You seem to have the BRANDT gasifier in your mind!
It had the center tube filled with charcoal from above. But it started in the lower end ABOVE the grate!
Common charglow outside and inside this upward going (large) tube-end.
Also a version with a center-tube without charcoal was built and offered 1940, until the factory was bombed. Under the name PETSMO.
Both types were very metal-stressing!