dvawolk
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DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 17, 2013 4:56:25 GMT -8
Just to the height on the sketch. To the right only 9cm in height of ISA is blocked. The above ISA is still functional.
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Post by peterberg on Oct 17, 2013 5:22:01 GMT -8
Klemen,
Yes, I do think you are right. Your ideal chimney isn't ideal after all but if you restrict your bell size enough this would work much better. The way you do it is new to me but it looks correctly. The right side of the green strip isn't touched by the hot stream anymore, so a narrow band around the bench just above floor level won't warm up directly. Eventually it will, but only by conduction from the brickware higher up. As such, it could be a nifty way to extend your ISA, but only to be used later in the burn.
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 23, 2013 3:18:43 GMT -8
I can confirm that after a few firings it is obvious that the lower right part doesn't get direct heat from gasses... So it works as expected: cold(er) air is trapped and it eliminates some of ISA. It also provides insulation to the area below (floor). I agree that this could be easy implemented like a movable part to get larger ISA at the full burn.
I am not sure but maybe the seed of this solution was planted when Mathew described his option of rising/lowering the chimney into the bell... But this barrier is easier to implement in my case. It also works differently.
My 24 hour firings with a full batch were now repeatable successfull. So i decided to make some videos of burning... but unfortunately this filmed burning was one of the worst burnings... Based on my not so ideal chimney i suspect that at least one more insert was open, making a lesser draft for me. Also the weather was high humidity, foggy...
Anyway here is how it went:
I started a fire in a pretty much cooled stove. Exhaust was 26°C. It started well.
In the middle of prefiring the exhaust temperature reached 46°C. When mainly coals left the exhaust was 44°C.
Next video shows loading a full batchbox of dry chestnut. This was about 6.2kg of wood. It started burning right away with rockety sound as soon as i closed the door. BUT. At 1:52 you can already see flames burning backwards with a frequency...Also, soon after that the draft almost stops. This is probably stalling... Also the rocket sound ended. From previous experiences under the balcony i know that at this time whole bells are full of thick smoke. Luckily none came out of the stove...
at 2:08 i started to open door slightly. This helped a little to get at least some of rocket sound/draft.
At: 2:20 i slightly moved the wood to get a larger channel by the coals - so that air would draft by the coals to get a higher temperature and hopefully more draft... If all is okay one should rarely see the whole flame at this stage of burning. Flames are usually sucked among the wood directly to the port...
Sometimes the flames "exploded" even 15cm back out of the air intake... I think this happens at the time when the fire in the port light ups larger portion of gass... The exhaust temperature was rising veery slowly, 5 minutes into the video it was 54°C, this also shows a very slow draft... You can see some of these at 7:20. So now i had to do something and i didn't want to unload the wood and smoke the whole room. So i decided to prime a chimney with a burning newspaper, just to start a reliable draft...
After 8:45 you can see a vivid difference in burning type... A rocket launch. At that time exhaust was 56°C. At the end of video it went up to 65°C. And 7 minutes after the video 75°C. No problems of stalling after chimney priming...
Next video was started 10 minutes after the end of previous. Exhaust temperature was similar/the same. Not much to say here, it was already over the maximum of flame phase.
The last video shows the dying of flames. I also tried to show slow movement of gasses/particles in the bench, because i have glass instead of cleaning doors... I also added two mirrors inside so that i could see a flashover inside but unfortunately the sloped mirror gets lots of shes on it and i can only see slight orange light... Not what i expected... On the glass you can also see the remaining of condensed water vapours... After one burning the stove floor is dry even though at first part of burning there is condensation present... It's a lousy video...
This burn ended with maximum exhaust tempeartures of 92°C. Usually maximum exhaust temperatures are around 105°C. It is obvious why this time were slightly lower.
CONCLUSION:
- Some factors combined did a dirty job for this burning. As i don't want to rely on chimney priming i might also add another barrier to the left of the exhaust hole to get a higher exhaust temperature sooner.
