I revisited an earlier secondary air concept that used 3 triangular ports at 120 degrees around the fuel can. Importantly, the the third side of the triangle was bent down into the fuel can to create a vane to increase turbulence.

What I did today was to add three deflectors above the secondary airports/vanes. The deflectors were positioned midway between the ports and just below the top of the fuel can. Thus when the draft can was added, there was effectively no secondary air gap at all.

While this is only one run to see if the would work, the results were very good. Lots of turbulence. Some good flame noise. At the 15 minute mark I put on a 19 oz can of very cold tap water to boil. It boiled in 15 minutes. After about 30 minutes over the flames and in the flue, there was only a small amount of soot on the "pot". The pot bottom was NOT black. Ambient air temp was about 45f. Little to no wind.

A few pictures:

Jock Gill, Vermont, 2011

Jock's new TLUD Design. It has a passing similarity to Lanny Henson's Sidewinder, but instead of 4 symettrical slits, to provide the 'vortex' at the heart of the cooker. The iCan D uses only three secondary air apertures for maximum turbulence and asymmetry. It also uses a more triangular cut arranged such that the resulting tab is at 45 degrees and can, when folded into the can, act as both a vortex generator and a concentrator.

Currently I have only tested the mid-sized coffee can unit with 142 grams of fuel. This gives me a runtime of about 27 minutes -- start to flame out. It has yielded 21.8%% biochar as a percent of weight of fuel -- soft wood pellets.

It gets good results when loaded with 25% of the capacity of the can - in this case about 142 grams of wood pellets. Run time: 27 minutes. Smoke gone in well under two minutes. Biochar was very clean, 100% charred fuel with no floaters in a water quench. Minimal ash. Biochar harvest was 21.8% of the weight of the starting fuel load. Only minimal soot in the stack gases for about 3 minutes at the peak period.