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Post by masonryrocketstove on Nov 30, 2023 5:47:33 GMT -8
I’m pretty sure he means “stale” as in: the smoke is forming in the front of the firebox and that air isn’t being drawn through the port into afterburner at a fast enough rate, so that pocket of gasses kinda hangs there, without being replaced by incoming air. Maybe “stale air” is an American English term we use for air that isn’t moving and being replaced by fresh air?
But yeah, I would think Trev’s right, and that’s probably caused by too much resistance in the top chamber, which would reduce the rate of draw/suction on the firebox.. and could prevent that pocket of stale gasses / smoke in the front of the firebox from being pulled through the port, getting mixed with combustion air, and burning off rapidly enough.
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jonasp
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Post by jonasp on Nov 30, 2023 6:27:15 GMT -8
I’m pretty sure he means “stale” as in: the smoke is forming in the front of the firebox and that air isn’t being drawn through the port into afterburner at a fast enough rate, so that pocket of gasses kinda hangs there, without being replaced by incoming air. Maybe “stale air” is an American English term we use for air that isn’t moving and being replaced by fresh air? But yeah, I would think Trev’s right, and that’s probably caused by too much resistance in the top chamber, which would reduce the rate of draw/suction on the firebox.. and could prevent that pocket of stale gasses / smoke in the front of the firebox from being pulled through the port, getting mixed with combustion air, and burning off rapidly enough. My english is not the best but yes exactly what you written down. The top chamber resistance is ok i think and I'm afraid if i reduce the resistance it'll overfuel even more I get pretty much a full vortex when it get's going.  Here are 3 movies, right before the peak, peak with overfuel, opened the primary air more and after some time the overfueling almost completely stops and get's back to stable. drive.google.com/file/d/1pwu1gX3UMXTmtWaJcP2coyt4xH03SCJQ/view?usp=sharingdrive.google.com/file/d/186P41m4gldLYFIBV5gL0UGoKsMY5Tcgj/view?usp=sharingdrive.google.com/file/d/1ZTKpPs7srfwk9VIdJ7E6SZpVjlY81UZC/view?usp=sharingToday when it overfueled it took longer to calm down. It does calm down when i open the door a bit more. |
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Post by masonryrocketstove on Nov 30, 2023 7:46:30 GMT -8
Is your door completely tight-fitting? Trev discovered along the way that a door with a millimeter or two of gap between it and the frame seems to make it run best. Maybe the seepage of combustion air along the top of the door gap would clear away that pocket of stale gasses and smoke at the front of the firebox? Just an additional guess, since you mentioned that opening the door a crack will clear the smoke..
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jonasp
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Post by jonasp on Dec 1, 2023 0:18:46 GMT -8
Is your door completely tight-fitting? Trev discovered along the way that a door with a millimeter or two of gap between it and the frame seems to make it run best. Maybe the seepage of combustion air along the top of the door gap would clear away that pocket of stale gasses and smoke at the front of the firebox? Just an additional guess, since you mentioned that opening the door a crack will clear the smoke.. Yes it's tightly fit. Today I removed part of the fitting rope on the top side of the door and so far no overfueling at the peak. I'll try this setup a few more times to see if that'll actually solve the issue. Maybe it kinda acts a bit like secondary air since it flows under the ceiling of the firebox towards the exit? |
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Post by Vortex on Dec 1, 2023 4:06:56 GMT -8
jonasp Sorry for the slow reply, very busy here at the moment. If I increase the resistance in my top chamber too much or reduce the size of the port and or afterburner, then those are the same symptoms I get - I know it seems counter intuitive. When you get the balance of resistance and primary air right it's surprising how little air it wants. Remember any extra air just carries heat through the mass and out the chimney. The vortex in your videos looks too slow and too dark red, that will show higher CO. you want to aim for a faster spinning vortex, more golden orange in color. Trev
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jonasp
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Post by jonasp on Dec 1, 2023 5:21:08 GMT -8
jonasp Sorry for the slow reply, very busy here at the moment. If I increase the resistance in my top chamber too much or reduce the size of the port and or afterburner, then those are the same symptoms I get - I know it seems counter intuitive. When you get the balance of resistance and primary air right it's surprising how little air it wants. Remember any extra air just carries heat through the mass and out the chimney. The vortex in your videos looks too slow and too dark red, that will show higher CO. you want to aim for a faster spinning vortex, more golden orange in color. Trev No worry, i appreciate every response even if it's days/weeks later! It does feel counter intuitive. I'll reduce the resistance of the top chamber and see how that goes. I'll keep this up to date. Thanks again! |
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jonasp
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Post by jonasp on Dec 2, 2023 1:54:09 GMT -8
Today I reduced the resistance by removing 1 vermiculite plate on the shelf. The vortex was going faster and just licks the end of the shelf. Unfortunately at the peak the overfuel is much worse this burn and takes way longer to get back to stable. Not sure what my next steps could be to get it more stable
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jonasp
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Post by jonasp on Dec 2, 2023 2:07:47 GMT -8
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Post by Vortex on Dec 2, 2023 5:36:14 GMT -8
The vortex and color look much better now, but she's still overfueling a little.
