/index.php/jhe/article/view/11</a></div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div><br>
</div>
<div>All the best,</div>
<div>Julien.<br clear="all">
<br>
-- <br>
</div>
<div dir="ltr">Julien Winter<br>
Cobourg, ON, CANADA<br>
</div>
</div>
<br>
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