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Dear Roberto</div>
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I agree with your analysis. There is a lot of merit in keeping the secondary flame in close proximity to the top of the fuel bed. The most important is that the secondary flame is harder to put out with a slight breeze (because it relights). The second is that
when the primary air is turned down to control the power, the secondary flame is able to remain hot enough to stay alight. Combined with external, down-drafting secondary air preheating (not like the Peko Pe) one can maintain the secondary air feed ration
under different primary air conditions. </div>
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Read and heed! TLUD's are not succeeding in meeting the turndown ratios required by ordinary cooking. To burn clean at different burn rates, whatever the fuel, you have to control both the primary and secondary air flows. </div>
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While a 'double controller' can work, turning the secondary air down at exactly the same time as the primary leads to a 2-3 minute period of very high PM and or CO and VOC's because of the retained heat in the fuel bed and stove body. This is worse if the combustion
chamber is ceramic or cast iron. </div>
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If the secondary air feed it an automatic, buoyancy-driven supply, it will draw in additional air as required during the cooling-off period. This explains the strange layout of the air supply in a Vesto Stove which tried to address the problems inherent in
David Hancock's (very advanced at the time) 1984 Tsotso Stove (which is still in production). </div>
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Regards </div>
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Crispin in Seoul enjoying spring </div>
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BBM 2B567C3</div>
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<div><b>From: </b>Roberto Poehlmann</div>
<div><b>Sent: </b>Tuesday, May 20, 2014 02:28</div>
<div><b>To: </b>stoves@lists.bioenergylists.org</div>
<div><b>Reply To: </b>Discussion of biomass cooking stoves</div>
<div><b>Subject: </b>Re: [Stoves] Natural draft TLUD turn-down</div>
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<div>Kirk,</div>
<div>this is a very interesting document, thanks to share it.</div>
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<div>The method 2 is like the 12 holes configuration of the Peko Pe design in page 9 of the following document:</div>
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<div><a href="http://www.adansonia-consulting.ch/document/Grass%20Cooker%20handbook_print.pdf?PHPSESSID=3d064accc3efbdafd3b1133a13129f9a">http://www.adansonia-consulting.ch/document/Grass%20Cooker%20handbook_print.pdf?PHPSESSID=3d064accc3efbdafd3b1133a13129f9a</a><br>
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<div>Maybe this is the reason that the Peko Pe stove don't need an internal chimney to operate. This 12 holes function also like 12 pilot flames, maintaining the secondary flame hot.</div>
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<div>I have replicated this design of the Peko Pe, and in operation, you can see the pilot flames attached to the 12 holes.</div>
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<div>Maybe the 4 holes concept in the middle of the combustion chamber can also helps to maintain a slow power consumption. When the pyrolysis front reach the middle of the combustion chamber, this "primary air" start to combust the charcoal, adding heat to
also support the flame.</div>
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<div>Roberto Poehlmann</div>
<div>Valdivia Chile.</div>
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<div>"</div>
<span style="font-family:arial,sans-serif; font-size:13px">All,</span><br style="font-family:arial,sans-serif; font-size:13px">
<br style="font-family:arial,sans-serif; font-size:13px">
<span style="font-family:arial,sans-serif; font-size:13px">Dr. Ron Larson, Dr. Paul Anderson and I have been working on the problem of lack of turn-down in natural draft TLUD cook stoves. We have found considerable success. Attached is a document introducing
the results of our labors. All information is in the public domain.</span><br style="font-family:arial,sans-serif; font-size:13px">
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<span style="font-family:arial,sans-serif; font-size:13px">K Harris</span><br style="font-family:arial,sans-serif; font-size:13px">
<span style="font-family:arial,sans-serif; font-size:13px">Santa Rosa, CA. USA</span><br style="font-family:arial,sans-serif; font-size:13px">
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