One thing I notice is the whole stack is burning from top to bottom, it should just be burning from the top. Are you lighting on top? Stack the timber quite tightly with a large piece in the bottom of the V then gradually getting smaller in size towards the top.
How much primary air are you starting off with? There's an optimum level that if you go over will encourage overfueling. It's about 15% csa on mine. If it's more try less and see how it goes.
Trev
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jonasp
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Post by jonasp on Dec 2, 2023 8:09:19 GMT -8
The vortex and color look much better now, but she's still overfueling a little. One thing I notice is the whole stack is burning from top to bottom, it should just be burning from the top. Are you lighting on top? Stack the timber quite tightly with a large piece in the bottom of the V then gradually getting smaller in size towards the top. How much primary air are you starting off with? There's an optimum level that if you go over will encourage overfueling. It's about 15% csa on mine. If it's more try less and see how it goes. Trev I stack from bottom to top and light on top just under the exit port but honestly I should use more thicker logs for the bottom. At the moment I use round logs which does create more gaps so the fire will spread faster to the bottom. I don't know exactly my primary air csa since I'm not sure how much % the grid inside the primary air opening let's air through. If I fully open it my guess would be around 30 csa. It's definitely been running more than 15%. Tomorrow I'll try from the start with less primary air and keep you guys updated |
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jonasp
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Post by jonasp on Dec 3, 2023 5:45:10 GMT -8
Another day, another burn. Fire started a bit too slow, probably need more kindlings with these cold temperatures.. I set the primary air to 15% CSA to start which worked well. After a while the vortex was more struggling to fully form so I opened air to around 20% CSA. The whole burn was pretty stable but at 1 point it almost overfueled. If you watch carefully you can see it almost overfueling but it luckily did not. drive.google.com/file/d/1GMkfCBGIwdGfQHKvP9ryLrHv-QObaflY/view?usp=drivesdkThis is probably one of the more stable stable runs I've had so far. Do you also start at 15% CSA primary and do you later adjust that? If yes at what point do you open it more? |
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Post by Vortex on Dec 3, 2023 11:30:19 GMT -8
That's looking better jonasp. Your top chamber glass is a little difficult to see through clearly, but it looks like you have enough primary air - remember a palm tree shaped incomplete vortex is a sign of too much primary air. A vortex that fills the afterburner and streams out around the top chamber is too little. Do you still have the door seal removed from the top of the door? That would be allowing more air in, (I only used secondary around the door edges on my original stove). 15-20% primary is the most I use, and only up to the peak of the burn, then I reduce it to whatever keeps the vortex well formed.
If your startup is a little too slow try a bit more kindling next time. The combustion rate of the timber looks better this time, it's very much an aspect of the amount of exposed surface area of the timber, the looser it's stacked the faster it'll burn, tighter slower.
Play with those variables, including maybe adding back a little more resistance to the top chamber and you'll gradually get the feel for it.
Trev
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jonasp
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Post by jonasp on Dec 4, 2023 0:15:38 GMT -8
The vortex glass does get a white gaze on it. I did seal it back to have less parameters to figure out. Today I had a great start but later on it struggled to keep the full vortex going. It wasn't palm tree shape but just incomplete and not fast enough vortex. Reducing primary air didn't help, i had it running at roughly 15% the whole time, 10% not much change in vortex either. Tried opening it more to 20% but not much of effect, little bit worse even. Above my white oven I have another restriction, I don't remember exactly how much CSA that is but it's definitely over a 100% CSA (my guess would be 120%), could this be the issue of sometimes struggling vortex or is it more likely the chimney and outside temperatures? (0degrees celsius) In this post you can see my airflow after the afterburner donkey32.proboards.com/post/38613/threadAnd in this post how i implemented the restriction donkey32.proboards.com/post/38726/thread |
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Post by Vortex on Dec 4, 2023 10:12:16 GMT -8
The haze on the afterburner glass is fly-ash, it just wipes off with a damp cloth. The cold outside temps should improve the draw not lessen it.
If the vortex is too slow then you probably still have a little too much resistance. Can you enlarge the top chamber exit a little, it could be a little tight with those steps so close. More square exit seemed better for some reason, but I can see you have similar constraints to me there.
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jonasp
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Post by jonasp on Dec 5, 2023 2:14:28 GMT -8
Today i had an overfueling situation again.
I've checked again all the dimensions on my 3D files, compared it with your sketchup design(scaled it up).
My top chamber seems to be with 2 vermiculites shelfs 90% CSA and with only 1 shelf it's 120% CSA I'll try to make it so it's 100% CSA which is what your system is.
My space after the afterburner and top chamber seems to be bigger in volume.
Maybe my system is not running smooth and stable since the dimensions is a bit different in the amount the gasses are allowed to expand after the vortex and then getting restricted again by the top chamber.
I've read somewhere in the DSR3 design it's very important the ratio between gasses being expanded and getting restricted again.
I'll measure again the exact dimensions inside the stove when it's cooled down and make some changes.
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