[Stoves] The time-temperature-turbulence equation

Lanny Henson lannych at bellsouth.net
Sat Oct 5 07:49:03 MDT 2013

Another problem with a concentrator ring is that it blocks the radiant heat.
If you are using a fan you should have enough velocity to mix inside the burner. 
Having enough velocity without a fan is more of a challenge. I use a low friction airflow path and draft and I am able to get mixing below the pot.
Instead of using a concentrator ring in my SLC I do the opposite. The burner increases in diameter at the top to give the pot a larger "radiant view" of the fire.
If the air enters the burner in a near tangential way you will get a fire tornado and a tall flame and that is also a problem.
I am testing a stove today using different types of wood.

  ----- Original Message ----- 
  From: Crispin Pemberton-Pigott 
  To: 'Discussion of biomass cooking stoves' 
  Sent: Saturday, October 05, 2013 8:56 AM
  Subject: Re: [Stoves] The time-temperature-turbulence equation

  Dear Jock


  >When I read your "In the time-temperature-turbulence equation" lights went off.  


  I would rather hear they went on.


  You are quite correct in your analysis, though be careful about generalising on the other approach.


  >I expect this is why my iCans with three washers as deflectors, in contra distinction to a "concentrator ring", burn cleaner.


  Correct, with the proviso that the concentrator ring could be better it is broke the incoming (lateral) flow towards the centre into jets. The point is to get turbulence while not shortening the residence time 'at temperature'. The easiest way improve the concentrator ring is not to have one in the first place, but to create the same effect using hot secondary air jets. The result is you can drop fuel in without hindrance and there is one less part to make.


  If the ring is a necessity, make it using a concertina-forming tool so the gas flow is divided. Anything to make it not be a smooth flow like water going down a round hole with a radiused edge.  


  This is particularly important when the excess air level is low because it is hard for the H and C to find O2 when it is in short supply without turbulence.


  >They are essentially soot free.  Perhaps "soot free" should be a goal?


  Correct again. 






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