Why do flames move toward the primary air inlet?

[wendell]

Third year with my Morso and something I've always wondered is why do the flames move toward the primary inlet? It would seem that since that is where the air is coming in, the flames would be moving away from it with the flow of the air. I always have a little blast furnace going on there, so much so that the glass there is etched.

 

[pastera]

I would say that it is because that is where there is enough O2 for the wood gas to burn. The rest of the box is starved for air and creates mostly wood gas that is burned in the secondaries or Cat.

Aaron