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Anyone else recirculaing exhaust back into feed chamber?  RSS feed

 
Posts: 6
Location: Sullivan, MO
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Don't have an emissions tester to check out everything happening with the burn. Mentioned to Matt at Walker Stoves.

Just came back with the pipes, off the horizontal runs, back to intake. Mix of fresh and exhaust (mostly fresh, of course)
Shows no apparent side affects yet. But, I am looking for more investigation, as I continue with it.

Just wanted to see how the left over low emissions effected the total burn, if someone had a tester. Dirtier burn?

Can't beat recirculating the emissions for environmental effect. (I think, so far?)

Anyone try? Tested?
 
pollinator
Posts: 1947
Location: Cincinnati, Ohio,Price Hill 45205
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Neat! This reminds me of some vehicular charcoal gasifire builds, which route the exhaust gasses back into the air intake.
They do it to burn escaped fuel gasses, and add heat/draft to the combustion air.
 
Posts: 243
Location: near Houston, TX; zone 8b
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Fresh air has ~20% oxygen. Your exhaust should have less than 5% oxygen after combustion; a Dragon Heater combustion system tests out to this.

How is this little 5% going to help your burn?

So, if you are sending in your exhaust for another run, nearly 80% of what you are recycling is Nitrogen which is not involved in the combustion. If there is a lot of smoke in your exhaust, you have some other problem with your design.
 
G Fischer
Posts: 6
Location: Sullivan, MO
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William: That's kind of where I got it. BUT, vehicles usually have unburned fuels/fumes (inefficient as they are), where these guys (RMHs) don't have much except like Cindy says.

Cindy: Just wanted to try an all burn/no exhaust. Say, for an apartment that you couldn't have a vertical or horizontal stack drilled exhaust hole into the wall.
If a way to really have no exhaust. But, I do very well understand that at low draw/ending burns you wouldn't have the great draw to pull the exhaust back in
any more, and would have to figure out that stage or you would still need an exhaust vent.

I was just trying to see how feasible it would be, or even worthwhile enough, trying it. Will continue to mess with the idea. Makes the world go round. (Ha ha)

I am sure someday, in the not so far future, wood burners will get there.
Look how close RMH's come to it, now. ; )

 
Cindy Mathieu
Posts: 243
Location: near Houston, TX; zone 8b
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It can never be a good idea to burn wood without an exhaust to the outside.

I am sure someday, in the not so far future, wood burners will get there.


Where do you think wood burners need to be?

The theoretical limit of combustion efficiency burning in air (as opposed to pure oxygen) is 95%. Wood is fundamentally different from natural gas and propane in its burn characteristics. The mechanism for burning gas is very simple compare to what it takes to burn wood as efficiently. That is why the j-tube combustion system has to be so different from a fireplace with which most people are familiar. It is the only proven way to obtain something close to the theoretical efficiency limit. It is possible that another approach would do as well as the j-tube, but it hasn't been seen yet.
 
Mother Tree
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My son just read through this and said 'Um, isn't that how fire-extinguishers work?', and I think he has a point.
 
pollinator
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just wanted to add my vote to Cindy's and Burra's, One note, one vote ! Big AL
 
Posts: 1
Location: Around Barcelona
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Hi,
I was about to post the same suggestion. I've build a RMH before the winter. Works great, but after a couple deconstruction, I can see there is soot building up on the exhaust pipe, and on the barrel top & inside. I'm burning pine mostly, so I guess this is created at the beginning and end of each burn.

Anyway, I though about the "exhaust back into the intake" in a way turbo chargers work on vehicles. Apart from the concept, it is probably very different, as turbo are also adding pressure to the intake, and it is a 4 cycle system, as opposed to the RMH which is kind of a 1 cycle ; continuous system.

But I still imagine 2 ways the exhaust gaz has to increase efficiency :
1) The residual burn gazes that still have a "energetic potential" (only in the beginning, when RMH is not very efficient)
2) The gazes are relatively warm, at least 30 Celcuis so it would not cool the burn as much as it does when the air is taken from outside. And from what RMH is about, the warmer the burn, the more efficient it is...

Even if a properly built RMH, once heated up, is supposed to be very efficient, saving some emissions in the first 20 minutes is something.
But like some said, maybe replacing some oxygen by exhaust gazes would make the thing worst...

