Here are a couple of sources for that wood gas generator info; it's a 90-page FEMA report with lots of figures and diagrams. The soil and health.org has a much cleaner version, whereas the dtic (stands for Defense Technical Information Center) version is official but a poor scan.
http://soilandhealth.org/wp-content/uploads/0302hsted/fema.woodgas.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a208249.pdf