mechanical energy from boiler

mark123 Posted By mark123, Apr 7, 2018 at 5:13 PM

  1. mark123

    mark123
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    I have a Woodgun E180 and have learned to live with the chugging or huffing whatever you call it when burning very dry wood. It is a normal part of my burning now, I dont pay any attention to it anymore. I was just thinking why not have a large diameter short stroke piston of sorts in a wall of the firebox connected to a crankshaft and flywheel and take advantage of these "explosions". I would guess frequency at approx 3 per second. my boiler weighs 2700lb and shakes (slightly) to this so there must be some significant energy there. It has been doing this since day 1 and I tried everthing to stop it but at the end of the day it doesnt hurt anything and heats the house perfectly so I just let it do it's thing.
     
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  2. DoubleB

    DoubleB
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    Yikes I can't imagine that's good. I'm no expert on your boiler but something sounds seriously wrong. I wouldn't worry about capturing mechanical energy from a problem, I would figure out what's wrong and address it.

    If this huffing is frequent and big enough to make any meaningful mechanical energy in equipment meant to be static, then that sounds like a recipe for a big problem on your hands.

    As for your question, if generating mechanical energy is your objective, there are probably better ways to do it. Heck, it'd probably be easier/safer/more reliable/more power to run some pipes through your boiler to generate steam for a steam piston, and I am not advocating that.
     
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  3. leon

    leon
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    If you can post a picture of your set up please your boiler should not do that period.

    You may be making steam and not realizing it and if the blow off valve is not working
    all that energy you are making with the firewood is a recipe for trouble and a boiler explosion.
     
  4. mark123

    mark123
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    My problem is my boiler room /wood room gets up to 95F and the wood is super dry. They have a video explaining the phenomenon, they call it back puffing.
     
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  5. brenndatomu

    brenndatomu
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    They don't offer a solution for you? (I didn't watch the video, due to limited internet data)
     
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  6. DoubleB

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    Yea, it appears the purpose of the video is to describe how to fix the problem. I don't know it it's the best series of solutions, but it's clear the puffing is not desired.

    And, back to the original question, certainly not a good way to make mechanical energy by exploding the smoke.
     
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  7. brenndatomu

    brenndatomu
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    Very true...even in an internal combustion engine the fuel ignites and expands in a very controlled manner...not an "explosion". When things go wrong and you start having "explosions" in an ICE...things start to break pretty quickly...
     
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  8. leon

    leon
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    Some video!;

    What you need is more combustion air and a smaller fire, you have to provide a source for external air to enter your boiler room.

    Many folks just pipe in fresh air from the outside by running PVC pipe from the outside using a 90 degree fitting and a slotted drain cap over the short piece of PVC pipe facing downward.

    Some folks just attach a dryer vent in the wall or run the PVC pipe along the ceiling joists down to the boiler and terminating it near the boiler air inlet.

    I have had flame throwers coming out of the upper or lower air inlet doors of my old boiler many times due to the lack of combustion air/draft at times.
     
  9. mark123

    mark123
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    They do make some add on solutions that appatently help but like I said it doesn't bother anything and works fine for the past 7 years this way. Nothing to do with combustion air, I have 6" pvc outside air intake. Actually if I disconnect the air inlet it calms down a bit. I am thinking the mass of the air in the long intake amplifies the problem, all that air in the sealed pipe going back and forth...there is a garage door right beside the pipe as well and with it open and air inlet pipe disconnected it still occurs just not as bad.
     

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  10. salecker

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    I find my Econoburn does that as well with extremely dry wood in small splits.Bigger splits or rounds don't have the same issues.I feel that the spruce we have up here burns different than the hardwood the boiler was designed to burn.
    Some year when i have nothing to do i may experiment to see if there is any way to tune my boiler better for our wood.
     
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  11. Marshy

    Marshy
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    I would not advise you trying to use your boiler for such an experiment. However, what's happening is easily explained. The wood is off-gassing combustible gasses which saturate the firebox until it ignites. A small subsonic explosion occurs when ignited called defligration. It could have the potential to cause damage so correcting the issue should be considered.

    That being said, you can use the combustible gasses from wood smoke to power 4 cycle internal combustion engines through gassification. Lots motor vehicles have been retrofitted to run on wood gassification.
     
