Does anyone know how big the combustion fan is in a corn stove?
Obviously it is dependent on the size of the unit, but I am trying to determine how big(CFM) the fan is.
I am considering building one myself, but am unsure as to what sort of airflow they are creating. I would guess it is 40-50 cfm, but would not be surprised to learn it is much higher.
I've been playing around with the same thing. I know they are using a blower to speed combustion, but I'm having trouble making it work.
I made a little burn box (2" diameter pipe, air supplied to the bottom) then I applied air to from my air compressor. I adjusted the air flow with a ball valve. Then, I attempted to light the corn with a propane torch. Regardless of the volume of air, I couldn't get it to light. Then, I took a 6" pipe and started a wood fire in it. Applied corn to the existing fire, and it burnt quite nicely.
The combustion air flue blower even in a 100,000 BTU/hr furnace is not very big. I'd guess that 50 cfm would be plenty for a corn stove, probably would need to be throttled some.
Sounds good. I was planning on throttling it via a PWM and/or some other driver circuitry. Damper doors would also work, but would be harder to control automatically.
Eventually I plan to develop a controller for this so that it is relatively automatic in regulating itself.
Does anyone have any idea where to source a small(2") auger to be used for the feed auger?
Look in the garden stuff section of a big-box store (like Homely Despot). They sell small augers for planting seeds, intended to be drill-powered. Cheap, even.
My guess is that the blower is much smaller than 40 cfm. W.W. Grainger sells a high efficentcy gas furnace that outputs 94,000 btu/ hour that has a 2 inch diameter flue.
Out here in th' PNW there's tons of 'em, cheap, if one looks around a bit. There was one in Craigslist that sold for $50 a couple weeks back. I've seen 'em free in there as well.
It took a good friend of mine 4 months to give one away. It worked perfectly. Th' guy who took it removed th' auger and other bits to build a Traeger style smoker bar-b-que.
There are quite a few manuals available in pdf form that you can download. This one is interesting, but I didn't see the CFM value listed for the combustion fan. Lots of good general info though:
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Take a look at this google search:
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I looked through a few manuals, but I didn't stubble across any CFM values. Most of them seem to use variable speed fans/controls for what it is worth...
I can't give you a good answer, however, my son is currently in the process of replacing the fan/motor in his pellet stove. The fan is a disk of approximately 6" diameter, with radial vanes on it, however, the vanes are only about 1/2 to 3/4 "wide" with a little lip on the outside edge to kind of catch and hold the air that it throws. There must be about 14 or 16 vanes. The motor is marked at
3100 rpm. However, there *is* a damper of sorts to control the amount of air that flows. The fan in on the "output" side of the fire, and draws air into the stove through about a 1-1/2" tube, then up through the fire, then into the fan chamber and finally blows the exhaust out the vent pipe. I believe it is set up this way to keep a negative pressure on the door gasket, etc. The damper is on the input side to the firebox and can throttle down the amount of air needed to make the fire burn well. Hope this helps. Ken.
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