Hey guys I’m sure you won’t be as happy as I, but I remembered what the other question was the other day when I had brain fade
Question about SECONDARY BURN. I have made charcoal with a TLUD 55 gal drum. I put two pieces of rebar on the drum and sat a hollow drum on top to increase SECONDARY BURN. So I have seen it, and done it, but I don’t understand it. So maybe to avoid long dissertations on theory I’ll get right to the question.
I have an old used double 55 gal drum wood furnace / burner. I am thinking about rebuilding it with new barrels. You know how one barrel sits on top of the other and the two are connected with a short piece of 6" stove pipe. If I put holes in the 6" pipe can I get a secondary burn in the top barrel?. TomC
So you are saying this only works with incomplete combustion? If I see smoke coming out of the chimney does that mean I have incomplete combustion. If I add holes in the connecting tube will it ignite automatically from the lower burn or do I have to add ignition to the secondary air? Sorry, but I just haven’t gotten my mind wrapped around secondary burning.TomC
PS Also having trouble with “rocket furnaces” not “rocket stoves” Later subject.
I ain’t no expert. But your smoke needs to be strong enough to burn. One way to think about it is stages combustion. So the first stage needs to make a self burnable smoke. I’ve made thingies that made weak gas that only would stay lit by using another flame or glowing char.
The octane rating of the fuel does not alter the energy content of the fuel.
Subtract the ethanol content and they are identical.
How the fuel behaves is a different question
Some engines will run better on a lower octane fuel and produce more power.
Its really hard to pin down exactly why but its got something to do with the lower compression and the fuels resistance to ignition ( ping or otherwise ) and flame speed.
One engine I built was actually slower on 100LL.
It needed the octane but the flame speed of 100LL a fuel designed for slow turning aircraft.
With fixed timing there were times when the piston was outrunning the flame front at high rpm.
Blending helped but in the end I resorted to simply adding Xylene to 91 octane until I found a mix that was just right.
In all cases however its the way the fuel burns in the engine that makes the difference in fuel economy when the alcohols are removed from the equation and not the BTU content that’s for all practical purposes identical.
This build is still very confusing to me. They put in a smaller burn chamber and then they insulated all around it, I presume to keep the smoke hotter until it gets to the secondary air. And then the chimney is so close to the secondary air that it seems to me the heat would go right up the chimney, with very little contact with the top of the larger barrel.
With the old burn barrel system, you had a larger burn chamber and heat would flow through the walls of the burn chamber. I believe we get a lot closer to complete combustion in the first burn chamber ( for this new way to work you have to hold back on air and create partial combustion in the small barrel ). The second barrel of a two barrel, is just taking heat off the exhaust that would have gone up the chimney.
Thanks again. I am always interested in new ways but my “bull” head gets me to pass on some that I probably should have given a better chance.
Tom, I think he is storing some heat in the sand and maybe easier on the barrels. He also builds a smaller fire. He also said you can add the second barrel on top. Also two places to cook on.
Tom, I would call that more of a continued burn as well as a secondary burn. The air in a TLUD comes from the bottom and is limited so that it it creates an oxidation zone that moves farther and farther down the barrel and gets used up in that process so there is not enough oxygen left to burn up the charcoal that remains near the top of the barrel. The unburned products of combustion rise through the glowing charcoal and exit at the top and would rise uncombusted unless the top barrel is there with added oxygen and heat containment which completes the burn and produces no or little smoke.
If you lay that on its side in the case of the barrel stove, the fire will migrate to the loading door and burn everything up as it goes toward the chimney pipe. If you add air holes back there you might not do any more than reduce the draft. I tried that once with mine by opening a one inch bung hole in the back upper barrel that happened to be located right by the 6 inch barrel connecting pipe. I thought I might see some secondary burn there but there was not enough energy left in the smoke to burn again. That’s my 2 cents worth and maybe that’s all it is worth:grinning:
Headed back to VA tomorrow to visit my sister’s farm. There’s a strong chance I’ll be moving down there semi-permanently, to work on the farm (and build gasifiers).
It’s one step closer to where I want to be… On a farm, eating food I grow, using energy I produced, building things for people. Kind of exciting.
Maybe if your primary air in the lower barrel was bottom-fed through a slotted tuyere like a naturally-aspirated forge instead of from the front/door, your stove would act more like a TLUD/gasifying stove than the design you’d described?
Hope you got nieces and nephews also. They are so fun to teach how to wipe their noses on their shirt sleeves and moms really appriecate appriecate it. : ’ )
I’m with Tom. But without a sketch I can’t picture of how it should be built.
I understand to let air in under the fire and that is the primary burn. What then? Just any air above the fire is a secondary burn? Or should it be preheated along the outside of the burn tube and piped in above the fire?
Don you cut right to the meat of the subject YOU TRIED IT IT DID NOT WORK. Thank you. You have save me a lot of time. I have enough projects in the fire and don’t need to start another BUT getting heat in my shop right now is pretty important. I have a wood stove now but it eats up wood and doesn’t get my shop very warm ( if the building is not insulated, no stove will warm it ) So after your experience I will look for insulation instead of more heat. Thank you. I’ll give you the two cents the next time I see you because your explanation was well worth it.TomC
