Fluted gasifier with tube screen grate; This is what I think the air/gas flow would look like.
It would result in a large elliptical “hell hole” where the gas goes into the exit pipe. It looks like to me, the holes in the flute would have to get larger going from where the air enters to the other end. Probably substitute the screen grate with maybe a solid flute again with the nozzles openings going from large to small as they go from one end to the gas outlet end.. I don’t think a screen grate will pull a vacuum all the way from the gas exit end to the other. $.02 TomC