<html><head></head><body dir="auto" data-blackberry-caret-color="#00a8df" style="background-color: rgb(255, 255, 255); line-height: initial;"><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Dear Lanny </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">I have a suggestion you can help with. We TLUD and sheet metal builders need an instructional video from you on how to take a rectangular sheet and turn it into a down-drafting preheater. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">I made an up-drafting cone and it worked well - that was on the Grasifier. But it is not as good as a correctly designed down-drafting cylinder. In general an open-topped cylinder will draft air in and out (like a stove without a pot on). It should be a 'chamber' with wind-proof entry holes adequate to supply the air, then a descending cavity not more than, perhaps, 10 to 12mm of space, then entries into the combustion area. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">I have already described how to make blurted holes for that injection to ensure that the secondary air reaches the centre of the gas stream. The same can be applied to the air entries of the preheating chamber in that the smaller and more efficient the holes are, the less affected by wind the system is. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">So, how to attach the preheater to the middle of the stove? How best to close the top and bottom to the (usually) cylindrical body?</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">How about if we have production tools at the level of a two-roller jenny? Press tools?</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The general shape and method of functioning of a multi-fuel burner is understood. Making it by hand can be a challenge. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Some of the guesswork can be removed. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Regards </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Crispin </div> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br name="BB10" caretmarkerset="INVALID" class="markedForCaretMarkerRemoval"></div> <div style="font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">BBM 2B567C3</div> <table width="100%" style="background-color:white;border-spacing:0px;"> <tbody><tr><td colspan="2" style="font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"> <div id="_persistentHeader" style="border-style: solid none none; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding: 3pt 0in 0in; font-family: Tahoma, 'BB Alpha Sans', 'Slate Pro'; font-size: 10pt;"> <div><b>From: </b>Crispin Pemberton-Pigott</div><div><b>Sent: </b>Tuesday, May 20, 2014 08:59</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></div></td></tr></tbody></table><div style="border-style: solid none none; border-top-color: rgb(186, 188, 209); border-top-width: 1pt; font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"></div><br><div id="_originalContent" style="">
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Howzit Lanny!</div>
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Yes, the idea is that if the internal chimney section of the stove (anything above the fuel bed in TLUD's) is hotter than the down-drafting section that is the secondary air preheater, it flows up and the secondary air flows down. The 'thickness' of the secondary
air channel matters - mustn't be too broad or cold air will pass in and out again. </div>
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The trick is to have the secondary air get less preheating when the power is turned down so it doesn't halt the secondary air feed. </div>
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The reason this works is in part because air has quite a lot of oxygen and the air pressure is what it is. </div>
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That means in the case of a side-fed stick burner, that there will always be too much air getting in if the draft is always upward - typically 6-800% excess air which is too much to burn cleanly. </div>
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At low power the EA will run to 2000 per cent easily in a side feed stove with an open architecture. </div>
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One simple way to limit it is to lower the pot and use it as a flow controller but it is only 'right' at one power setting. The down-drafting approach can be right across the power range. </div>
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Regards </div>
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Crispin </div>
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BBM 2B567C3</div>
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<div><b>From: </b>Lanny Henson</div>
<div><b>Sent: </b>Tuesday, May 20, 2014 08:48</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] Natural draft TLUD turn-down</div>
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Interesting, is this self regulating?</div>
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On May 15, 2014, at 9:39 PM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com">crispinpigott@outlook.com</a>> wrote:<br>
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<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">I can suggest one additional effect to try which is to put a shell around the outside that is closed to the body at the bottom and open at the top. This
is a down-drafting secondary air preheater. The height of the upper lip strongly affects the performance so you need to find where to put it. The effect of this is to create a negative draft on the secondary air supply that balances the heat inside in such
a way that you get the exact airflow level you want at different power levels.</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">Crispin</span></p>
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