posted 14 years ago
The flat plate is used to heat a kettle. I don't think it's a necessary part of the design.
Pre-heated air should help a lot. I think standard designs have the fuel intake & air intake as the exact same aperture, and accomplish re-burn just by more-thorough mixing, for simplicity's sake. It might get difficult to design well, if the primary burn were somehow choked down and an auxiliary air intake happened after that. Pre-heated air injected right at the site of combustion might blow the flame back through the fuel loading aperture, which would not be good.
The air currents are probably too strong for sawdust in standard designs. Maybe a wide (i.e., slow-flowing) chamber before the re-burn would allow that to work? I worry it might explode, also. Twigs, perhaps de-barked by goats, are the standard fuel. There's a continuous spectrum running from sawdust to shavings, chips, and twigs; I think coarse chips would be good, except for the effort needed to chip them.
A low-density refractory would be an excellent riser, in my opinion.
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