Vortex Stove

[fruitbat]

Exciting stuff Martyn, keep us posted on further trials, hoping this iteration works out for you!

[recumby]

Curious where/how the secondary air is designed in this promising setup!

[martyn]

I do have some buid video, but I am on holiday at the moment, the last fire I lit yesterday, did seem to be overfueling but still no smoke out of the chimney.
Back home in a week, so back on it then…..

[Vortex]

Did the annual stove clean out a few days ago, was surprised how little buildup there was - cleanest it's ever been. Used to get an inch or 2 in a bucket, this year it barely covered the bottom - could have left it another year or even 2.

[martyn]

I have posted a few more experimental videos, here is the latest….

[Vortex]

Hi Martyn, I found the vortex formed best and burned cleanest when the rear of the port is as far back in the afterburner as possible. On my setup I have it slightly farther back than the back of the firebox with a sloped back and front to the port.

I believe what stops the overfueling on mine is the combined resistance of the 1.5 SA:V (surface area to volume ratio) top chamber, 1 CSA exit port, and contraflow labyrinth with 13 90 degree bends. If I was going to try it in your setup I think I would probably try a very wide low top chamber with a very high SA:V, the difficulty would be the transitions at the entrance and exit, as you cant just go from something very wide and low to something square and maintain the CSA.

Trev

[martyn]

Hi Trev, yes I was running the stove with the vortex slot right back as far as possible today, the slot was placed more forward because I was running the stove backwards at one stage as an experiment (that had mixed results) .

I had a very interesting progress this afternoon, I lit the fire at 1pm and tried out some new settings.
The fire was going for almost four hours and was re loaded at numerous stages of burn with varying types and sizes of wood.
I actually made the stove deeper than my previous versions a I wanted to try different positions for the vortex slot, it is now right back making the afterburner slightly longer than I have tried before!
So what I found is that as the stove gets hotter and hotter the vortex display gets smaller and smaller.
During my last reload, I offered in two large logs, they caught fire easily, there was no overfueling but the vortex remained very small and only right at the back.
The fire was raging and all the temperatures were sky high.
I assume that because the air supply is so hot as the V was almost full of coals, all the gasses were being burnt off before they reached the vortex chamber?
I have loads of video, it was a strange turn of events….

[Vortex]

Would like to see the video to be sure, but if I'm picturing it correctly then what I think is happening is too much air and in the wrong place. Startup is always the highest demand for air, as the fire progresses and gets hotter it requires less and less, also after the fire peaks it's gradually producing less volatiles and more CO. and so needs more air low down. Unfortunately I don't have a good video of it to show you, but it's quite a pronounced effect - almost completely shut off the primary and add a little bottom air up through the grate at that stage, and within about 30 seconds the vortex in the afterburner is fully formed again.

[martyn]

New video … 

[Vortex]

That's a nice way of doing it. What is the size and layout at the front of the afterburner under the piece of ceramic hob?

Looks like the resistance is all in the slot?

100mm system. 1csa = 7855mm2
exit slot: 420mm x 15mm = 6300mm2, 80% csa
exit slot perimeter = 870mm
slot SA:V = 2.77 (100mm system SA:V of 1 is 314mm, so 870 / 314 = 2.77)
The slot is only 80% csa though, so not sure how to calculate that correctly.

[martyn]

Trev, thee is just an empty space below the glass, 70mm at the moment but I will lower the glass 10mm every fire and see what happens

[Vortex]

Great, let us know how it goes.

[martyn]

I tried a 60mm gap, very similar results to a 70mm so I tried 45mm……

[Vortex]

That's looking great. More resistance gives a much more stable fire, but it's slower to start so you can use a bit more kindling. I use a blowtorch to light the top of the kindling, I find it a lot cleaner and cheaper than firelighters.

[Jura]

Oct 8, 2024 5:13:14 GMT -8 martyn said:

Maybe, just maybe, I have found what I have been searching for

Martyn my respectful hat tips to you.
Overfueling after reloading was the only hindrance that hold me back from constructing this setup at my allotment garden.
If the issue has been overcome I will finally put my palms on my tools...yupppiii