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Post by Rinchen on Mar 12, 2012 4:20:43 GMT -8
I have started working on some idea's how to convert the feed tube of a standard J-tube system into a firebox. I have had much inspiration from Peter's experiments and I have had a look at some wood gasifier designs since they have a fuel box that I think could work well with a rocket. So if it works for gasifiers...
I have gone through a few iterations with a firebox on top of an existing feed tube with a firebox and nozzle in it.
Here is some configurations I tried working out:
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Post by Rinchen on Mar 12, 2012 4:26:31 GMT -8
and
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Post by Rinchen on Mar 12, 2012 4:30:09 GMT -8
And this...
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Post by Rinchen on Mar 12, 2012 4:43:53 GMT -8
Neither of these seem to deliver a satisfactory configuration. Either its too close to the heat riser, difficult ash cleanout, large height, to name a few shortcomings...
So I think this is a more workable design and sticks closer to the initial J-tube with air coming in from the top through the wood. Air inlet I think should be either at the front or the sides, about as high as the original feed tube, starting point 20% of system size. At the entrance of the burn tunnel can be a delivery of secondary air for instance by means of the "Peter Channel". Which is a slot through which air enters from the top 5% of system size.
Loading door can be either from the front or the top, made from stone, concrete, steel or even a glass door with steel frame. The glass in my opinion would be a waste of time and money unless you already have one lying around, because you will be mostly looking at wood that is not burning, since the burning is happening at the bottom and back :-)
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Post by Dan (Upstate NY, USA) on Mar 17, 2012 6:00:41 GMT -8
That is how I wanted to build mine, but I didn't have enough room in my living room, so I had to build my firebox sideways to the burn tunnel.
I am heating with the stove but I am using it the traditional way (feed tube going down) until I can finish the rest of the stove.
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Post by Dan (Upstate NY, USA) on Mar 17, 2012 6:02:16 GMT -8
I don't believe you could have gotten your first two designs to work, I think your third will work.
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Post by Rinchen on Mar 18, 2012 5:48:20 GMT -8
I haven't tried the designs yet, but you are probably right. Standard J-rockets can be difficult enough to start already, you will need a surplus of chimney draft to start it up. Not too sure yet about any of the designs though. I think there are still some things to consider to make it work properly.
When I was looking at your pictures before I thought 'ah he is making a bigger feedtube, interesting' and then later it showed a standard size feedtube, so I was a bit puzzled why there is such a big box around it :-)
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Post by bmeagle on Apr 2, 2012 6:35:30 GMT -8
I like what you guys are coming up with here.
I've been wondering how to increase the wood capacity to make longer burn sessions possible.
I'll have to consider some more designs it seems!
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Post by Rinchen on Apr 3, 2012 0:39:19 GMT -8
I have been giving this quite some thoughts and have also looked at other systems and designs. I have reached the following conclusions: - Downdraft wood burners/gasifiers are one of the most efficient wood heaters
- Downdraft needs to have a strong draft in order to keep the process going well
It turns out that the standard J-tube is a very well balanced naturally aspirated downdraft wood burner. In order to be able to increase the cross sectional area of the feedtube, your draft will need to increase equally. This can only be done by lengthening the riser, but this will give you other things to think about, like increased drag, larger temperature drop (no insulation is perfect) and longer heatup times. Not to forget an even taller contraption. For this reason I think it is why no satisfactory solutions have been found yet. You best bet is to have longer fuel that you can load into the feedtube. Be aware though of the dangers of your fuel catching fire or tumbling out the feedtube. One important design factor that is not in the book, but that I have come to understand because of Peterberg's work is that the bottom of the feedtube (about the height of the burn tunnel) needs to be well insulated and as hot as possible, yet above that the feedtube needs to be cooled! This will reduce firecreep, but also stabilize CO production when the system is well heated up. So best to build the upper part from steel somehow and even better to actively cool this with secondary air. You will find more information on that in the thread donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=355So for me personally the quest to improve J-rockets has ended. J-rockets are exactly what they say they are, efficient wood burners that are easy to build for people who like to tinker with fire. |
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Post by Rinchen on Nov 16, 2012 2:49:23 GMT -8
Well guys,
I have kept it quiet for some time, because I wanted to collect some user experience before posting, but the developments of Peter gave me the courage to rebuild the feedtube like I proposed in the RocketDesign3 image above in this thread. It is not quite the same as the horizontal batch box that Donkey, Canyon and Peter have been working on, but it allowed me to do a rebuild with minimal changes to the existing system.
After having used it daily since the beginning of October I can say I am very pleased with the result.
I no longer need to chop any wood or stay with the stove to feed it. The power output has about doubled and I think the burn has become a little less efficient, because I can see a light soot buildup on the thermometer pin that sticks in the chimney base. Nevertheless its still pretty clean compared to the neightbours with a fireplace insert... My wife once smelled something outside that reminded her of smoked salmon when the stove was roaring :-)
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Post by Rinchen on Nov 16, 2012 2:52:22 GMT -8
And a full view of the thing. The floor has been replaced and is now a stone look laminate.
PS there is another 3 meters (+- 9 foot) of bench on the other side of the left wall which is the kitchen.
Exaust temperature at peak is between 100C (212F) and 110C (230F).
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Post by Rinchen on Nov 16, 2012 2:55:53 GMT -8
Since Donkey has recently replace a burned out barrel for the sauna Rocket I dont expect this barrel to live 10 years either because with a full load the top gets cherry red with a diameter of about a foot.
PS pizza's are done in no time :-)
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Post by Rinchen on Nov 16, 2012 2:59:55 GMT -8
PS for who would like to see, here is the Sketchup of how I build it
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Post by matthewwalker on Nov 16, 2012 10:03:23 GMT -8
That looks great rinchen! Care to detail your door construction? It looks like maybe you cast an insulated part and lined it with steel? Great looking stove, I bet with all that mass it's doing a great job of warming the space.
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Post by Dan (Upstate NY, USA) on Nov 17, 2012 16:44:30 GMT -8
I would love to see how you load this stove, a video fo it burning etc.
This gives me hope that my firebox will work too when I get around to building it.
Thanks for the post...!
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