dvawolk
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DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Feb 2, 2013 0:13:46 GMT -8
Yesterday i did another test with it.
SPECS: 6" system batchbox horizontal feed with p-channel and closed front doors (with primary air intake at the bottom of the doors opened to about 40-50 sq.cm...
This is how it went:
16:50 The stove was cold and humid due to below zero degree in the mornings. I started a fire with some kindling just behind the port and then added smaller wood pieces (about 2 cm across) on it and above those larger ones (over 6 cm across). closed the door and by that time i already heard drafting. Wood input was 7.5kg of beech hardwood, one season dry.
17:10 Up untill this time it was lighitly smoking and sometimes not smoking at all. I heard the roar but not that powerfull. In tese 20 minutes my glass was dripping wet so i guess that the problem was in my stove being put up outside in the humid air with temperature of -5°C to 5°C and never more. So the humidity had to be removed prior to entering into fully functionaly rocket stove.
17:15 Just before this time it started to smoke VERY profoundly like just before some larger pieces of wood catch fire. And then the smoke was gone up until the end of burning. At this time the glass door was really dripping wet! And after a few minutes the drops were dried and gone for good.
17:20 flashover started under the metal box (seen in previous posts)
17:25 Lower half of firebox whitened by the fire (upper half and aluminium p-channel still blackened). The metal box is glowing. Barely it is also visible at the sides. It was late dawn and metal box was galvanised.
17:55 End of flashover
18:10 End of flames in batchbox. Lots of coals (2 litres).
19:50 About 1/3 of coals still present (compared to before).
21:10 A handful of glowing coals still present.
That's about it.
It took 25 minutes to get to "smokeless" rocket mode". Is this what is to be expected if you have cold and humid firebox?
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Post by peterberg on Feb 2, 2013 4:54:32 GMT -8
Yesterday i did another test with it. SPECS: 6" system batchbox horizontal feed with p-channel and closed front doors (with primary air intake at the bottom of the doors opened to about 40-50 sq.cm... Air intake could be smaller, my own setting is 25 cm2 (4 sq.in.), but that stove is coupled to an adequate chimney stack. It took 25 minutes to get to "smokeless" rocket mode". Is this what is to be expected if you have cold and humid firebox? Hmmm... this is odd, your first testrun, stove still wet and all, went better. The differences as I see them: there's some kind of hood over the riser, mimicking a barrel. How large is that gap between end riser and steel sheet? It's best not to use the recommended gap as mentioned in the book, this thing tend to run better with more "headroom". Mine is running impeccably with a "top gap" of 100 cm (3.28 ft). This doesn't mean you have to do the same, the top gap could be very much larger, that's all. Second: My prototype will run sluggish using wood containing more than 15% moist. The dryer, the better it'll run. So, your fuel could be too wet, perhaps it would be wise to buy a moisture meter? In general, smoke should disappear within 3 minutes, 10 at the most. Stove cold or not, that doesn't matter. When the fuel isn't totally dry, split it in thinner pieces. In this way the fuel surface is enlarged and the water will be driven out faster. And let's be honest, one season drying time for a hardwood like beech is far too short, 3 years would be adequate when kept out of the rain. |
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dvawolk
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DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Feb 2, 2013 9:17:37 GMT -8
The differences as I see them: there's some kind of hood over the riser, mimicking a barrel. How large is that gap between end riser and steel sheet? It's best not to use the recommended gap as mentioned in the book, this thing tend to run better with more "headroom". Mine is running impeccably with a "top gap" of 100 cm (3.28 ft). This doesn't mean you have to do the same, the top gap could be very much larger, that's all. My gap is about 10 to 11 cm (4 in). Today is snowy/rainy weather. When it stops raining, i'll do a testrun without that metal box over it or i'll try rising it. Also in the following week i'll get barrels to test with them. Does that mean that batchboxes aren't suitable to use in a similar way to original rocket stove (with barrel over heat riser?)? Is 100cm or more of a gap required? That would mean that it should be used only if a "first bell" has inner height at least 100cm over the heat riser? That feels like a large distance to me. My prototype will run sluggish using wood containing more than 15% moist. The dryer, the better it'll run. So, your fuel could be too wet, perhaps it would be wise to buy a moisture meter?... ...And let's be honest, one season drying time for a hardwood like beech is far too short, 3 years would be adequate when kept out of the rain. I would say that my wood moisture is above 15%. I totally agree that one year is too short for a wood to be dry especially if it is not split at the beginning of drying. I will test it tomorrow with neighbor's tester. And I'll put 10 kg of wood somewhere warm/hot inside the house to dry it for a week or so and then test again. I would ask again here regarding the gap of primary air intake (and secondary also. Yours works with 15% primary and 5% p-channel air intake (percents of system C.S.A.). But setting is only useful for your particular draft strength. If i don't have a chimney (or if it will be higher) then i should set these differently. That would mean if i have a lesser draft, then the openings should be wider, probably both of them. And then it comes to a slight problem when trying to widen the p-channel? And again it is hard to regulate the air intake openings without test meters - or are there any visible parameters that is good to be aware of? Klemen |
