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Old 02-04-12, 08:47 AM   #8
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This is basically the same concept as the industrial heat recuperators that I worked with. One thing to watch out for with these small updraft gasifiers is the farther you place the secondary air ports away from the primary flame, the more chance there is for the secondary combustion to "flame out". It's not a big problem when it's running hot, but when adding fuel or when the fuel is running low, it might be more difficult to keep the secondary flame going. Remember that the secondary air absorbs heat from the hot primary gases. The longer the exchange between the two, the more cooling of the primary gases takes place. I think this is all part of "tuning" the design for optimal operation.

I had the idea that putting a displacer, like a closed pipe, inside the primary burn chamber starting just below the secondary air ports would force the gases around the outside of the chamber and promote more complete secondary combustion by reducing the amount of gas that can bypass the secondary air through the middle of the chimney.
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