[Stoves] Trials on TLUD Gas Burners - Counter Current Flow

[kgharris]

Julien,

You always have such interesting ideas.  I have done a small amount of experimenting with injecting secondary air at an angle as you describe, but I used a much different arrangement.  My interest was how it affected turn-down, so I was looking for getting the air down as far as possible.  Straight down worked best for that.  I also had problems with smoke.  The downward flow seemed not to inject enough air into the wood gas, so I added holes above (method 4).  This helped a great deal.  I see you have no concentrator in the stove and I assume that is because you are relying on the terbulance from the counter flow to mix the gasses.  If I were working on this design, I would try to combine stove 1 with 2 or 3.  This would mean two secondary air entrances, stove 1 being an early secondary air flow, and stove 2 or 3 being the main secondary.  This would do two things, get the flame started burning early and add the main secondary air after the flame is already burning.  This will give extra heat to the secondary flame which will help to create a very hot secondary flame, making up for not preheating the secondary air, and finish burning the large amount of unburned wood gas mixed into the early secondary flame.  This should minimize the smoke and soot on the pot.  It also should provide turn-down if you control the primary air.  My current stove uses this idea of double burning and it works well.  I don't think stove 1's narrower combustor is the problem.  I think not having enough air mixed into the wood gas to make a hot flame and complete the burn is the problem.  Your stove 1 downward air flow will preheat the air as it descends before it turns inward to support combustion.

Good idea to experiment with,

Kirk
  ----- Original Message ----- 
  From: Julien Winter 
  To: Discussion of biomass cooking stoves 
  Sent: Saturday, August 02, 2014 8:52 PM
  Subject: [Stoves] Trials on TLUD Gas Burners - Counter Current Flow


  Hello stovers;


  This morning I woke up with an idea, and decided to give it a try.  It worked out quite well.  I put a inverted, conical ring on the top of a natural draft, top-lit updraft (ND-TLUD) reactor, and set a chimney on top of that so that secondary air could get in between the bottom of the chimney and the conical ring.  The rig is a bit like putting a cone kiln on the top of a TLUD.  The best burner had walls of the cone at an angle 60° from horizontal.  Secondary air was forced to enter the top of the TLUD in a downward direction, counter current to the direction of the pyrogas rising out of the fuel bed.  The result was a turbulent flame indicative of good mixing of gases.


  It is too early to say if this counter flow burner is viable, but is looks very promising.  It is also very easy to manufacture.  
  How to get the geometry for a cone can be found here: http://zenstoves.net/PotStands-Conical.htm#MakingYourOwnCone


  I have attached a pretentious blurb.


  Cheers,
  Julien. 

  -- 

  Julien Winter
  Cobourg, ON, CANADA



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