The stove turned upside-down, with soon-to-be-charred sawdust loaded in the outer chamber. The plate to the right attaches onto the bottom to keep a tight seal, while the small holes between the inner and outer chamber allow for gas from the charring sawdust to flow into the inner combustion chamber.
The stove with the plate attached to the bottom, and turned right side up. The center combustion chamber is about 3/4 filled with some dry wood chips.
This being a "TLUD" design, the combustion chamber is "top-lit up-draft." You can see some smoke coming from the initial burning of the wood chips.
As the combustion chamber heats up, the UD in TLUD, "up-draft" comes into play, sucking in air through the grate on the bottom plate. Still in the initial buring phase, the outside of the stove is just starting to warm up.
As the sawdust feels the heat from the center chamber, it is gasified, turning into syngas, or a combination of hydrogen gas, carbon monoxide, and methane. The syngas, short for "synthesis gas" serves as a major source of fuel for the stove, and is smokeless when burned, creating enough heat to turn the steel lid various shades of blue and purple.
The wood chips in the combustion chamber burn down, but there's still a lot of fuel left over in the outer chamber.
The seal on the lid is crucial, as gases produced in the outer chamber will try to escape out the top, rather than being sucked through the holes to the bottom of the combustion chamber.
Even after all the wood chips have burned to ash, the flaming gases from the sawdust in the outer chamber keep coming through to the bottom of the stove, directing more heat upwards. In this picture a rudimentary piece of metal on which to rest a pot is placed on top of the stove.
When all was said and gasified, the sawdust in the outer chamber turned into this beautiful char.
