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Dear Roberto</div>
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I think this can happen at low power with the pot on if there is secondary air entering some distance above the fuel, say 40 mm. You can often see it with a TLUD, no pot and low power. </div>
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Keep having fun!</div>
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Crispin </div>
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<div dir="ltr">Thanks Crispin for the answer.
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<div>I don't know if with a spot on top of it, occurs the phenomenom.</div>
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<div>I only see this with low power, and the strange thing is that the stove have a chimney. So is hard to me to believe that cool air are entering from the chimney.</div>
<div> Looking the video with more attention, y could see some sparks coming out from the edges of the central hole (at 23 seconds aprox.). This confirm, for me, that the flame path form a toroidal flow.</div>
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<div>I concur that the toroidal flow are possibly formed with some primary air rising along the wall of the chamber (vertical flow), that combined with the secondary air (horizontal flow), form the donut or toroidal flow. Then, the combustion gases flow to
the chimney through the edge or perimeter of the combustion chamber.</div>
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<div class="x_gmail_signature">Greetings<br>
Roberto</div>
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<div class="x_gmail_signature"><b style="color:rgb(0,0,0); font-family:'Times New Roman'; font-size:medium">Crispin Pemberton-Pigott</b><span style="color:rgb(0,0,0); font-family:'Times New Roman'; font-size:medium"> </span><a href="mailto:stoves%40lists.bioenergylists.org?Subject=Re%3A%20%5BStoves%5D%20Flame%20center%20go%20down%20into%20the%20combustion%20chamber&In-Reply-To=%3CCOL401-EAS220933B51DFCC0353E3772BB1BE0%40phx.gbl%3E" title="[Stoves] Flame center go down into the combustion chamber" style="font-family:'Times New Roman'; font-size:medium">crispinpigott
at outlook.com </a><br style="color:rgb(0,0,0); font-family:'Times New Roman'; font-size:medium">
<i style="color:rgb(0,0,0); font-family:'Times New Roman'; font-size:medium">Fri Mar 4 10:13:46 MST 2016</i><span style="color:rgb(0,0,0); font-family:'Times New Roman'; font-size:medium"></span>
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<pre style="white-space:pre-wrap; color:rgb(0,0,0)">Dear Roberto
Did this flame pattern occur only when you were not cooking – meaning looking at it through an open top? If so, it is quite possible the effect was caused by it entering the fire from above the stove.
If there was a pot in place and you observed the flame descending in the centre, it is most likely caused by air entering the periphery of the combustion chamber and rising immediately. This sets up a toroidal flow like a donut rolling around its circular centre line. It can be created by having primary air jets below the fuel, or just air rising along the wall of the chamber.
My observations are that it happens at low power, usually, when the generated gas volume is low. It is often seen when the pot is off and the air enters from above. It follows the descending flame in the centre and feeds the fire around the edge.
Regards
Crispin</pre>
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