|
|
Post by velacreations on Dec 30, 2008 9:20:36 GMT -8
What do folks think about this design: e-avanstove.blogspot.com/Basically, it has a secondary air input in the heat riser to help burn the wood gases more efficiently. Has anyone experimented with such a design? I think a pipe that entered the burn tunnel and up into the air riser would achieve the same result. Anyway, what do you think? |
|
|
|
Post by Donkey on Dec 30, 2008 11:10:18 GMT -8
I've often wondered if a secondary air channel into the heat riser could help.
The basic J tube design appears (without peterbergs fancy equipment to know for sure) to burn quite cleanly as it is.. Which is sort of odd on it's own right, few stoves do well on primary air alone.
It's pretty important to get just the right amount of air in there.. Too little and the fuel (smoke, etc) can't burn. Too much will cool off the stove, reducing burn efficiency..
I'd just have to say that someone needs to do the experiment. It's certainly worth the try.
|
|
|
|
Post by canyon on Dec 30, 2008 12:24:52 GMT -8
Thanks for the link. These are some things that have been on my pondering/tinkering mind as well. I like the removable grate/ ash pan idea. I wonder why the 45 degree feed? I guess it is a compromise to make it easier than horizontal and still employ the easy ash collection? Seems it might not work as well as vertical both in gravity feeding and having less turbulence? When are we going to have the international rocket convention with peterberg bringing the test equipment?  |
|
|
|
Post by velacreations on Dec 30, 2008 14:50:42 GMT -8
I think the 45 degree feed is so that they can add all sorts of biomass fuels in there. Smaller fuels will naturally fall down into the fire.
As for the secondary input idea, I think it is definitely worth trying. There are lots of wood gas furnaces that can melt metals very easily, so I think getting it up to temp would not be a problem, but you definitely don't want to cool off the zone. I think if you added air above the zone, you could burn the gasses easily with the added oxygen and the result would be a much more dependable system. I don't know for sure, though!
|
|
|
|
Post by larsmith on Dec 31, 2008 6:14:32 GMT -8
re: secondary combustion, I've found that my heater runs hottest & best when I've placed 4-6" "chunks" of wood in the burn tunnel as well as the feed "tube". I develop a super ash bed in the "pot" at the bottom of the feed tube and then stand 1 or 2 six inch chunks of wood on top of the ash bed. ( remember, my system's air flow passes thru an opening which is 4.5 by 9 ) If I keep the ash bed healthy, the gasses from that get burned a second time as they pass thru the flames which rise from the "chunks" which I place in the burn tunnel. The combustion in the burn tunnel creates a great draft which in turn sucks the oxygen-rich air down on top of the ash bed & the pieces of wood standing in it. The two thrive off of each other !! It's the most incredible thing to watch. I figure that to one extent or another, the gasses from the wood which stand in the ash bed are being "secondarily combusted". For the record, I've found that my heater design is very easy to start up, tho I use a propane torch to light up the news paper and the kindling wood. That's a small expense to go to in order to get this unit functioning as quickly and as efficiently as possible. To read the thread and find a link to the video I posted re: my heater, check out : donkey32.proboards104.com/index.cgi?board=discuss&action=display&thread=84 |
|
|
|
Post by Donkey on Dec 31, 2008 9:40:56 GMT -8
peterberg is the only one I know of that has brought in secondary air for his stoves. 'Course, his stoves are a bit different all 'round. VERY cool, and they work really well, just a different layout. You can follow his journey at the Rocket Bell Stove thread |
|
johnf
New Member
Posts: 18
|
Post by johnf on May 4, 2009 18:19:40 GMT -8
It would be really interesting to see this with attention paid to pre-heating the secondary air. Not so easy to do with the simple brick stack stove body, but how about with cast mix/matrix?
For a big household cob rocket, a pottery pipe laid up along the vertical burn tube, to a sort of "plenum" built of bricks stacked around the tube, with enough gap to admit the air that's been drawn up the tube.
If the stove's guts could be made from simple cast materials, how much ducting could be cast into it in this way?
Much experimentation is needed in casting vermiculite/clay pieces.
Following several ideas I've seen on the interwebs with secondary air in DIY projects, I'm about ready to start cutting & bending metal on some concepts. I like the 45degree fuel feed for some utility in self-feeding, though I've found in small projects that bottom burning fuel sitting in the feed chute catches fire easily along its entire length, if there's any chance.
|
|
|
|
Post by Donkey on May 4, 2009 19:46:14 GMT -8
It would be really interesting to see this with attention paid to pre-heating the secondary air. Not so easy to do with the simple brick stack stove body, but how about with cast mix/matrix? For a big household cob rocket, a pottery pipe laid up along the vertical burn tube, to a sort of "plenum" built of bricks stacked around the tube, with enough gap to admit the air that's been drawn up the tube. If the stove's guts could be made from simple cast materials, how much ducting could be cast into it in this way? Much experimentation is needed in casting vermiculite/clay pieces. I've been putting a bit of thought into the casting question.. Seems to me that with some forethought, there should be VERY LITTLE that can't be cast. I can imagine places where a pre-made metal (or clay/ceramic) part would be laid into the casting, funny corners with secondary air piping, waste oil burning attachments, turbulators and flame holders come to mind. If parts are cast in discreet layers, modularity can be introduced with interchangeable parts and options.. Seems to me that having a stick burning along it's length is something to AVOID.. Really, you want it to burn ONLY at the optimum place for maximum efficiency. Often, in horizontal feed systems it's an indication that your under air opening is too large and the plate needs lowering. In vertical feed systems, the mouth of the feed may be too large a volume and needs tightening. Sometimes it's just that the wood is light and catches fire all too easily.. Not much to do about that but burn heavier, harder woods.. I think that you are on a really interesting track and am looking forward to hearing more once you've bent that metal.. |
|
johnf
New Member
Posts: 18
|
Post by johnf on Feb 14, 2010 23:55:59 GMT -8
Seems to me that having a stick burning along it's length is something to AVOID.. Really, you want it to burn ONLY at the optimum place for maximum efficiency. Clarification: yes, that's how I meant it. I've been tinkering with small things (under 2" diameter tubes", and the entire coffee-can body get hot enough that any wood touching it will smoulder/burn. Manual feed of small chunks is the only way. I had been able to avoid it somewhat by having the air inlet only along the fuel itself, so any burning is being sucked in. You're correct in that anything else is a seperate flow, and that's not what we want -one way in, and out up the burn tube. As I toy with secondary air, I'll need to make sure this follows too. |
|