- When one tries to burn a full (totally full) batch of wood in the batchbox there is some knowledge involved. If you don't have it, then it is better to stoke it half full and all should be fine.
- I think that if i would leave a larger hole above the coal and a full bathcbox maybe it won't come to stalling. Because the draft would have a direct way to the port and it would pump up the temperature because of a better burn. I just think that the batchbox was too full. Too small holes (CSA) were present among the fuel to burn properly...
- the bench is magnificent! It heats up to around 42°C when heated each 24 hours with one full batch. After 24 hours it is still warm and cosy to the touch (if not covered). The difference in temperatures at the near and far end of bench is maximally about 5°C. This should be expected with large ceiling ISA because the hot gasses are "spilled" from one end to the other end of the bench (1.3 sq. meters) and are already slightly cooled.. The bench slab with clay plaster is 13cm thick. It could be even few centimeters thicker to allow for a steadier surface temperature...We have it covered with blankets to allow slower heat dissipation (and something warm in the morning)
- as for the fuel: it is better to have more finely chopped sticks compared to thick wood. There is more surface to burn and there are more holes among them for the draft to have easier passage..
-i haven't measured exactly but based on one temperature sensor in the first part of the bell, the temperature of gasses coming under the bench slab really is around 250°C at the hottest burn... I will check this one later on... This temperature is connected to the speed of gasses.. The faster it draws, the higher (and more even) the temperature will be inside the bench...
QUESTIONS:
- because my chimney is 20 diameter and has two other inputs upstairs it is now obvious that the draft is not as good as possible... But it would be nice to know with what can i com pare this kind of chimney... The next insert is 4,5 meters from the floor level and the third is just under 7 meters from the floor level. My input is 1,7 meters from the floor leve.
So would this kind of chimney be at least simmilar to 20 diameter stack, and only 4,5 meters high?
Comments as always very welcomed!
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Post by peterberg on Oct 23, 2013 8:00:42 GMT -8
Klemen,
This stove do rely on good draft, so when the chimney is too cool the excessive production of wood gas will stall the stove. You have to watch your thermometer and don't load the firebox full when the temperature is below, say, 80 C. Loading smaller pieces won't work due to a larger burning surface and a greater production of wood gas. That strange intermittent burn is due to a lack of draft, that's all. Oh yes, when the door is open there's a greater flow of air and faster moving of the gases so the chimney temp will rise quicker.
The bench is a blind end and despite that fact it is getting warm all the way, very good! And indeed, you may have to block more of the bottom of the bell in order to reach higher temps quicker.
By the way, you have invented a way to ensure low floor temperatures. The barrier made as a sliding valve could be ideal in your situation, it could act as a bypass valve.
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Post by matthewwalker on Oct 23, 2013 9:16:44 GMT -8
Great post Klemen, thank you for sharing such detailed information. I have been burning nightly, mostly with good results, but with a few frustrating experiences as well, very similar to the burn you describe there. I have experimented enough to know that I am really putting a load on the stove by having such large metal radiators, so it's a function of me trying to run it right at the edge to see how it works, but it's reassuring to hear that you are experiencing basically the same performance as I am. I believe you have the solution to any difficult burns basically solved, and if I may offer another thought, which I'm sure you are aware of...Your mass can provide the "prime" to the chimney simply by being warm still when the next fire is lit. You may need to shorten the cycles to achieve good draft at all times, but with good knowledge of how it all performs you should be able to avoid poor burns simply by adjusting your burn schedule. Of course, there will occasionally be cold starts, but then you can prime the chimney manually. By the way, my J stove in my home, while it doesn't back puff flame like these can, does require me to manage my burns to allow the mass to prime the chimney.
I don't know about the chimney question, other than those open inlets above you are obviously having an effect. Higher temps on your end should make those less of a problem.