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Post by satamax on Feb 2, 2013 10:37:39 GMT -8
Well, i gonna get a slap on the head, but imho there's a gap which rocket stoves seen not to like. About 1.5 to 2 inch, seems fine, as in a proper rocket. Then you get in the four inch territory, it seems that there's turbulence created and it draws less, then you get over 6 inch and you enter bell territory, and it works better, tho, diferently. The cooling doesn't work the same with the convection movements into the bell. Mind you, this is based on about four prototypes and friends experiments/feelings. And not in any ways reliable. ;D
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Post by peterberg on Feb 2, 2013 13:37:13 GMT -8
That would mean that it should be used only if a "first bell" has inner height at least 100cm over the heat riser? That feels like a large distance to me. For me too, and I didn't say anywhere that would be the minimum headroom. The following is what I wrote and that's quite clear I'd think. "This doesn't mean you have to do the same, the top gap could be very much larger, that's all."This 10 cm you mention should be adequate for this stove, more wouldn't harm. I would say that my wood moisture is above 15%. I totally agree that one year is too short for a wood to be dry especially if it is not split at the beginning of drying. I will test it tomorrow with neighbor's tester. And I'll put 10 kg of wood somewhere warm/hot inside the house to dry it for a week or so and then test again. A week drying time is far too short, unless you'll dry the wood in an oven. Try it, after a week, it's best to split it again and test the fresh split side with the moisture meter. That would mean if i have a lesser draft, then the openings should be wider, probably both of them. And then it comes to a slight problem when trying to widen the p-channel? And again it is hard to regulate the air intake openings without test meters - or are there any visible parameters that is good to be aware of? Calm down, I've done dozens of tests, shortcutting the chimney, reducing initial draft to as little as 0,01 millibar. My stove didn't show any sign of a slow start up with this draft value, the air inlets at the values I mentioned before. Widening the air openings with a lesser draft won't help at all, by the way. These stoves, the J-tube shape as well are very much depending on air velocity. That won't be higher by adding a larger volume of air at a given draft, rather the contrary. Again, use really dry wood and I do expect the stove will work as intended. |
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Post by peterberg on Feb 2, 2013 13:46:49 GMT -8
Well, i gonna get a slap on the head, but imho there's a gap which rocket stoves seen not to like. About 1.5 to 2 inch, seems fine, as in a proper rocket. Then you get in the four inch territory, it seems that there's turbulence created and it draws less, then you get over 6 inch and you enter bell territory, and it works better, tho, diferently. The cooling doesn't work the same with the convection movements into the bell. Mind you, this is based on about four prototypes and friends experiments/feelings. And not in any ways reliable. ;D Max, During 2011 I've tested literally dozens of configurations of the J-tube stove, albeit on a small scale. These small stoves are notorious to get right, and yes, there's a difference. Using a small gap, usually the rocket sound is more pronounced. However, the performance of the stove, in terms of clean burning weren't any better or worse. My test equipment and my feeling didn't agree with each other a couple of times. |
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Post by endrunner on Feb 2, 2013 21:59:16 GMT -8
We are the company that has licensed Peter's j-tube design. We hope to be able to ship the cast refractories within a month or so if you are interested.
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cab
New Member
Posts: 33
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Post by cab on Feb 3, 2013 10:04:18 GMT -8
We are the company that has licensed Peter's j-tube design. We hope to be able to ship the cast refractories within a month or so if you are interested. How about some photos and size info? |
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Post by mechartnik on Feb 3, 2013 12:26:36 GMT -8
cab, search her previous posts to find it, it's sweet
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Feb 3, 2013 13:00:59 GMT -8
We are the company that has licensed Peter's j-tube design. We hope to be able to ship the cast refractories within a month or so if you are interested. link to your previous post added! Where are you located? Where will you be able to send these? Klemen |
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cab
New Member
Posts: 33
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Post by cab on Feb 4, 2013 6:27:10 GMT -8
Thanks....
Best of luck with the venture.
