[Stoves] Turn down on FA-TLUD and ND comments

[Kirk H.]

Paul,

I think I can understand what you are saying so I hope I have it right.  I have found that during turn-down the excess cooler secondary air will fall into the chamber, cool the small flame, make it too lean to burn, and extinguish it.  This is because the small flame does not have enough lift to hold the air up.  Placing something like a ring over the chamber concentrates the lift of the small flame and reduces the amount of air the flame has to hold up.  Most of the air will be held up by the ring.  The small flame only has to hold up the air over the opening.  The lift is concentrated and the air load is reduced.  It does work.  A plate can work too, but is more difficult to make work.

Crispin’s photos appear to show the flames (TLUD ? or pressurized gas?) at a higher power level.  A good point for whatever kind of higher power flames they are, but it misses the point that you said low power.  As to whether it applies to TLUDs, the flames look like pressurized gas or coal rather than pellets or wood.  The central hole photo appears to be coal and not a TLUD.  Appropriate for your discussion?  We certainly don’t want our TLUD group misdirected.

Kirk

Sent from Mail for Windows 10

From: Anderson, Paul
Sent: Friday, February 15, 2019 8:57 AM
To: Discussion of biomass cooking stoves
Subject: [Stoves] Turn down on FA-TLUD and ND comments

Stovers,
  At my home (after TLUD Summit), Suddha and I tested the difference of a central buff body (block the middle) versus a concentrator hole (block the edges when placed on the FABstove TLUD-FA when the power was turned down.  

ABSOLUTELY CLEAR that the concentrator is far far far superior than trying to block the center.
Therefore, an easy turn-down with CLEAN combustion is accomplished by placing a concentrator over the top of the 100 mm diameter fuel chamber.  The hole size is proportional to the turn down:  fewer gases need smaller hole.  50 mm hole seemed quite reasonable.  
 
How to place this concentrator onto a functioning FABstove is a question.   Options are 
1.  to slide it in after turning down the air supply, or 
2.  turn down air, pull out canister, place on a top, reinsert a canister.  Or
3.  fabricate a closure like on cameras (a diaphragm) – tricky and probably not functional because of metal weakness and high heat.
4.  Other solutions.

NOTE:   This might only be used with certain cooking, such as wanting a slow simmer for a long time.   Using this could lengthen the time of operation of the stove to double or more.
This is also good to know for when there is a larger fuel chamber.

This has NOT been tested / compared regarding ND TLUDs.   There are at least two currently important designs.   
1.  The Champion TLUD-ND has a concentrator hole.  A very simple solution. Not much further work done on it.

2.  The Wonderwerk TLUD-ND by Kirk Harris has the combustion toward the edges of the riser by having centrally supported blocking, with several great ways to enhance mixing.

3.  What is not tried is to alternate from hole to edge or edge to hole (and back again, plus fixed-blades etc to get the mixing better.   Might not work???   So the tests are to send to edges (block center) after the concentrator hole, OR to bring together after having been mixed at the edges.

This might be a good boost for Norm’s larger TLUDs with ND.

Fair game for anyone to try.  Please tell us your experiences here on the Stoves Listserv.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu       Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com 


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