JesseN., actual Imbert was a man who had original patents on a system beginning in the 1920’s, up through the 1950’s? He was able to get investors and set up commercial making manufacturing concerns in different places throughout the world.
His systems were for light weight mobile applications. Had formed walled hearth core flows shaping. Means always direct contact of the hot glowing char, the different stages of gas flows, and released hot ash direct contacting against those cast metals walls. And later some WWII German system with ceramic cast walls.
These are small active volume internal area units. Rely MUCH on high flow velocity internally to function well.
The later; BETTER, Nordic ash-slope systems were much more durable, easier to manufacture, and maintain in actual service.
Still velocity-as-king, dependent biased systems. The design math’s for both are similar and here in the Library section.
The WK is a large hearth core active area volume system. No nearly so much a flow velocity dependent. Uses a longer TIME-in-residence bias. Said to be FEMA derived. Hmmm. Actually very related to the older town stationary gas-plant gas makers.
Has it’s own design maths. Published in Chris/Waynes book. Discussed much by builders here on the DOW WK-builders premium side.
Then . . . . there is the Dobson systems. HUGE internal volume, with all-active, super HIGH throughout Temperatures, with low velocity and l-o-n-g, l-o-n-g, gas-in-residence Times hearths. This type is larger, heavier, and has not proven amiable for mobile use.
For the internal system bias’s of LONG Time-in-residence, with huge active internal volume the Community Power Systems and IISc/Mukunda systems are very related. Without the Dobson super high Temperatures.
These last three along with the old big gas-plant systems will post up fuel-weight to gas-out volume conversions efficiencies that the smaller, lighter made systems cannot match.
Good example that an absolute single-stage efficiency is not the goal!
It’s what the system can and will do for you! Converting your own, owned resources into measurable productive working for you and yours.
Of course there are other systems types.
But I only concern about those able to use site grown woody materials as fuels inputs. With the least, minimal processing of those woody fuels.
The all-fuels-stocks must-be ground-up. Some needed pelleting or artificial made-up chunk/pucks “fuel”. These systems are not in my opinion DIY doable. Or desirable.
Too many special-needs fuel making steps. Requiring too much machinery. Driving into Too high of make-it-work capital investments.