[Stoves] Secondary air in Rocket Stoves?

[Marquitusus]

Hi to all,
In the ETHOS 2015 Dean Still's presentation he states that:
"In	a	Rocket	stove	only	forced	air	mixing	results	in	almost	complete	
combustion.	Strong	jets	of	air	are	needed	to	fully	mix	the	air,	flame,	
smoke,	and	gas.			
Adding	a	chimney	to	a	Rocket	stove	doesn’t	result	in	the	forceful	jets	
that	create	adequate	mixing.	Adding	height	to	the	Rocket	combustion  chamber,	while	giving	more	time	for	combustion to	occur,	also	draws	
in	more	cold	air	that	results	in	more	wood	being	burnt."
I was wondering if this "forced air mixing" should came from natural draft. For example, at some distance above the combustion zone, we can make some holes in the chimney allowing secondary air to enter and mix with the hot gases, creating a secondary combustion zone. Maybe we can put a "concentrator ring" above the holes like in a TLUD to create some turbulence.
This done, we can also increase the chimney height without the problem of "drawing more cold air that results in more wood being burnt", as part of the increased draft suction will be used to pull the secondary air inside the chimney.
With this tall chimney, hot gases can have more "mixing, time and temperature" to achieve the desired complete combustion.
Anyone tried something like this?
Some questions arising:- What distance above the primary burning zone should we put the secondary air?- What number and size should be secondary air holes? (we can take experience from TLUDs)- What size should be the concentrator ring? (we can take experience from TLUDs)- What height should be the chimney after the concentrator ring?

Marc
 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150522/8e8385f2/attachment.html>