[Stoves] Natural Draft - with a vengeance

Tue Nov 8 18:29:05 CST 2016

Dear Friends of Natural Draft

Here<http://www.newdawnengineering.com/website/library/Stoves/Kyrgyzstan/KG%20Model4-Coal/TireRoaster/Tire%20roaster%201.mp4> is a video of a natural draft stove showing what is possible in terms of turbulence if the draft is applied at the 'right point' in the gas path. [10 MB]

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The fire pattern consists of two swirls rotating rapidly in opposite directions. The gap through which the flame is emerges is 80 x 100mm. The firepower is about 15 kW. Note that the space between the pot-cooking plates through which this was filmed is allowing air into the combustion chamber from above so the full force of the draft is not really in evidence. Closing the top plate increase the pull on the fire.

The fire is shown in two stages: about ½ power and then after the air controller is opened, full power. The velocity can be seen to change.  Also notice that the flame, which is about 1 foot tall and sits between the yellow glow at the bottom and the camera, is nearly transparent.

This is a crossdraft stove. The grate is shown at the end from underneath. The air enters the sloped grate and passes through the lowest portion of the fuel horizontally, taking pyrolysis gases to the 'deep end' of the grate through a pile of coke which is continuously replenished. Then the gases turn upwards into the view of the camera, burning as they do.

The chimney is only about 3 m tall - modest for a house installation. With 5 m of chimney the power rises to about 18 kW max. The thermal efficiency of this stove is over 90% in a typical installation, meaning with a bit of the chimney in the room.

This particular unit was designed by the guy on the right, based on the KG4 crossdraft stove. He intends to pyrolyse tires and burn the gases as a co-fired coal+tires heater.

Regards
Crispin

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