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  12. Karl_northwind

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    you can reduce your primary air. I think it comes in in the top right and left corners at the front of the upper chamber. maybe put a strong magnet halfway over the opening in the burn chamber. if that doesn't help, you could take it off easy.
    maybe soak some of your wood in water for a half hour before putting it in the boiler? :)
     
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  13. coaly

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    A piston, crankshaft and flywheel requires the admission of steam, high pressure air or vacuum at precise timing intervals. Just like an internal combustion engine, the timing of the spark to ignite the fuel must be accurate and changes with engine speed.
    Unlike internal combustion engines a steam engine has constant pressure at the throttle which is a type of steam valve and the incoming steam comes into the cylinder through a steam valve controlled by the eccentric rod connected to crankshaft similar to a cam shaft controlling the valves in an internal combustion engine. Valve opening and closing adjustment is called "cut off" since we adjust the timing of valve motion which is mechanically operated by the eccentric rod. Full power would open intake valve for the entire stroke so you have steam pressure being admitted into cylinder the entire length of stroke. The back side of piston is the same way, so we are always under power moving the piston in the opposite direction. The faster the RPM, the more energy built up by the flywheel (or locomotive wheels) so you adjust the valve to a shorter stroke to allow less steam in, saving steam and taking advantage of the expansive nature of the steam through the entire stroke. Hence the terminology "cutting off the steam" for higher efficiency. So although the sound is similar to the exhaust of an external combustion engine, it's far more complicated than that.

    Your pressure differential would control a diaphragm of sorts connected to a piston (pump side) for liquid or air. This is how a steam pump works with a steam piston that moves a pump piston. No converting energy to rotating with a crankshaft. It can move back and forth with the pressures provided at will without timing issues using a crankshaft and flywheel for a constant stroke length. (that was James Watt's invention along with the fly ball governor) You would think positive pressure moving a diaphragm or piston would create more power than negative pressure, but the negative pressure side of a hot air engine creates more power than the pressure side. The piston is moved by expanding air on one stroke and by cooling the hot air in a chamber (they were used for water pumps using the cold water being pumped for cooling) creating a vacuum. The low pressure side is the stronger power stroke than the high pressure side.
    These are the kinds of engines I work on. Obviously I was born 100 years late.

    Since I work on the boilers that supply steam to the engines, some get the flutter you're experiencing with so much out gassing the flame burns up the available oxygen and dies, ignites and dies over and over. Crashing the wood down in a wood firebox helps. Having some wet coal handy, usually big chunks of Bituminous stops it as well. I call the faster huffing a flutter since back puffing is a much slower rate. That can be caused by a cooling stack that allows colder air to drop down as the draft stalls on stationary boilers. As flue gasses keep rising and falling, it eventually allows oxygen into the firebox from the stack where it feeds the fire with a back puff and starts chuffing. That's when you have to turn on the blower and open the air to get the flow in the right direction even if you don't need to make steam. Then let it blow off and ignore the looks from over firing...... it's all about anticipating the engineers needs when firing, but the engine operator can always have an emergency or shut down for some reason leaving you hung out there.
     
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  14. TCaldwell

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    Correct me if I’m wrong but the wood gun maybe a gasification boiler but doesn’t have a independent secondary air source that would certainly help controlling the chugging.
     
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  15. Chris Hoskin

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    one of the things we talk about with Lambda controlled boilers is that they work better with higher moisture content wood. Wet wood is much more common a problem than too dry wood in my experience !!! However, the o2 sensor also helps a boiler burn better with especially dry wood. Think of it like electronic fuel injection - always optimizing the fuel/air ratio.
     
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  16. brenndatomu

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    Really? Why is that?
    I have heard this before, but really couldn't find much data to back that up other than a research project done on a large bio-mass boiler...and even then there was only a small increase in efficiency over a narrow MC range.
     
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  17. TCaldwell

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    That’s true, with higher mc wood the lambda controller forces the combustion by increasing the primary air/ decreasing the secondary air to maintain a higher combustion temp. Likewise with very dry wood the control retards the fire with the opposite air settings than above. It’s been my experience that forcing rather than retarding is more successful from a control standpoint, and possibly from a efficiency standpoint as well.
     
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  18. Chris Hoskin

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    Yep, what TCaldwell said.

    Also, just to be clear, I'm not saying a lambda boiler can burn green wood effectively - just that if your wood is 25% instead of 18% the lambda is going to do better than the non-lambda boiler.
     
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  19. brenndatomu

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    Ah, gotcha. I misunderstood what you were saying then
     
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  20. Marshy

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    That is good news because my wood is typically no less than 20-22%. I don't store it under a roof or in a shed for 24 months like some do. I leave it seasoning in open rows from early spring to winter, only covering it in late summer before the rain season. This is effective with most hard woods except oak. Splits are no larger than 3" on the thickest edge. Sounds like there is some interesting research to be had based on this discussion.
     
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