I found these were quite good overview articles:

http://www.lowtechmagazine.com/2014/06/thermal-efficiency-co...

http://www.lowtechmagazine.com/2014/07/cooking-pot-insulatio...

There's an irregular community around the 'Rocket stove' concept who seem to love playing around with different stove designs. It's briefly mentioned in the article, but it's a good starter term to search if you're interested in more information.

An experiment I've always been interested in trying, but lack the tools to carry out, is to take a nice dry unsplit log and drill/file the core out of it in a somewhat conical vent shape. It would be interesting to see what it would look like if you could get the log burning on the inside with the axis vertical and good space for airflow underneath.

This is only related insofar as the term 'rocket stove' reminded me of the plan, but I thought it was worth sharing in case anyone with a woodworking router in their garage wanted to give it a try.

Stoves can be fun. Spend much time talking to backpackers and you'll find a few who are constantly experimenting with how to cook faster, more efficiently, and with simpler lighter rigs. It's their hobby.