Gasificationados (a made up name:),
Woodgas made by a gasifier sized and built to fuel a particular
engine has a wide range of chemical energy per cubic foot.
Operate the gasifier-engine slowly and the gas has a high chemical
energy content (but has more tar).
Run the system fast, and the gas has lower chemical energy content
(but less tar).
It is very hard to compare all gasifiers to each-other, but a
discription between the relationship of high and low gas-flow is
made in a series of experiments done by Dr. Tom Reed. On the web
visit: Biomass Energy Foundation. Key words to look for are:
The main thing I can see from his work is that given enough air,
all the energy stored in wood can be released as heat inside the
gasifier. Only hot-gas comes out that will not burn.
If your gasifier is too big for the engine, you get tar.
Other things need to be right also.
Balance is everything.