lawry
Junior Member
Posts: 113
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Post by lawry on Jul 22, 2016 14:32:55 GMT -8
shilo started my fascination with exhaust gas recirculation... I thought about it and procrastinated about implementing it... Then I saw a video about a charcoal retort kiln, which basically uses wood gas from the charcoal material as input energy. I was motivated by the videos. So i made changes to my outside stove. I tapped the gas from just above the riser then to the firebox. vimeo.com/175894394See the smoke on the right coming into the firebox.... Problem I decided to insulate the pipe from bell to firebox. But Then the gas went in the opposite direction.!! I was really hoping to see wood gas catching fire... Any idea how to keep the gas going in the firebox direction??
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Post by patamos on Jul 22, 2016 15:11:07 GMT -8
That is the challenge,
The push and pull of these gas flows is ever-shifting with varying rates of combustion
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Post by pianomark on Jul 22, 2016 17:59:00 GMT -8
If I understand the theory correctly, in a properly operating rocket stove all combustible gasses will be burned in the extremely hot riser. That's why the riser must be well insulated, to concentrate the heat in the burn zone. There shouldn't be any combustible wood gas left in the exhaust stream beyond that.
Not sure why you think there might be unburned wood gas present anywhere past the riser, but if so, wouldn't it make more sense to try to get a complete, clean burn the first time through? As opposed to allowing incomplete combustion, and then trying to recover (only a portion) of the unburnt fuel. Am I missing something?
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Post by patamos on Jul 22, 2016 18:41:56 GMT -8
Naw, there should be nothing left to burn. But Shilo was thinking that maybe the injection of any kind of air in the optimal location, rate and trajectory could enhance the turbulence in the burn. The idea is to reduce excess oxygen as much as possible, but still have the advantages of greater air flow where you want it. I haven't been keeping up with the boards, so may have missed Peter's interpretation of data from their recent experiments with EGR and Chet portals.
It is otherwise conceivable that the EGR could slightly improve combustion efficiency in the early and late/coaling stages of a burn by recirculating unburnt gasses. And/or to a minor degree do the same during a stack drop - much like Peter's trip wire and J-feed P-channel.
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lawry
Junior Member
Posts: 113
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Post by lawry on Jul 23, 2016 0:44:52 GMT -8
It is otherwise conceivable that the EGR could slightly improve combustion efficiency in the early and late/coaling stages of a burn by recirculating unburnt gasses. And/or to a minor degree do the same during a stack drop - much like Peter's trip wire and J-feed P-channel. This is exactly why I am tinkering with this. Well... Its also fun to tinker.đ The other scenario is when the stove is in over firing mode, it produces a dirty burn. If we could redirect the excess gasses back into the box then we should get more heat. Today I will remove the insulation and try again. I will update. "Without experimenting we won't discover new things.... Even if it is by mistake... "
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Post by peterberg on Jul 23, 2016 1:33:50 GMT -8
Redirecting the exhaust gases to the firebox would mean the pressure in the firebox/port should be lower. I hate to disappoint you, but the whole system is operating in underpressure as it is, although not everywhere in the system at the same value. Feeding exhaust gases at a low pressure into the EGR assumes an even lower pressure in the port, otherwise the stream would go the other way around. Which would be a bad thing, since more unburned volatiles would end up in the exhaust gases then.
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lawry
Junior Member
Posts: 113
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Post by lawry on Jul 23, 2016 5:28:28 GMT -8
I hear you PvdB... The gasses came down. So I'll give it a shot. I will report back here with whatever I find. I am having fun experimenting. In the mean time have a look at this video of the James hookway retort kiln. The heart of this kiln is an L shape rocket linked to the charcoal chamber. It is clear that the charcoal chamber is at a higher pressure. youtu.be/nhqFsCuo058
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Post by ronyon on Jul 24, 2016 8:58:27 GMT -8
Perhaps a one-way valve could prevent the gas from running the wrong way?
The Hookway has always been interesting. The fuel makes a relatively poor insulator,I believe the structure is metal,but making charcoal is a great thing.