If anybody tried, please feedback.
 
Posts: 16
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A turbo does not send exhaust back into the engine. It does add boost /charge air, 5,10 psi or what ever the system is set for. The boosted charge is packed with much more 02. So you may be on to something there. In the old days the Blacksmith used a bellow to add air and get the fire cranking. I use shop air to restart if I let the fire die. As long as I see red coals at the bottom it will work. I drop a few small sticks and give it a small blast of shop air. The fire jumps right up and gets the sticks burning. Thanks Nick
 
gardener
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nick man wrote:A turbo does not send exhaust back into the engine. It does add boost /charge air, 5,10 psi or what ever the system is set for. The boosted charge is packed with much more 02. So you may be on to something there. In the old days the Blacksmith used a bellow to add air and get the fire cranking. I use shop air to restart if I let the fire die. As long as I see red coals at the bottom it will work. I drop a few small sticks and give it a small blast of shop air. The fire jumps right up and gets the sticks burning. Thanks Nick



http://www.gas-turbines.com/nt6/index.html

http://www.gas-turbines.com/t98-nt-xx/index.html
 
nick man
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Satamax Antone wrote:

nick man wrote:A turbo does not send exhaust back into the engine. It does add boost /charge air, 5,10 psi or what ever the system is set for. The boosted charge is packed with much more 02. So you may be on to something there. In the old days the Blacksmith used a bellow to add air and get the fire cranking. I use shop air to restart if I let the fire die. As long as I see red coals at the bottom it will work. I drop a few small sticks and give it a small blast of shop air. The fire jumps right up and gets the sticks burning. Thanks Nick



http://www.gas-turbines.com/nt6/index.html

http://www.gas-turbines.com/t98-nt-xx/index.html



Great info on turbines and how it works. I responded to how turbos work in cars and trucks. Turbos on cars and trucks do not pump exhaust back into engines. That was my point.

Thanks Nick
 
pollinator
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My instincts tell me this is a Bad idea possibly dangerous to health.
It sounds like a way of making carbon monoxide .
Not good. You cannot smell it taste it or see it but it will kill you if you are not carefull
But what do I know I only have a degree on Chemistry.

David
 
Satamax Antone
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David, everybody says it's a bad idea.
 
David Livingston
pollinator
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I know but nĂ´ one mentioned why in terms of the health of the people involved. It was all said in terms of how well the fire would burn. There are always those people who will try anything And I felt they needed to know what they risk.

David
 
Satamax Antone
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Ok Dav!
 
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sort of related. those japanese kerosene heaters manage to burn 99. 5% of the fuel. but they use forced air to do it. still need to introduce oxygen or they will use up all the oxygen in a room which is a bad thing for anyone sitting in said room that's why they have oxygen sensors fitted. i am sure if you added forced draught to a rocket you would get a better burn, but adding too much will produce Nox which is almost as bad as CO. i think trying to add the exhaust will be counter productive and cool the fire with too much nitrogen as pointed out. if they burn below the point Nox is being produced that is the maximum efficiency you are going to get out of wood without pollution from Nox

as i said kero heaters will give a bit more at the cost of electricity to run the fan and the electronics. they are great if you cant have a flue as i know from experience as they were designed for Japanese apartments where propane heaters are not allowed and modern hot water central heating is not fitted. they are used alot in narrow boats in the UK.
 
nick man
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bob golding wrote: i am sure if you added forced draught to a rocket you would get a better burn, but adding too much will produce Nox which is almost as bad as CO. i think trying to add the exhaust will be counter productive and cool the fire with too much nitrogen as pointed out. if they burn below the point Nox is being produced that is the maximum efficiency you are going to get out of wood without pollution from Nox



You are on point here. In the automotive world they run an EGR valve [exhaust gas recirculation] to help with this. At first they worked off of a check valve and engine vacuum. Later on this were controlled by the PCM. Some of the newer cars no longer use them at all. Has anyone before tried adding a O2 sensor to the flue and then use it to control a damper to limit the inlet air at the feed tube. With a car you add or reduce fuel as needed to maintain the AFR[air fuel ratio]. We cannot add or reduce fuel as needed, so maybe we can add or remove air as needed. This can help with HC and CO output. Nox is much harder. The EGR helps with that.

Thanks Nick
 
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