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Post by peterberg on Sept 19, 2021 1:57:25 GMT -8
I like my designs tight, that's true. One can't change the tested design and expect the core to behave exactly the same as in the original configuration. The exit hole is to the side instead of the top front and there's no sign of a stumbler's block either.
The foor channel's stub seems to strangely pointing to the side instead of to the port itself. And I am unable to see whether or not the riser stub is according to specs.
In general, there seems to be two possible restriction points which are throwing up problems. The first being the transition from main bell to the bench. This should as wide as possible, meaning all the available space. As wide and high as the bench is internally. And the exit to the chimney should be low in the bench and at least 150% of the system's cross section area, preferably more.
By having a good look at your pictures I suspect there's another restriction area as well, being tunnels in the bench. Those aren't smooth at all by the look of it, plus there are almost certainly a couple of 90 degree bends and maybe a 180 degree turn as well. Let me guess: you used the recommended ISA of a bell and converted that 1 to 1 to a piped bench? If that's the case, this is where the main restriction area is in this configuration. Severe shortening of the bench is in order then, smoothing the walls and widening the bends perhaps as well. The magnetite bricks aren't helping here, those are gobbling up much more heat as compared to normal red bricks. Making the recommended ISA values worthless here.
Sorry.
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Post by Orange on Sept 19, 2021 4:32:57 GMT -8
thanks guys, I've removed the wall in the second bell that was a restriction and it added to ISA:  red part was removed: 
so now it looks like this:
seems to be working well. Even got some nice discoloration:
as outside temps were still like in Summer (20C+) I'll need to test it when it gets cold.
only issue now is some bad smell above the first bell when fully heated - my suspects are CFB, old cast iron coating or air-concrete insulation (multipor) around the firebox. I think by the smell it can be air-concrete.
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Post by Orange on Sept 19, 2021 6:02:19 GMT -8
It looks like a small fire in a large firebox, which most designs don't cope with well. Without the secondary combustion it cant burn clean, and without a fire big enough and hot enough to heat the firebox up properly it wont burn off any soot from startup on the ceiling. Only thing I can see in the mass that maybe could cause a problem is all those vertical ridges down the sides, that would increase the surface area but also create drag. Hope you can get it running right. yep, removing that wall inside bell and lightning bigger fire helped! - primary air frame: I used 50mmx50mm square tubes for the frame (30x44 openings). For your 170mm design, I understood that you use 60x40 tubes. May be you do not allow enough primary air inside your firebox. For my next design (200mm riser) I scaled it to 80x50. - coating: I just put oil the frame and it protects quite well against corrosion but not against water coming from condensates. The top window and its frame are a cold source. I get condensation there, inside the stove when smoke temp is too low. Water is then dripping along the steel and corroding the whole inner side of the frame. - air frame: yes, I didn't want a huge frame so I put smaller 60x40x3mm tubes. CSA-wise air should be ok, there's only one small restriction like 1cm from bottom air inlets. And doors are not airtight, intrerestingly heater can run with all doors closed - coating: I'm considering your option or coat it with waterglass. Or maybe leave bare metal. Hope you get your heater running right. Orange, insulate that chimney. That would be the first step i would take on a lazy burner. And, check and recheck for constrictions. I bet there is something you overlooked, which is restricting your draft. - yea without that bell wall I'm getting easy over 100C in a chimney. Might still insulate that spiral ventilation pipes, I've heard they can break in case of chimney fire. -exit port is enlarged, it's now greater than system size CSA. But wasn't enough I had to demolish wall in the bell too. The exit hole is to the side instead of the top front and there's no sign of a stumbler's block either. The foor channel's stub seems to strangely pointing to the side instead of to the port itself. And I am unable to see whether or not the riser stub is according to specs. You got an eye for details  - floor channel is according to specs, I'm just missing a piece of iron on top of the riser stub
- removing that wall inside the 2nd bell helped a lot - I've got the stumbler so the only difference is exit to the side (like on batchblock), here's the current situation: |
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Post by pianomark on Sept 19, 2021 12:23:31 GMT -8
"only issue now is some bad smell above the first bell..."
Ceramic fiber board will smell bad until all the binder used in it's manufacture is burned out. Burn it hot on a cold day, and open all the wndows!
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Post by Orange on Sept 26, 2021 8:44:36 GMT -8
the thing still isn't working right - with bypass open chimney temps go to 150-200C but when I close it it quickly goes down to less than 50C and fire dies out. And it's still summer temperatures outside (24C). so the 2nd bell needs more destruction: In general, there seems to be two possible restriction points which are throwing up problems. The first being the transition from main bell to the bench. This should as wide as possible, meaning all the available space. As wide and high as the bench is internally. And the exit to the chimney should be low in the bench and at least 150% of the system's cross section area, preferably more. I'm suprised how other stoves (for example Vortex) work when gasses flow trough small tunnels, bends and lots of mass. In my bench many bricks are hollow to it's not that much mass. Also firebox is low mass.
original plan was to force gasses to the front of the bench where heat is needed the most but with the bad draw this wall will be destroyed:    gass path from 1st bell trough 2nd bell:
 this is situation after more dectruction, hopefully I won't have to enlarge that exit to chimney, we'll see:
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Post by fiedia on Sept 26, 2021 10:26:47 GMT -8
Surprising, did you try to close your bypass gradually. The whole thing may need some time to warm up before closing totally.
