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Dear Marc</div>
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You have a lot of secondary air entering the upper fire with the primary air. This is typical for that layout. </div>
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Being invisible does not mean there is no smoke. It just might be diluted by excess air. </div>
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A crossdraft stove might have a quarter of the secondary air you do. It depends on a lot of things. If you want to progress further you need a combustion analyser. You want to have an oxygen level in the exhaust (right at the edge or under the edge) of the
pot of under 10.5%. </div>
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There are still a couple of things you can try. Put a grate above the primary air to catch the charcoal and burn it. It will save fuel. Then, make an opening at the back of the stove to admit the air. </div>
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Regards </div>
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Crispin </div>
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BBM 'Crispin'</div>
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<div><b>From: </b>Marquitusus</div>
<div><b>Sent: </b>Friday, June 5, 2015 19:14</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>[Stoves] Lots of primary air</div>
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<div dir="ltr">Hi to all,
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<div>Running my rocket stove, which is under a low-mass mud oven (which allows to clearly see if I the stove produces smoke or not) I have always observed that the cleanest burning happens when the primary air is not obstructed by ashes or coals. Also in all
the rocket stoves I have seen, it is mantain the air entrance free from obstacles for them to burn clean. The more primary air, the less smoke.</div>
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<div>So I build a combustion chamber with a lot of space below the burning sticks, so it can have a lot of primary air, never obstructed by ashes or burning coals. I also put a longer combustion tube, about 50cm long, to give the gases enough space and time
to completely burn. I also put some secondary air holes about 10cm above the burning sticks: 16 holes about 1cm diameter each.</div>
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<div>The result is quite satisfactory: most of the time I have no smoke, and only in the begining and when I put too much fuel I have smoke until the tips are well ignited. With this cleaningness of combustion, I'm using it again to power my oven without the
fear of getting the food "blackened" due to smoke.</div>
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<div>I know this experience does not agree with the clean combustion "laws" about primary/secondary air ratios of 1/4 or less, but this has really worked for me. I've tried this configuration a lot of times in the lasts months, and I've always found that more
primary air, gives less smoke.</div>
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<div>What do you think about it?</div>
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<div><span style="font-size:12pt">Regards,</span></div>
<div><span style="font-size:12pt">Marc</span></div>
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