This is a stoker-burner that I built in 2006. I have used it as an experimental rig making only minor alterations from time to time. It has successfully heated my house for four winters and I have only just completed its replacement. The construction is very simple indeed, conisting of a hopper, a feed-tube with auger (large rotating screw shaped bar) and a burner-head. Fuel is simply fed in at a known rate and mixed with air. You can see the resulting flame which I can confirm is hot even when standing six feet away. It is very similar to an oil-fired central-heating system, in fact, I use the water jacket from such a system to collect the heat from the flame. This system is quite impressive and I still have difficulty believing that something so simple can work so well. (Click on picture to enlarge)
Another photo of the same stoker-burner but after the burner-head had been modified. The burner-head was the most difficult part to get right as the correct airflow is critical. More sophisticated units, including my updated version, have reflective (refractory) substance surrounding the inside of the burner-head. This makes a hotter and more efficient combustion zone. The idea is to have a small but very intense fire so all of the fuel and gases are burnt cleanly. Note that there is no smoke from the burner itself, just from some grass and ash on the ground. (Click on picture to enlarge)
This is the view into the burner-head once the fuel has been stopped and the flames have died down. The flames do not just shoot out horizontally from the tube but rise vertically and curve over towards both sides of the tube and then exit nearer the top. The partly combusted wood can be seen at the bottom, there is no need for any mechinism to remove the ash as this naturally falls from the end of the tube under the action of the hot gases. Roughly 200 litres of wood-chips will last about 10 hours and will easily heat a medium sized house. All that is left afterwards is 1-2 litres of very fine ash for the garden. (Click on picture to enlarge)
On a day when things weren't going too well and I couldn't make the burner work the way I wanted, I quickly threw this little offering together just to convince myself that I could at least make something work. The tube is closed at one end and a fan is attached so that a blast of air enters at 90 degrees to the tube causing a rotating vortex of air to travel along the tube and out of the open end. Next, a handfull of woodchips is dropped into the tube and the fan is temporarily removed so that the chips can be ignited with a hot-air gun or similar. Once alight, the fan is put back an we're off. If nothing else, it's a good bit of fun and it makes the most glorious noise! Two words of warning: 1) The tube heats-up a lot quicker than you might expect. 2) Avoid using a lighter as it's very easy to drop the lighter into the tube in all the excitement to get the fan back on, with obvious consequences. I use a hot-air gun to light all my experiments for that reason. (Click on picture to enlarge)
This was an earlier experiment where the burner-head is an old gas cylinder. This one did have fire-bricks (which reflect heat back to the fire) but gave me many problems because I didn't understand how to get the airflow right at that time. Eventually, I abandoned it and moved on. I think with a little more patience it probably would have been fine in the end. Note the two fans, I've since found that one is more than enough. Again a word of caution. Unless you know exactly what you are doing DO NOT touch a gas cylinder. In any case, you must have the permission of the owner first. The gas cylinders I use have been damaged and are re-claimed from the scrap-man. EVEN SCRAPPED OR EMPTY CYLINDERS ARE STILL EXTREMELY DANGEROUS - PLEASE BEWARE!! (Click on picture to enlarge)