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dvawolk
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DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Feb 20, 2013 14:27:55 GMT -8
So. In the last few weeks. I got drums (From motor oil, 200L) and i put one over the heat riser. The gap between heat riser and top of the barrel was 30cm (12"). The exit was on the bottom of the barrel, 16cm (6 1/4") diameter -the stove is maid for this diameter. Starting the fire soon the temperature by the exit of the barrel went over 200°C (390F) and i had to pull out the probe (had poor probe, now i have better one). Here the problem started when the remainder of oil in the drum began to smolder. That was really messy - if i knew that was coming i would definately clean them before... The problems went on: i had aluminium p-channel insert that totally melted to the top of batchbox. So the temperature was definately above 660 °C. After that i rebuilt the whole thing with smaller bricks i get to got. The new dimensions of a new batch box are: height: 33cm width:22cm length:44cm PORT: 22cm x 5.6cm ( calculated to 70% system CSA it shoudl be 6.4cm wide - i started building too fast and did a wrong calculation thatswhy it's too narrow) P-channel is 20x60mm with 2mm thick wall. It is INOX now  Next, i started (already dried) burner and the draft was here right away. First five minutes a minimum smoke and after that lots of smoke. I am quite certain that it is not from oil as the drum is dry looking, certainly not oily but with soot all arround. The smoking continued to the end of flames. After the first 15 minutes the flashover appeared and still i could smell and see unburned gasses. The flashover reached drum ceiling but soot stayed in place - i expected the soot burn at that time but nothing happened - i assume that there was not enough oxygen. RIGHT? Do you think that all this started because of to small port opening?Tomorow i take off the drum and light the thing. Compared to previous model it SHOULD burn smokeless in less than 15 minutes, unless the problem lies in the port witdh. ALSO i was drying a piece of wood in my electrical oven (after baking) and found out that humidity in wood is AT LEAST 20%. Probably i can not expect fast coming smokeless stage but if i got to smokeless in 15minutes before, i SHOULD get there in same time AGAIN. Technical clarification: If i have an option of using a port that is 6cm long or 3cm long- a better option is 3cm? Peter, you say keep it short. But When you did refractory i think it was about 5cm? So, what is optimum? Is it even better for the port to be wider on the batchbox side and then have the exact CSA on the heat riser side? Like that: ----------- BATCHBOX IIII\.../IIII IIIII\./IIIII HEAT RISER ----------- Some measures: Outside temperature is 0°C. Today i measured temperatures and it was abit windy... when flashing over, temperature 10cm (4") below the top of barrel reaches 430 °C. When starting the stove the exhaust temperature from the barrel goes up about 50°C per 5 minute. That's it for now. Please, comments, suggestions... |
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Post by peterberg on Feb 21, 2013 3:23:11 GMT -8
The exit was on the bottom of the barrel, 16cm (6 1/4") diameter -the stove is maid for this diameter. You don't mention the rest of the thing. Is there a bench, bell, chimney or whatever downstream? I could have told you about the oil burning in the drum, it's very messy, been there, done that. The p-channel will get quite hot there, yes. You have to use mild steel as a minimum, inox is indeed the better choice. Next, i started (already dried) burner and the draft was here right away. First five minutes a minimum smoke and after that lots of smoke. I am quite certain that it is not from oil as the drum is dry looking, certainly not oily but with soot all arround. I would suspect the oil in the barrel as the ongoing source of smoke, even when it's looking dry inside there's a film of scorched mineral oil in there. My Testo analyser couldn't measure that but the oil ended up as goo inside the analyser and suffocated the oxygen cell. This smoking isn't due to a shortage of oxygen, otherwise there couldn't be such a high temperature at the top of the barrel. The only other cause I can think of is an exhaust opening in the drum which is too narrow. Please read the Helpful hint thread carefully. That moisture percentage of 20 is far too much. The dryer the fuel, the shorter the smoke period. My experimental model has had a port depth of anything between 110 mm and 40 mm. The latter was definitely the better of the two, no difference between 40 and 50 mm though. Building the port as a funnel shape could be done, whether or not this would generate better results, I don't know. |
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Feb 21, 2013 6:30:41 GMT -8
Peter. At this previous setup i only had one drum over the heat riser with the mentioned gap. There was no exit flue, only exit hole (in the bottom of the drum and not in the side walls) with diameter of 16cm. Since everything was smoking and smelling badly i didn't went on with the description - i am quite certain that the problem was with smoldering oil (before the drum over the heat riser i was using that metal galvanized box and it did't smoke after 15minutes or so (thanks for those 15 minutes probably goes to 20% or more humidity in the wood)...
I decided for a rebuild because i used AAC for heat riser and for the ceiling of the batchbox. It became very brittle and the ceiling cracked,too. So i rebuilt it.
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Feb 21, 2013 7:23:34 GMT -8
Now, to the rebuilt version:
Dimensions of new batchbox are slightly smaller but similar have been already tested. All is chamotte brick except upper 80 cm of heat riser which is insulative and high temperature resistant.
And, ah, DARN, now it struck me! Ahhh. I am confusing 16cm with 6". Dimensions of the tunnel are all right for the 15cm (or 6" model). I just need to change the heat riser CSA from 16cm x 16cm to 15cm x 15cm. And then all the measures will be okay.
ANYWAY---
I just burned one batch and without drum it works smokeless (after 15 minutes or so).
I also put on the 200L drum (i cut out the whole bottom). This adds to about 1.75 sq. metres of steel (if material would be brick than it would should measure 3.5 sq.meters for a similar heat extraction.). The gap between the top of the barrel and heat riser was about 25 cm (10"). The thing stayed smokeless.
I didn't take any measures today i just wanted to know will it stay smokeless or not...
Also i cleaned two drums and i will connect them to get about 3.25 sq. meters of surface (that would be roughly 6.5 sq. meters for brick material. And this is approximately what i am after in the end...
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