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Post by patamos on Feb 13, 2019 11:02:03 GMT -8
Hi Trev, Ya good to be back. The kiln shelves hold up really well. My potter friends have been using them in kilns for I-don't-know-how-many-firings at 1200c+ temps. Eventually they may crack but they are more likely to cone/warp from super high temps. I have been installing reclaimed 1" thick ones as firebox roof with no problems so far. Of course i make sure they are loose fit so they can expand without perimeter point loads.
From what you and Matt are saying about CFB, my experiments in coating them create more of a problem than solution.
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Post by coastalrocketeer on Feb 27, 2019 13:36:52 GMT -8
Hey WJ... hope all is well with you. Have you had any more chance to try this system out?
One Q I had... is there no secondary air in this system? I may have missed hat info in the thread. If so, sorry to ask the already answered.
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Post by wiscojames on Feb 27, 2019 18:58:50 GMT -8
Every chance I get. I'd say 10 times. Mostly scrap pine lumber, though I've tried the wax/sawdust firelogs, as well a mixture of pellets and scrap lumber. The firelogs burned longer and slower, with lower peak temperatures and less flame show. Less mixing, too, I suppose. Less complete combustion? Pellets also worked well, particularly combined with the pine. Which brings me to secondary air. Sheer laziness caused me to not implement it. It's on my list, though. With whatever fuel, the setup seems pretty effective at heating up the appx 1800 pounds of mass. There's a griddle on top that I really need to start cooking on.
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Post by wiscojames on Feb 27, 2019 19:00:50 GMT -8
PS- Still using a booster fan, due to the uninsulated, outdoor chimney.
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Post by coastalrocketeer on Feb 27, 2019 21:50:58 GMT -8
Thanks for the answer and update!
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Post by wiscojames on Feb 28, 2019 12:40:28 GMT -8
Here at the WJ test bed in the greenhouse I inserted a donut of leftover 1" ceramic fiber around the port, conforming to the cylinder. I thought it might increase dwell time, and more importantly to me, might straighten out the flame. (The cuts that make the port are nowhere near perpendicular to the cylinders.) Strangely, I think it may have straightened it out some. I'll let more knowledgeable folks to judge the nature and quality of the flame. drive.google.com/file/d/17i6WBM_0Ak8PSie2UHA60i13G49EIneN/view?usp=drivesdk
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Post by Vortex on Feb 28, 2019 13:21:42 GMT -8
Nice fire fountain. A 2 inch deep port will keep it a lot straighter than a 1. As flame can enter a 1 inch deep port at a 45 degree angle and go straight through, whereas with a 2 inch deep port it would hit the side and get straightened up. Sounds like you've got munchkins in your greenhouse
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Post by coastalrocketeer on Feb 28, 2019 13:32:22 GMT -8
Interesting... might just be the lighting conditions/camera settings but it looks more yellow and less orange.
How about a test with that baffle around the sides and top with the bottom open? Interested to see if there is a positive or negative difference.
