|
Post by peterberg on Mar 8, 2019 5:00:46 GMT -8
Now I come to think about it... Maybe, just maybe, there's a way around the necessity to have a downdraft gasifier run in updraft mode in order to achieve sufficient draft.
I might try this in about a year's time.
|
|
cab
New Member
Posts: 33
|
Post by cab on Mar 8, 2019 5:30:12 GMT -8
You mean like: www.youtube.com/watch?v=gKZJFOsDLmUThose down draught gasifiers must have very high particulate emissions with the double vortex constantly stirring the ashes up like that. Perhaps the extremely high temps and the turbulence lead to more complete combustion. Whatever the reason, they don't seem to have an issue from the test results I have seen. I should think the total, overall emissions are the important metric.
|
|
|
Post by Vortex on Mar 8, 2019 6:13:41 GMT -8
Now I come to think about it... Maybe, just maybe, there's a way around the necessity to have a downdraft gasifier run in updraft mode in order to achieve sufficient draft. I might try this in about a year's time. There was a video I saw on youtube a few years ago, of a batchbox with a downdraft chamber underneath with a glass front, showing it switching from rear port to downdraft. Was that one of yours Peter? I can't seem to find it now. It was German or Dutch I think, there was a radio playing in the background, and the stove was in a workshop.
|
|
|
Post by peterberg on Mar 9, 2019 5:25:21 GMT -8
There was a video I saw on youtube a few years ago, of a batchbox with a downdraft chamber underneath with a glass front, showing it switching from rear port to downdraft. Was that one of yours Peter? I think I know which one you mean Trevor. It was Dutch, by a guy called Michel who left the scene 5 or 6 years ago. The batch box sported a slit in the floor and a downward extended port. By blocking the higher part of the port the flames were forced to go down through the slit, to the back and up the riser. This setup wasn't succesful by the way, I measured it and it turned out being quite a bit dirtier as compared to the straight batch box rocket. No wonder why you couldn't find that particular video by the way, Michel left a Dutch ecological forum with quite a row and took all his videos offline.
|
|
cab
New Member
Posts: 33
|
Post by cab on Mar 9, 2019 7:09:20 GMT -8
Interesting that most, if not all, of the wood gassifier boilers on the market are downdraft. Also interesting that the Wittus Twinfire woodstove, a downdraft gassification woodstove, took first Prize at the 2018 Wood Stove Challenge. Judges said, "Great performance on particulate matter, CO, efficiency and safety." Other comments were "This stove impressed both the Brookhaven National Lab and the Masonry Heater Association testing teams with ultra-low carbon monoxide numbers in the single digits under some conditions, and ultra-high efficiency. In the 2014 contest, the Twinfire had the second highest overall efficiency, at 74%, and one of the lowest emission rates on a test run. The Twinfire has consistently finished near the top in the annual wood stove competitions. I have no affiliation, just noting that a downdraft wood burner can indeed have high performance. Food for thought. Picture below:
|
|
|
Post by Vortex on Mar 9, 2019 9:34:19 GMT -8
There was a video I saw on youtube a few years ago, of a batchbox with a downdraft chamber underneath with a glass front, showing it switching from rear port to downdraft. Was that one of yours Peter? I think I know which one you mean Trevor. It was Dutch, by a guy called Michel who left the scene 5 or 6 years ago. The batch box sported a slit in the floor and a downward extended port. By blocking the higher part of the port the flames were forced to go down through the slit, to the back and up the riser. This setup wasn't succesful by the way, I measured it and it turned out being quite a bit dirtier as compared to the straight batch box rocket. No wonder why you couldn't find that particular video by the way, Michel left a Dutch ecological forum with quite a row and took all his videos offline. Yes, that was the one. It was really bugging me that I couldn't find it again, but that explains it, thanks.
|
|
|
Post by coastalrocketeer on Mar 9, 2019 12:27:33 GMT -8
I suspect that downdraft being able to run “cleanest” has to do with it being easier to achieve the 3 T’s to completion when forcing the combustion gas stream to go opposite the direction that it’s freshly heated gasses (and their embodied heat) wish to travel, and thus creating a super concentrated heat zone where the extreme temp shortens the time requirement sufficiently, in a zone where there is also sufficient turbulence induced.
