[Stoves] Concentrators in ND TLUDs

[Paal Wendelbo]

Dear Paul

No doubt you are the first to use the name concentration lid, but probably not the first to utilize it. It is not very important, the most important is that it is utilized to improve the combustion into the TLUD-NDs and that it has got a name. I just called it top lid due to the fact I used it from the very beginning in 1988 and had no other choice.



      Aprovecho 2009
     
     Rocket

      Mud with skirt
     Rocket

      Haiti side air 
     Rocket

      Haiti


       Peko Pe
     Multi Use stove


     Toucan


     TLUD

      Champion 
     
      Fuel to Cook 5L 

      (8 50/1500) g
     g
     666.6
     1046.4
     809.1
     768.8
     2749.5
     925.2
     1075.7
     
      CO to Cook 5L (20)
     g
     59.2
     2 50.5
     27.4
     23.0
     67.3
     52.0
     90.5
     
      PM to Cook 5L (1500)
     mg 
     1656.2
     3267.8
     3060.6
     223.1
     3191.6
     2059.9
     9904.4
     
      Energy to Cook 5L15,000/25,000mkJ
     kj
     12,839
     20,153
     15,582
     14,807
     52,954
     17,818
     20,718
     
      Time to boil 5 litres min
     min
     48.4 
     47.7
     26.4
     28.1
     30.6
     18.9
     25.0
     
      CO2 to Cook 5L
     g
     1307.7
     1716.7
     1395.5
     708.6
     843.8
     1052.5
     1098.4
     














With reference to the Aprovecho informal test in 2009 where Peko Pe got the KSHKW award for the cleanest burning THUD-ND, it is maybe possible to improve the efficiencies a bit; and that is what is done with the new horizontal Peko Pe II and III where the pot will came closer to the glowing char. 5 liter from 20 C ˚ to a boil within 27 minutes with 500 gr fuel and 100 biochar left.

It will always be possible to improve products, but the main thing the price and the acceptance by the end user. 

Best regards Paal W


From: Paul Anderson 
Sent: Saturday, February 23, 2013 9:26 PM
To: Robert Fairchild 
Cc: Hugh McLaughlin ; Tom Reed ; paaw at online.no ; Christa Roth ; terra-matricula at hotmail.com ; Karsten Bechtel ; rongretlarson at comcast.net ; Discussion of biomass cooking stoves 
Subject: Re: Concentrators in ND TLUDs

Bob and all,   ( I am sending to the Stoves Listserv because the discussion merits a wider audience.   Please read Bob's message first (below my comments.)

Paul writes:
I like your analysis of the options.   And there are additional variations such as fins or "mixers" that could increase the turbulence.

I am not in favor of forcing the gases to the outside.   My reasoning is that when the gas flow is low (intentionally or otherwise), there can be loss of the flame on one side of the "ring-gap" and the flaming side is not able to re-ignite the extinguished side, allowing un-combusted gases to escape.

I think that the Reed-Larson 1996 natural draft IDD (now called TLUD) was not very successful because of the outside gap instead of the concentrator hole.   That led (I believe) Tom Reed to shift his efforts to force air units.   On the other hand, Paal Wendelbo's Peko Pe of the 1990s in Uganda had a concentrator hole in the middle.   I do not know when or how he started using the concentrator disk.   

I do know that my own early experiments were NOT very successful until 2005 when I (prompted by discussions with Tom Reed about mixing) first used the concentrator disk in the prototype "Champion" stove I took to Stove Camp where it won the Cat Pee Award for cleanest emissions.

Having said that, I must point out that the Belonio style of very successful rice husk gasifiers (with forced air only for the primary air) has a ring of holes (not a gap).   I will look further into this when I have such units in hand.

I agree with Bob that MUCH more useful experimentation is needed about this highly crucial aspect of TLUD stoves.   But there are no funds for such research (unless CSU will be looking into this), so I am sticking with the reliable concentrator disk in my stove project in Uganda.

Paul   (I will be home from Uganda by Tuesday night)

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.comOn 2/22/2013 4:28 PM, Robert Fairchild wrote:

        ND TLUD Concentrators

         It seems to me there are several possible concentrator designs for natural draft TLUDs. How many have been tried?

        Two dimensional concentrators include the ring (concentrating gasses to the middle) and the disk (forcing gasses to the outside). It seems to me that the disk might give better mixing and cleaner combustion as the width of the space would be narrower. (With a 6” cylinder, a ring with a 4” center hole has the same area as the gap around a 4½” disk. With the ring the secondary air needs to penetrate 2”, with the disk only ¾”)

        Three dimensional concentrators are the full venturi (back to back buckets –see attached photo, I tried it and it works just fine), half venturi, inverted venturi, and half inverted venturi.

        The half venturi – bottom bucket only - expanding to full cylinder above with ring. This might increase turbulence for cleaner combustion.

        The inverted venturi (back to back cones in the center – think 3D disc) and the half “inventuri” - bottom cone only. Again, the half version might increase turbulence for cleaner combustion. The inverted venturi, like the disc gives a shorter secondary air penetration distance than the true venturi.

        (Note: a venturi creates suction (to pull in more secondary air) at the constriction, Bernoulli “Where the speed is greatest the pressure is least”. It does, however, remove some energy (increases friction losses) and slows the primary gasses from how fast they would flow without the venturi.)

         Of course a disc or inverted venturi will need to be supported in the center of the cylinder with three or more radial supports.

        Thoughts?

        Bob

       



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