For the one or two people in the entire world who are interested in wood stove design, here is a pic of my home made stove while operating in "secondary" combustion mode.
The logs are not burning, they are in a charcoal-like state that makes them give off smoke. The smoke rises and mixes with pre-heated secondary air injection, causing the smoke to ignite if conditions are just right. The result is a very efficient fire that lasts a long time and doesn't give off much pollution.
At the moment I have a window open and the temperature in the shop is 80 degrees and rising. So most of the time I have to throttle the fire to avoid overheating the shop, and then the stove does not get hot enough for a secondary burn.