Blue and reddish gas flames where sucked into the flame tunnel

At the workshop of Hans Baarslag in Wierden, the BrickStove waited for a test. New to be tested were three items:

• the lining of the fire box made from thin stainless steel sheet (0,5 mm),
• the new set up of the conical funnel, the 'catch' where the wood from the container gets stuck, while sliding into the fire box,
• the ash tray, also folded from sheet metal, that takes part in guiding the burning gassified wood into the "flame tunnel".

Thanks to the link we got from Sasha I now understand better the two phases of wood burning: first the gasification of the wood, followed by the burning of the gas. Air (oxygen) for such secondary burning is still available in the gas mix or streams in through a second opening.
Actually these two phases could well be observed through a glass window: wood, while it was burning and smoking remained stuck into the catch. From time to time charred peaces fell off, lining the ash tray with burning charcoal. Blue and reddish gas flames where sucked into the flame tunnel. (see top picture)
The steel sheet lining for the bricks, the shape of the 'catch', the ash tray and the entrance to the flame tunnel, all seemed to function as foreseen. However not so the in-flow of air.

So we reconsidered the idea of pre-heating air, similar as is done in steel furnaces. As the BrickStove is build now, cold air from outside is pre-heated when it flows along a metal separation in the flame channel. It then flows under the ash tray and enters the fire at the front, the place where the window is positioned.
This functions only partly. Because the fuel (wood) container still has a very rough fit in the top of the BrickStove, a part of the air sucked in by the ventilator, leaks in through this bad fit.

rough scheme of the new setup

Joel Fransen, Demotech's new intern from the Design Academy in Eindhoven, suggested to make this accidental air leak the one and only entrance for fresh air.
This is a nice kind of break-through idea, upsetting the present basic set up, but giving another simplistic layout in return. With Hans I planned to build a second stove in this way (see rough scheme of the new setup).

1. Fuel container, filled with anything solid that will burn.
2. The conical funnel, the 'catch' where the wood from the container gets stuck, while sliding into the fire box.
3. Flame tunnel and interior space where the burning gasses transfer their heat to the stone exterior.
4. Exhaust to ventilator. Forced draft sucks in the air at the fuel container, blows it outside.
5. Brick exterior heats up while the fuel container feeds the fire. Its outside radiates its heat outwards for a long period after the fire is extinguished.
6. Top of metal sheet can be removed for inspection and repair.