When I build my rocket oven,I will be including a pipe to return gasses to the burn chamber. I hope to "bake" willow in the oven,turn it into charcoal and get a longer burn...
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lawry
Junior Member
Posts: 113
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Post by lawry on Jul 24, 2016 9:47:11 GMT -8
Yesterday I did another test. It seems the gasses go back up when I open the door. Which makes sense. I'll put thin strands of ceramic fibre on the top of the pipe coming in to the firebox across the opening to indicate flow direction throughout the burn.
I like your idea Ronyon. So you'll have two fuel supplies. The other producing charcoal. BRILLIANT! When you don't need charcoal the It's a normal stove. Maybe the charcoal chamber could double as an oven. After thorough cleaning..
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beau
New Member
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Post by beau on May 3, 2017 9:19:13 GMT -8
Any update on this? Video link not working.
Working on making a charcoal retort and was wondering if there was a way to use a rocket stove and redirect the gases to heat a charge chamber.
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stoker
Junior Member
Posts: 61
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Post by stoker on May 3, 2017 16:02:35 GMT -8
Shilo was thinking that maybe the injection of any kind of air in the optimal location, rate and trajectory could enhance the turbulence in the burn. The idea being to add kinetic energy, stirring things up and therefore helping? I remember reading (in a multi-volume book called "Steam Engine" published in the 1890s) about some experiments with injecting live steam into the fire in steam boilers. It gave some impressive results (at least visually) but some of the metal bits in the fire didn't last long. So yes, stirring things up like that can help. But the steam was under pressure, whereas post-combustion gases will always be at lower energy (pressure-speed combination) than the firebox (at the same height). So I think EGR can't help in a stove, except perhaps if there's a fan or gas-pump involved... but there are probably better ways to use one of those.
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Post by pigbuttons on May 3, 2017 18:36:48 GMT -8
Even if you were to get the gases to re-enter the firebox, like was said before - if your rocket is running properly there won't be much if any fuel left, and the point I'd like to introduce - it will be oxygen depleted air as well. So the best you can hope for is some extra heat into the flow, but the only way to get the gases to fall enough to enter the firebox is by cooling them.
The only way I see this being of any value is to have the heated air continue up into a second fire box that is higher than the riser exit after mixing with oxygenated air. You would gain heat and velocity and could control how much fresh air is mixed into the flow.
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lawry
Junior Member
Posts: 113
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Post by lawry on May 6, 2017 13:56:28 GMT -8
pigbuttons my thinking was that in a over fuelling situation then the fuel can be Re-Burned.
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Post by pigbuttons on May 6, 2017 21:17:48 GMT -8
pigbuttons my thinking was that in a over fuelling situation then the fuel can be Re-Burned. Just thinking out loud here but, you would have a potentially hazardous situation if you are sending HOT fuel through a pipe to a possible ignition source. If you hit the magic air/fuel ratio, all of the fuel in the pipe will ignite at once; best case is it makes a large bang and blows the fire out, worst case is it violently ruptures the pipe. You may want to look up "pulse jet" if you don't know the principle, it amazes me still that such machines actually work. Rocket stoves, in my opinion, are interesting because a well built one runs at super high efficiencies at burning wood. If it were my project, I'd focus on getting it to run at peak performance the first time through the stove. The secondary burns in the stack or at the secondary air supply are in the primary fire path and therefore less likely to create over pressure scenarios, though stove runaway roughly falls into this category. Clean, hot, efficient, would be where I'd spend my cycles, then proper use downstream of the energy produced. Sorry if I sound like a nay-sayer. Just my opinion, not trying to troll you.
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lawry
Junior Member
Posts: 113
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Post by lawry on May 6, 2017 23:31:55 GMT -8
Fuel can be pre-heated. Check the TLUD discussions. There's a "charcoal retort" that runs off its own fuel /gasses They still work...
I use experimentation to improve my knowledge. I did so with this experiment. I have already moved on from this idea. I have designed my own firebox because of this knowledge.
Nay-sayers assist with the thought process too... All comments are welcome.
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