Re: Carbon content/two pot sunken stove

["Dean Still" <dstill@epud.net>]

Dear Crispin,

This is why I greatly appreciate this list, meaningful collaboration toward
progress! Thank you.

I agree that preheated primary air would possibly be very helpful to better
combustion in the Rocket stove. Let's chat about primary air first and then
in the natural course get to secondary air. I've tried to preheat primary
air for a while now. It is on my list of Unsolved Design Problems that I
hand out to students to gnaw on. The best that I've come up with is the fire
before the fire approach which I'm told has been used in large scale kilns
and producer gas making schemes, drawing air over coals and switching back
and forth between two fuel magazines. I'm limiting my thinking to natural
draft, because the world's that we work in are not yet at electrical fan
stage. Once a bed of coals is established there are maze like configurations
that would force hot flue gases into closer contact with glowing coals. I've
tried two or three of these approaches without noticing vast improvements. A
downdraft downfeed fuel magazine where the wood is vertical and burns at the
bottom tips preheats primary air a bit and it is a cleaner arrangement but
folks don't seem to like having their fire at the bottom of a well. So, I'd
love to have someone figure out how to substantially preheat primary air to
say 1,000F. That should make any stove much cleaner burning, I would
imagine.

As far as heating secondary air goes then don't we often run into the
problem of creating top feeding? The natural draft Z stove (top feeding)
used natural draft to pull air past the metal cylinder of the combustion
chamber and made nice blue jets of flame as the hot air entered the flame at
right angles. When you try the same arrangement with an open horizontal feed
magazine (which is what folks seem to want in Cental America) the effect is
less noticeable, I guess because most of the air is flowing in the
horizontal hole. If you have a strategy that includes horizontal feed I'll
very gladly try it and see what happens. I don't know if we need more air
above the fire or not. Is the fire starved at that point or does enough
excess air flow in that added air might not be needed? I'll refer that
question to the experts at Colorado State Engine Lab. Hopefully they can
answer this question for us...

Be grateful for any help,

Dean



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