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Post by Rinchen on Oct 26, 2012 3:39:36 GMT -8
Peter, we haven't heard about you in à while, whatcha'r upto? Some rockety stovety missbehavin? ;D Hi Max, Nothing new or special. Most of my time (of which I do own a lot, time is money so I am filthy rich) is going into wood hauling and processing. My fuel stock has been severely depleted by this silly rocket stove experiments and my Testo analyzer broke down again, big time. Repairs will be very costly but there's no alternative. More experimentation has to wait until spring I'm afraid. Hi Peter, Perhaps the "condar dilution tunnel" that is used by Lopez Labs could be an alternative testing method until your Testo analyzer has been fixed. Of course you cannot compare it with Testo data so you will need to establish a new baseline. |
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Post by satamax on Oct 28, 2012 3:55:35 GMT -8
Ready to get out and be tried, if only i can find somebody willing to help!  |
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Post by satamax on Oct 28, 2012 11:01:13 GMT -8
Well, gave it a try, and it's smoking like mad. More insulation is in order i think.
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Post by peterberg on Oct 28, 2012 13:05:06 GMT -8
Well, gave it a try, and it's smoking like mad. More insulation is in order i think. Let me guess. You wheeled the thing outside, placed the top half of the bell and lit the fire. How close is the top of the bell to the top of the riser? Where's the exhaust opening situated in the bell? Have you tried to run the thing with or without an improvised chimney stack? Without the top half of the bell, was it still smoking like mad? |
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Post by satamax on Oct 28, 2012 14:14:08 GMT -8
Hi Peter.
Well, there's about 38cm between the top of the heat riser to the very top of the bell. The outside of the heat riser is about 15cm from the back. I have cast the bottom of the heat riser, about 30 or 40cm with castable refractory/vermiculite mixture, the top is pure vermiculite. I have reinforced the back walls of the batch box with that mixture too. Well, it was about -3C° outside, with a fair bit of wind. This needs to be re tried. The bell top being rather hard to fit or remove, it stayed on. I'll buy four handles that i will fit on it, tomorow i hope. I hope the wind stops too. I haven't put any chimney on it. Just a hole at the batch box level. 150mm diameter. Thickness of the bell is about 4 or 5mm steel.
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Post by peterberg on Oct 29, 2012 1:21:19 GMT -8
I haven't put any chimney on it. Just a hole at the batch box level. 150mm diameter. Max, Thanks for the explanation. As far as I can see, everything is alright, insulation OK, room around the riser OK, top of the bell is beautifully shaped to guide the stream OK, since the refractory/vermiculite is cast around the firebox there should be no leakage OK. And you have to use the sloped sides of the firebox, but I'm inclined to think you did. That leaves us the water in the refrac./vermiculite which could be a substantial amount. This has to evaporate before the firebox will come up to temps. That shouldn't prevent clean burning as a whole, the thing has to go through a running in period so to speak. But... there's no chimney stack to drive the gas velocity initially. This is not OK, add a steel elbow and at least 1 m (3.3 ft) of ordinary stove pipe. This has to reach at least above the bell and even then, you have to start with a very small fire. Just a handful of splinters right in front of the port, a lighting fluid or one of those barbecue lighter block things and blowing gently usually will do the trick. And patience is necessary too. ;D |
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Post by satamax on Oct 29, 2012 7:06:58 GMT -8
Hi Peter, well, i retried with the bell off.
It's smoking back a bit at the mouth or the burn tunel. With the V, i have only about 10cm of opening above the wood. I wonder if it isn't a bit small. And that's the case where i'm not loaded much. Do you think i can open à bit more towards the top? Up to the ceiling?