Is it cooler inside your house than outside ? If the bench temp is at 20°C vs 24°C outside, it is impossible to get good draft.
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Post by Orange on Sept 28, 2021 0:43:54 GMT -8
Surprising, did you try to close your bypass gradually. The whole thing may need some time to warm up before closing totally.
Is it cooler inside your house than outside ? If the bench temp is at 20°C vs 24°C outside, it is impossible to get good draft.
- I didn't close it gradually since it's only 1/3 of sytem CSA.
- that's interesting, I guess it's a bit hotter outside
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Post by Vortex on Sept 28, 2021 1:59:31 GMT -8
How long is the chimney, is it all uninsulated galvanized ducting, is it inside a masonry chimney or in open room, and does it have any bends or chimney cap/cowl or similar?
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Post by Orange on Sept 28, 2021 6:07:02 GMT -8
chimney is from bottom to top: 2m of thin galvanized pipe (170mm diameter), inside room, slight bend 2.5m refractory pipe(200mm diameter) inside hollow clay brick, inside room, no bends 1.5m refractory pipe(180mm diameter) inside hollow concrete, outside on the roof, no bends, with concrete cap on top  
so it's not insulated but it's not terrible, worked flawlessly with basic metal stove.
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Post by martyn on Sept 28, 2021 7:29:54 GMT -8
titanium exhaust wrap Would be a quite cheap method to insulate the lower part of your chimney, looks great too…..
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Post by Orange on Oct 4, 2021 10:22:43 GMT -8
fiedia closing bypass gradually helps!
stove runs well but for first like 15min door has to be open so there's enough air for the fire because chimney draw isn't established, and then some smoke comes out of front:
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Post by satamax on Oct 4, 2021 20:49:01 GMT -8
Well, it is rocketing. The smoking back is normal at startup i think. Plus you're burning pine. This is how i light my latest batch. It's been running for 5 years. I make a tower of criss cross kindling, with several pieces on top, and paper underneath, in front of the port Light it, and let it burn nearly all. Then put long kindling and stuff like your 60*40mm you have in your video above, no more than 1/3rd of the firebox. let that burn a bit. When the ends towards the port are fully in flames, i put the big bits on top. Fist size or more. Then, let that burn to the embers, before i reload. www.youtube.com/watch?v=3BhiWO0078UI have smokeback at startup. But i haven't cleaned the first bend last year nor this year, it might be full of fly ash. I need to look. |
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Post by satamax on Oct 4, 2021 21:02:25 GMT -8
With all the modifications you have done, it sounds all right now. But is it is not working well, when the mass is hot, and outside temps have cooled down, i guess the culprit could be where you have 1.4 csa. I would move that wall towards where you have 9x csa, you don't need as much there. To enlarge the chimney inlet. That is if ever you rebuild around that part. I would go may be 50mm lower, but much wider. What do you have now? something like 30 cm wide by 20 tall? A trick would be to free the "wall" side of your chimney inlet; imagine if you're looking from above, only one side of the square is open, for the moment, where you have 1.4 csa. I would try to free the side against that middle brick wall. Well, i hope you get what i am saying. |
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Forsythe
Full Member
Instauratur Ruinae
Posts: 208
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Post by Forsythe on Oct 5, 2021 0:29:00 GMT -8
titanium exhaust wrap Would be a quite cheap method to insulate the lower part of your chimney, looks great too….. Agreed, this is a really cool setup, and I can’t wait to see this thing running right for you, Orange. That exhaust wrap is a great idea from Martyn — to add on his idea: maybe use the exhaust wrap directly around that galv. pipe *above* the height of the burner unit… but: leave the air gap open between the back of the DSR’s rear wall, and insulate the sides and around the back of the pipe in that area. Idea being: you probably don’t want to thermally isolate the lowest part of the exposed stovepipe behind the firebox from any heat which the firebox might be emitting from its rear face. Insulating around the both of them together should help to reuse that heat and promote draft. [in theory]  |
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Post by satamax on Oct 5, 2021 9:41:59 GMT -8
Well, i wanted to show you a healthy startup.
In that one, it smokes back a smidge. I have to close the door.
Then, in the following one. Once you start to fill up the firebox, it draws soo much, that smokeback isn't much of a problem anymore.
Even pulsating, it doesn't smoke back.
Outside temp, 7.3c° 95rh raining.
Inside temp, 20.3c° and mass, which should be equalised between inside and outside after 18/20 hours of not burning, 32c°
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