I'm imagining a (well-insulated) firebox in which a large chunk of wood is loaded vertical, with a bed of coals at the base, fed by primary air holes. The gasses from that would exit at some height into a secondary burn chamber, then into a bell. The wood would ideally burn mostly at the base, gradually feeding itself downwards. Reloading could release smoke and flammable gas if measures aren't taken to prevent that. Forced draw might work. A centrifugal fan would provide pressurized air, which could be blown into the flue in a way to draw air from the firebox via the Coanda effect, overpowering the convective force when you open the top. That might be easier than a fan directly handling the exhaust from the flue. However, I did have one outdoor boiler with a centrifugal fan with styrofoam blades mounted on top of the chimney, and those blades never melted (the unsealed computer fan turning it eventually died from creosote). I suppose the wood could be loaded from a lower door (wear an oven mitt?). I suppose there are other options, such as two fireboxes to swap between (loses the benefit of a hot firebox) or a separate loading chamber with a mechanism that opens an inner door and pushes the new wood in (seems overly complicated). An online search didn't show any existing designs for vertical-fed fireboxes, so I'm wondering if anyone here has thought about the concept, or can see some obvious flaws. A chunk of wood horizontally could burn from one end, but would require moving the primary air supply as the burn area moves. I suppose I could build a simple rocket stove outside with a vertical firebox and see how it works, and how it doesn't.