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Post by peterberg on Oct 29, 2012 8:54:18 GMT -8
It's smoking back a bit at the mouth or the burn tunel. With the V, i have only about 10cm of opening above the wood. I wonder if it isn't a bit small. And that's the case where i'm not loaded much. Do you think i can open à bit more towards the top? Up to the ceiling? The space above the wood is alright, opening up the port is a bit premature at this stage. Before you are going to modify things, it would be better to get rid of the water in the refrac, don't you think? I have seen it happen, when the stove was ran outside with the firebox and riser only. It proved to be a bit tricky, which solved itself completely when brought inside and being coupled to a chimney. In fact, at the moment I am using my prototype to heat up the workshop, running the stove completely open. |
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Post by satamax on Oct 29, 2012 8:57:35 GMT -8
Peter, i think it's dry by now, i's been sitting since last thursday in the workshop. I've noticed that the outside of the heat rised, where i have cast it with refractory and vermiculite, gets hoter than i'd like. Compared to the top where it's pure vermiculite.
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Post by peterberg on Oct 29, 2012 11:32:16 GMT -8
Peter, i think it's dry by now, i's been sitting since last thursday in the workshop. I've noticed that the outside of the heat rised, where i have cast it with refractory and vermiculite, gets hoter than i'd like. Compared to the top where it's pure vermiculite. You really need to run the stove a couple of times in order to get the water out. The vermiculite is hygroscopic, the water won't get out just by storing the stove dry. The moist will transport the heat to the outside a lot easier than the vermiculite/refrac by itself. And of course the vermiculite used on its own will insulate better, it contains less mass. |
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Post by satamax on Oct 29, 2012 11:37:39 GMT -8
Well, did another try.  With tubes, runs a smidge better. Tho, i still have smokeback. you see the blackened edge of the firebox? May i ask, why do you say no more than 70% CSA for the opening? Rocket stoves, ok, they don't have a batch box, but they have full opening  |
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Post by peterberg on Oct 29, 2012 12:28:26 GMT -8
May i ask, why do you say no more than 70% CSA for the opening? Rocket stoves, ok, they don't have a batch box, but they have full opening Let's say this isn't a normal rocket stove. It's not a normal stove at all for that matter, as such it's only half a year old in this form. The 70% came out of a series of very thoroughly testing, delivering the best results without too much of a hassle. The narrowing of the port and expansion behind it do provide a rigourous turbulence, that's why it is running so clean. The gas speed in the port is very much higher compared to the firebox. When this velocity isn't high enough, the gas speed in the firebox could be too low, resulting in smoking back. Gas velocity is coupled to temperature obviously, too much moist will keep the temperature down. It's important to allow the device a running in period of 10 to 20 runs, preferably coupled to a chimney. When it's still stubbornly smoking back after that, it's time to alter the configuration. The stove you are building is the first of its kind, after all. In short, making the port larger will inevitably result in less clean combustion. When you are alright with that, go ahead, it's your gizmo. Edit: Oh yes, Ianto Evans rocket stoves have full opening, and suffer smoke back now and then as well. |
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Post by satamax on Oct 29, 2012 13:09:37 GMT -8
Well well well.
It's kind of a gut feeling that the heat riser isn't guzzling enough for some reason. Air velocity in the box isn't fast enough.
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Post by peterberg on Oct 31, 2012 12:21:31 GMT -8
@max,
All parts of the stove passed the scrutiny in earlier posts. But today it dawned on me: one detail has been escaping our attention. That's the infamous area known as the manifold in normal rocket mass heaters. The exhaust is low at the right side of the firebox. Would you please tell me the shape of the space around it and its dimensions? Something do tell me a possible bottleneck could be in that area.
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Post by satamax on Oct 31, 2012 13:02:35 GMT -8
Hi Peter. Thanks a lot for the reply. Well, in this pic, you can vaguely see. I have about 8cm between side insulation, and the 150mm hole. Heat riser is 160mm. Pipe is 153mm diameter. I have about 376 cm² of area between the insulation and the circumference of that hole. 201cm² csa for the heat riser. 176 for the exhaust. IIRC about 147cm² for the box port. Can't calculate the segmentright now, but i think i'm ok. sphotos-c.ak.fbcdn.net/hphotos-ak-snc6/253078_2548799496713_1444896415_n.jpg |
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