ARC E-Newsletter 7/3/25: The Concentrator Ring in a TLUD

[Aprovecho Research Center]

The Concentrator Ring in a TLUD

Image from Dr. Paul Anderson’s Introduction to TChar (TLUD) Stoves for Haiti

The size of the hole in the middle of the flat plate, usually round, that seals the top of the combustor in a TLUD (top-lit updraft) stove has important functions. The flat plate forces air jets/flame to travel horizontally in an attempt to completely cover the fuel bed. The diameter of the round hole has a dramatic effect on firepower. When it is too small, the fire can even be extinguished.

As with other variables, iterating changes in a prototype under the emissions hood can determine the compromise that best meets project goals. Larger holes in the concentrator result in higher firepower but can also increase emissions. In a 5” in diameter stove, a 3” hole in the middle of the concentrator is commonplace.

In the StoveTec FireFly lantern, developed at ARC, a small hole in the concentrator ring (1.5”) forces the flame into a narrow, vertical cylinder used for illumination. While the firepower is very low, so are the health-affecting emissions per minute.

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