I have thought of the same thing you are fora long time. I have a forced draft option for my wood furnace, Its a US Stove Hotblast Wood/coal Furnace. My forced draft blower is on the back of the furnace right under the flame baffle. It goes into the stove, then from there its pushed through a piece of channel, which blows the air out the sides. I was thinking about adapting 2 pieces of heavy pipe one on each end, and drilling alot of holes in the pipe. Then run the pipes right under the baffle and have the holes facing the fire. This way you always get more secondary air to the fire. By the time the air goes through these tubes, it comes out hot, which then is easier to ignite the smoke. When the fan kicks on it pushes heated air directly on the fire. Now for coal this would do no good, but for wood, it would really help. These 2 tubes wouldn't take up any room in the firebox. I think it would work, and I have 1 1/2 OD 1/4 wall tubing, which would stand up to the heat. This would direct heated oxygen above the flames, which would help to re-ignite the gasses. I have also thought of putting a piece of steel on the baffle so when the smoke rises, it doesn't go apast the baffle right away, and keeps it there a little longer to be burned. These were just some ideas I have thought of. I have already rebuilt the inside of my furnace, its around 20 years old.