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 23, 2013 11:47:47 GMT -8
Hi, Peter. This 80 degrees you mentioned are based on stack performance, right? The higher the chimney/the better the draft/the lower exhaust temperatures can be tolerated?
I will think about implementing a movable barrier. It would be quite easy to implement even at this stage...
Mathew, I am aware of priming the chimney with stove itself. For me, this is significant when heating every 12 hours. I open the door for a few minutes so that warmer air comes to the chimney. Now that you mentioned it: I should expect better draft in the winter temperatures with the same exhaust temperature:-)
Also I must take care of closing the p-channel when not burning. It does draw air all the time and this is colling the mass a little faster... not that fast as with pipes, but it does disturb the otherwise "dead warm air" in a bell. Especially because it is a single bell. And first bell is not true bell...
I will check how much is exhaust temperature affected when closing the p-channel (when not burning).
For now burning twice a day comes out of question because it is still too warm outside. It became even warmer in these days, so I don't heat at all :-(...
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Post by Donkey on Oct 23, 2013 15:20:30 GMT -8
dvawolk, That barrier idea is REALLY interesting! Very clever! I wonder if it could work as plate on a rotating shaft (rotation point down at floor level).. It could rotate down to sit flat to the floor or rotate up to progressively damp bell depth.. ??
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 24, 2013 4:27:18 GMT -8
Donkey, yes i think this would be the best implementation... Especially this progressive damping is really great pros. In this way it is much more usefull compared to regular bypass.
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 24, 2013 7:11:36 GMT -8
Trying to remove even more of lower part ISA i did another version of barrier... (Attached) Attachments:
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Post by Donkey on Oct 24, 2013 16:04:58 GMT -8
Ok.. That's REALLY cool.. BUT!
I'd like to see some temperature measurements.
With and without the barrier and what it does to the temperatures below the barrier(s) and what it does above.
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aatx
New Member
Posts: 15 
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Post by aatx on Oct 24, 2013 18:03:17 GMT -8
Hi all! Since it seems like most are trying 6" models would anyone care to compare or have thoughts as to the heating load one can put on a 6" vs a 8" batchbox model? Especially in a situation like my concept here. Single bell heating tank In other experiments long ago I figured I needed 50-100,000 btu's an hour minimum. Thanks! Aaron |
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 24, 2013 21:09:21 GMT -8
I will also post the video when I start the fire. I have cleaning door closed with a glass and with this kind of barrier it will be below the gas barrier. Gases are seen in the first part of burning. I will also add the thermometer in this lower part of the bell.
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aatx
New Member
Posts: 15
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Post by aatx on Oct 25, 2013 8:36:26 GMT -8
On page 1 there you have this layout, very helpful, one note, the sketch for the 187mm (7.4") bricks 230x114x76mm the conversion to inches is quite off and had me thinking it was sized very different than your metric numbers actually say. When I convert mm to inches I get 9.05x4.48x2.99(close to 3) Perhaps the 0 is missing from 9.5, 5 was swapped for the 4 in 5.5? |
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Post by Donkey on Oct 27, 2013 15:33:01 GMT -8
Yer 187mm model does not appear to be there..
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Oct 28, 2013 0:11:50 GMT -8
On page 1 there you have this layout, very helpful, one note, the sketch for the 187mm (7.4") bricks 230x114x76mm the conversion to inches is quite off and had me thinking it was sized very different than your metric numbers actually say. When I convert mm to inches I get 9.05x4.48x2.99(close to 3) Perhaps the 0 is missing from 9.5, 5 was swapped for the 4 in 5.5? Ok... This was a lousy mistake. Editting now... Also, regarding those first post links etc, i will be making some editting to be a more helpful text. The most certain system is to make a calculations for the exact mathematic measures and then try to build something very similar with your brick dimensions... The calculations can be done with excel spreadsheet (i think it should be somewhere on the forum). The equations are written in first part of this thread, also... I will compile the info i gathered from forum and my work of this batchbox. It should be a good how to for a first starter... |
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