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Post by patamos on May 5, 2015 8:17:42 GMT -8
Thanks Shilo and Matt for the correction on extra primary air having a cooling effect. I was thinking maybe it was somehow creating a stronger throttle effect.
I've had some interesting chats over the past 2 years with a rep from Clayburn Refractories, the nearby makers of firebrick here on the west coast. His take is that the high temperature rating does not equate with added tolerance to repeat thermal cycling at less than peak temperatures. That said, when i salvage Clayburn fire bricks from older fireplaces, i notice that their High Heat Duty bricks are in much better shape then their Mid Heat Duty bricks, and way better shape than the softer firebricks that are commonly available.
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Post by Robert on May 7, 2015 2:21:02 GMT -8
Its all depend on an Aluminium Oxide (Al203) content in the brick... for good thermal shock tolerance it should have around 25-32%....
The industrail brick that can take more heat, but less thermall shock have 62 and more percent...
Sometimes it is easy to see which brick is which... it is written Al32 or Al62... than you know... otherwise you ask a suplier or a producer about the percentage of Aluminium Oxide.... sam goes with the refractory cement...
cheers
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Post by pyrophile on May 9, 2015 13:42:50 GMT -8
Matthew, I find that you found out a nice way to build a low and compact burner for a wood cookstove!
I have a question about the tube for secondary air : I suppose that you expose its slot towards the narrow burning channel (where you put a window of ceramic glass), that is the slot turned to the left side. But the space is rather narrow there!
Maybe, I did not understand well (my english...). Would you have photos showing how the secondary tube is inserted?
How many centimeters at this point where the firebox joins the going to the feft narrow burning channel?
I also have another question (if I don't ask to much...) : on the second level of your shown construction (above the base), one can see two square parts made of bricks, the larger where flames finish their way and, just before, a smaller one.
You didn't cover this little passage (the little square) going to the square hole where flames finish their way. You let there this kind of little square bell (I see bells everywhere). Is there a reason not to put a brick at this stage- to prevent the existence of this little square bell where gases will rise a bit?
Benoit
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Post by matthewwalker on May 9, 2015 19:04:56 GMT -8
Hi Benoit,
I don't have a good photo of the secondary tube location within the firebox. The port is roughly 2 1/16" at it's narrowest, and the tube is about 1.5" from each wall.
The little squares I think help combustion, although I'm not 100% sure.
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Post by peterberg on May 10, 2015 11:51:59 GMT -8
What that little bell possibly could do is inducing turbulence along the top of the tunnel. The gases are passing underneath and by doing so, the pressure in that void is getting lower. A very little bit, but nevertheless. So yes, there's a possibility that it is contributing to more complete combustion this way.
In order to check this is true, it would be necessary to rebuild the thing slightly, without that little top bell. Then test it again and see whether it makes any difference. When the answer would be yes, then test how much and in what way, positive or negative. Looks like a job for a pensioner with a lot of time on his hands plus a Testo analizer.
Any takers?
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adiel
Junior Member
Posts: 119
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Post by adiel on May 10, 2015 12:30:07 GMT -8
wow. peter. are you in on this?
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Post by peterberg on May 10, 2015 12:49:39 GMT -8
Not a chance: my own rocket/bell (new design) is on its way, slowly. Hope to have that ready in September(ish). After that there's another US trip on the horizon plus scavaging for winter fuel supply. Thank heavens this doesn't need to be a lot. During winter, there's a choice of things to do but I like to take it easy these days...
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Post by pyrophile on May 11, 2015 11:35:37 GMT -8
This little bell is a kind of inverse trip wire : a void instead of a relief!
Matthew, the slot is of course oriented towards the port, that is to the left, isn't it?
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Post by peterberg on May 11, 2015 13:17:51 GMT -8
This little bell is a kind of inverse trip wire : a void instead of a relief! Yes, that's right, a good description. Seems to be found out by again another guy who's never been on the internet. Lasse Holmes (canyon) told me about him, probably someone in Alaska fiddling with rocket stoves but I'm not sure about that. I figured out why it could be beneficial but it's an educated guess (again). |
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Post by matthewwalker on May 11, 2015 20:05:58 GMT -8
Yes Benoit, the slot is oriented to the left to be centered in the port.
So, yes, when we were spending time together in Eugene this winter, Lasse told me about this fellow in Alaska who had a (I think) metal rocket J with a vertical tube, closed, rising from the top of the burn tunnel. He speculated that the void could act as a capacitor, or maybe we did? I wish he would tell the story....anyway, that the void could capture hot wood gas and meter it into the combustion zone at a rate the stove could handle, or something like that.
My brick stacking experiments when I returned home created that shape naturally, although I do intentionally try to have the top of the port lower than the ceiling of the chamber, following Peter's example. I think there's something to that, so, yeah. I think of the brick that forms the top of the port as a spill way, upside down. But the negative space created makes the little void, other wise known as The Capacitor.
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adiel
Junior Member
Posts: 119
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Post by adiel on May 12, 2015 21:28:15 GMT -8
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Post by independentenergy on May 13, 2015 2:16:25 GMT -8
Adiel , I got the same results . . .
So much smoke to leave, added a few extensions to Riser slightly better . Smoking also back from the door.
Test run without chimney .
It does not seem the operation of a rocket stov.
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Post by johndepew on May 13, 2015 9:59:03 GMT -8
I had trouble getting it to work as just a core as well, but Matt has said it pretty much has to be installed inside a sealed stove to work. In that way, it's different than a typical rocket or batch box core.
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Post by independentenergy on May 13, 2015 13:59:48 GMT -8
So you have to venture a building without the usual testing of the core . . . If so , the type of bell after the core affects performance
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Post by shilo on May 13, 2015 17:41:48 GMT -8
So you have to venture a building without the usual testing of the core . . . If so , the type of bell after the core affects performance You need a bypass |
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