This thought would make sense with the results seen with the latest iterations of Peter’s DSR II design, concentrating heat absorption in the zone immediately before the restriction, (especially the roof and tops of the walls, absorbing and re-radiating heat from those gasses in their hottest state) and inducing turbulent mixing at the same time.
My expectation is that a “top of the box” restriction will always perform better than the same restriction at the bottom of the shoebox, and that the smaller surface area in this extremely heated zone, will balance with sufficient space for mixing time to an optimum balance... too much surface area/volume/uninsulated mass in this zone will greatly reduce temps achieved and cleanliness of combustion, while too little surface area, distance traveled, and thus mixing time will also reduce cleanliness of combustion.
Bear in mind that I say all of this knowing little to nothing about down-draft combustion systems and their design, so it may not be relevant to them at all, and additionally, I may be entirely off base on any or all of it... just a notion/hypothesis, waiting to have holes shot in it.
|
|
|
Post by andrey on Mar 11, 2019 19:07:57 GMT -8
Peter have you ever tried a secondary chamber underneath? A heater like the Walltherm need to be heated up in updraft mode for half an hour in order to create enough draft. During this heating up it burns as clean or dirty as a bog standard box stove. My goal has been a system that burns clean within 5 to 8 minutes, no more. This way the clean burning period in every run is as long as possible. Long ago I tested a Walltherm, twice. Maybe I could take this discussion to a new thread and dig up the results? " FAQ - Frequently Asked Questions:When do I switch to TwinFire mode?...It is absolutely necessary to have temperatures of about 1200 °C somewhere in the stove. This will be the case after preheating for at least 30 minutes. Give the stove and the chimney the necessary time to warm up the complete system. If it is really cold outside, it might be necessary to preheat up to 50 minutes to warm up the complete system."
|
|
|
Post by Vortex on Mar 12, 2019 3:03:40 GMT -8
Wow. I wonder if any of their efficiency numbers include that part.
|
|
serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111
|
Post by serg247 on Mar 12, 2019 3:10:03 GMT -8
Теперь я подумаю над этим ... Может быть, просто, может быть, есть способ обойти необходимость запуска газификатора нисходящего потока в режиме восходящего потока для достижения достаточной тяги. Я мог бы попробовать это примерно через год. Несколько лет назад на YouTube я увидел видео с коробкой, в которой находилась камера для нисходящего потока со стеклянной передней частью, показывающая, что она переключается с заднего порта на нисходящий поток. Это был твой Питер? Я не могу найти это сейчас. Я думаю, это был немец или голландец, на заднем плане играло радио, а печь была в мастерской. donkey32.proboards.com/post/32340/thread
|
|
|
Post by Vortex on Mar 12, 2019 6:42:36 GMT -8
I see now that your were referring to the same stove. At the time I searched google and youtube for "R177DXL Michels." but didn't get any results, so was not sure what you meant.
|
|
serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111
|
Post by serg247 on Mar 12, 2019 6:55:33 GMT -8
Michelle deleted his blog and video. But, in my memory a lot remains.
|
|
graham
Junior Member
Posts: 74
|
Post by graham on Mar 16, 2019 7:51:50 GMT -8
My downdraft gasifier stove has pm 2.5 quoted only in gasifier mode. Minimum time, 20 minutes to achieve that.
There's very little ash in the bottom chamber.
|
|
|
Post by Vortex on Mar 16, 2019 9:52:58 GMT -8
So where does all the ash go?
|
|
graham
Junior Member
Posts: 74
|
Post by graham on Jul 14, 2019 3:38:46 GMT -8
It stays in the top chamber.
|
|