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Post by martyn on Feb 4, 2023 11:56:51 GMT -8
The last couple of burns (not recorded) were not very good, I thought it might be because the vortex slot was 3 inches deep so I scalloped out the fire box roof.
There are just so many variables, it seems like there are so many things to try.
I have a large filing cabinet in my shed that the stove will easily fit in, so that is on the agenda.
I dont need stored heat for my party house, just radiant heat and a cooking plate, so that is the target.
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Post by Vortex on Feb 5, 2023 3:01:07 GMT -8
Since adding the secondary air through the sides of the port my port is now 2-3/4" / 70mm deep. I remember being worried about it at the time as 2" is thought to be the maximum, but with the secondary air shut off it didn't seem to make any noticeable difference to the testo results as compared with the 2" deep port.
The downside I found with using more air was it carried to much heat through the mass and out the chimney, but as you are not trying to store heat that wouldn't be an issue for you.
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Post by martyn on Feb 7, 2023 11:33:18 GMT -8
It was fun trying to sort out my over-fueling while re loading my hot fire box, I seem to have found a way around that but I need to build a fresh stove with fully adjustable air.
I dont like the overall look of the vortex as much though, it seems more dark red and it really stays right at the back of the afterburner for most of the time. There are two small independent vortex in the top corners and these will extend right up to the glass but the main vortex stays at the back.
If I have fully adjustable air, I should be able to adjust all the setting more accurately rather than stuffing a rag in a hole, then hopefully I will get better results.
It would also be nice to see it working in the dark.
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Post by Vortex on Feb 8, 2023 3:21:28 GMT -8
Great work again martyn. Looks like a really good adaptation for the dedicated cookstove, did you try that one with the glass over the firebox door? IIRC at 400*C the air expands about 4x so the 30% csa secondary would be delivering the primary equivalent of about 7.5% csa 02 into the afterburner. (10mm x 233mm = 2330 / 7855 = 30% /4 = 7.5%) |
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Post by martyn on Feb 8, 2023 7:38:35 GMT -8
That is an interesting equation, I dont have any accurate way to measure the actual air entering the afterburner.
Yes it runs fine with 20-30% primary air, I think I have tried most options of air supply but I have not filmed everything as yet
I have an idea to fit a removable tray with a perforated bottom that will sit on the base but can also be lifted up to a mid way position and expose the perforation or be use to burn half loads in the top position.
I have an old filing cabinet that the stove fits in nicely to provide a bell, so that is next on the list.
I think I will also change the top of the firebox over to cast iron, I have a 8” square skillet with tapered sides that I might be able to fit in an inverted position.
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Post by martyn on Feb 9, 2023 6:22:40 GMT -8
Well todays experiment went better than expected, I was thinking the vortex flame looked a little loose, the 10mm gap was in fact 25mm for the test run!
I think there are air leaks all over the old cabinet and I would like to raise the stove up another 8” , in fact I wonder what the effects of a 12” riser would have?
Even with this basic leaky set up, I though it went very well for such a small core and only about a half full fire box!
The fact that the core is still functioning is a result in its self, proving the durability of vermiculite, wether it would still be suitable for a bigger more powerful core I dont know?
I still have so many ideas to test out but my wife is getting a bit frustrated, complaining I am not doing my household duties!
So there may be a lull in further testing……
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Post by Vortex on Feb 9, 2023 11:52:33 GMT -8
Brilliant  The 1" / 25mm secondary air opening around the sides of the port would be 74% csa, but your secondary air inlet on the front is only (152mm x 20mm) 3045mm2 / 7855mm2 (4" csa) = 39% csa /4 (thermal expansion) = approx. 10% csa secondary air - which seems to be about right looking at that. |
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Post by martyn on Feb 9, 2023 12:59:26 GMT -8
I am finding those figures difficult to get my head around as surely that quote must effect any pre heated secondary air figures… ie Peters batch box pre heated secondary air must be very small amounts, in a roof channel the air could be well over 500c?
In any case I dont think the actual air is reaching 400c. The flame coming up through the slot is probably 450-500c and the little bit of vermiculite were registering 400c but they are obviously being cooled by the incoming air so I assume the air is actually quite a bit cooler.
The Skamol VIP-12 HT I am using is 25mm thick and offer maximum service temperatures of 1250°C (2282°F).
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Post by Vortex on Feb 9, 2023 13:30:37 GMT -8
Yes that's a worst case scenario, as the larger the secondary air supply the more the available heat is going to be diluted in it. It was Peter who actually made me aware of it - I knew air expanded about 4x at 400*C but it didn't click until he said that it meant the same volume of heated secondary air would be supplying about a quarter the O2 of the same volume room temp air.
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Post by martyn on Feb 9, 2023 14:00:01 GMT -8
I will have to study that a bit more, it does appear that the hotter air has more effect but without being able to measure the temperature accurately it will be difficult to find the very best temperature.
I really want to try two 20mm holes in the back wall directed at the center of the vortex, I want to try this for effect but I think i would need to really super heat the air to get a blue flame.
Another thing would be an air wash in front of the afterburner window.
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Post by Vortex on Feb 10, 2023 2:57:51 GMT -8
I tried two half inch / 12mm holes in the middle of the back wall early last season, IIRC it messed with the vortex somehow, maybe pushed it forward - interested to see what the larger ones do on yours.  |
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Post by martyn on Feb 11, 2023 8:26:45 GMT -8
There are a few people asking me to try out rounding the corners in the afterburner so I did three experiments.
First one I went to town and used four, one inch triangles in the corners for the full length, that resulted in a fountain like in Peters DS3.
Next I added a splitter in the middle, hanging from the ceiling, now we had two elliptical vortexs, not very nice.
I then reduced the corners to just half inch, much better but still no improvement over a square.
Finally I tried no corners but left the splitter, no better than a aquare!
Next I would like to try tapering the afterburner, so it gets bigger at the exit, maybe 4” x 7”.
I also though about keeping the afterburner square but angling it up to achieve a better perspective.
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Post by Dan (Upstate NY, USA) on Feb 11, 2023 14:19:28 GMT -8
No vids?
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Post by rubenn on Feb 12, 2023 4:12:21 GMT -8
Hi guys!
Amazing information here!
I've been searching for quite a while to find the latest updated sketchup file of the vortex, but can't find it.
I'm planning a rocket cookstove and want to have a look at the vortex type, to see if this is an option with the materials I have.
If someone could add the file again, that would be amazing.
Grts
A young experimenter
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Post by Vortex on Feb 12, 2023 5:27:10 GMT -8
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