I stumbled on the "
Rocket Stove" this morning. The flames travel sideways, burning all gases—even smoke and ash—from twigs and smaller,
un-split, pieces of firewood. It vents whatever's left at ground level. (What's left of the firewood is moisture and CO2). It's said to be a "controlled chimney fire".
On the downside, the "rocket stove" is one hungry woodstove!
But I suspect that's an indication of its efficiency.
In the first picture, the entire length of the "couch" is heated. A large thermal mass is contained within. The "thermal mass" can be rocks, bricks, or sand to hold and radiate heat.
The "Rocket Stove" didn't turn up on a search.