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Post by DCish on Feb 28, 2019 13:40:56 GMT -8
Here at the WJ test bed in the greenhouse (punny, right?) I inserted a donut of leftover 1" ceramic fiber around the port, conforming to the cylinder. I thought it might increase dwell time, and more importantly to me, might straighten out the flame. (The cuts that make the port are nowhere near perpendicular to the cylinders.) Strangely, I think it may have straightened it out some. I'll let more knowledgeable folks to judge the nature and quality of the flame. drive.google.com/file/d/17i6WBM_0Ak8PSie2UHA60i13G49EIneN/view?usp=drivesdkI wouldn't necessarily expect any increased dwell from that addition. For dwell to increase, there would have to be some sort of space to fill with flame, then some sort mechanism that encouraged the gases to circulate within that space. Your addition reduces the space available for dwell in that spot, which I would expect to encourage more direct flow-through. As near as I can tell so far, increased dwell is encouraged by having a somewhat larger space followed by some form of restriction. If it is a straight pass-through space, there is no increase to dwell until flow rate increases to a point where the restriction creates back-pressure, causing flame to back up and "wander around" the space on the way to the exit. Imagine a bucket with a 2" hole being filled from a bucket with a 1" hole -- if you aim right, the second bucket never fills at all, the water flows directly through. Aim wrong and there is some splashing around, but no accumulation to speak of. Now picture that bucket with the 2" hole being filled by a bucket with a 3" hole. Aim the stream perfectly at the hole, and there is still too much flow to pass through all at once, so the second bucket begins to fill with swirling water. Plan the flow just right, and you have a bucket full of swirling water. The second scenario where I have seen dwell increased is with the the creation of a vortex that sends the gases spinning around inside a space. When there is no restriction afterward, it seems to spiral rather quickly onward, but the circular path still takes longer to traverse than the direct pass-through. When flow is high, the space is slightly larger than system size, and especially when there is a nominal restriction following, I have seen concentric vortices appear, something I interpret as an indicator of increased dwell time. Is increased dwell good for anything? I hypothesize that it is, but with the caveat that I don't have the equipment to be able to test this just yet.
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Post by wiscojames on Feb 28, 2019 14:02:51 GMT -8
Vortex - Good catch on the munchkins. I should ask for them to play the ukulele in the background next time, instead of making strange noises.
The port has always been 2" - two thicknesses of ceramic fiber, one in each cylinder. But something about that scrap seems to have changed the flame path. It's closer to vertical, and more chaotic - less 'fluid'.
Coastal - the door is pretty tight. If you look, you'll see I have the top edge propped open about a half inch. That seems to be the sweet spot. It'll pulse at the height of the burn if that gap is too small. If it's wide open, the flames in the top thin out a bit.
DC - I hear what you're saying on dwell time. I misused that term, I guess. A more chaotic flame pattern is more accurate. I'll need to capture it next time, but fwiw, if I close the door altogether at the height of the burn (gaps feeding oxygen), it seems to slow the speed and the top cylinder is filled with flame front to back, with some flames reaching past the cylinder's exhaust to the small half barrel above. In that case I might be approaching a vortex-like pattern that is slowing things a bit.
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Post by Vortex on Feb 28, 2019 14:48:59 GMT -8
Oh, I see now that the new piece of ceramic blanket is a big circle shape. I thought it was a circle with the port hole cut out of the middle, thus making the port deeper. So yes that is odd that it's straightened it up... A deeper port will keep it straighter, but of course anything cut through ceramic blanket is going to be a bit vague. In your video the fire fountain looks like it's rushing to the exit faster than before. I would try making a restriction around the inside edge, like Brian did on his and I did on mine with a thin strip of ceramic blanket, that seems to help: www.vftshop.com/images/others/Stove/restriction.JPGAlso If the exit hole in the roof of the top chamber is 1 CSA or more, I would try reducing it to somewhere around 80% CSA and see how that affects it. And of course more musical munchkins
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Post by DCish on Mar 1, 2019 18:08:22 GMT -8
I'll need to capture it next time, but fwiw, if I close the door altogether at the height of the burn (gaps feeding oxygen), it seems to slow the speed and the top cylinder is filled with flame front to back, with some flames reaching past the cylinder's exhaust to the small half barrel above. In that case I might be approaching a vortex-like pattern that is slowing things a bit. Cool, I'd love to see that if you are able to catch it! I get the same thing in the main chamber of my box stove if I cut the air back at the very top of the burn, but I haven't had a tight enough build to approach it in my backyard experiments.
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Post by wiscojames on Mar 2, 2019 5:36:59 GMT -8
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Post by gadget on Mar 2, 2019 6:40:51 GMT -8
Has anyone seen any signs of erosion using blanket for the port? Rounding of the edges over time? I have heard that the blanket becomes more rigid as it is fired.
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Post by DCish on Mar 2, 2019 6:49:45 GMT -8
Nifty! Looks almost like the open-door condition has lots of excess air over-cooling the flame, and the closed door allows it to really take off.
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