Vortex Stove

[Vortex]

The experimental stove in my garden







Rough dimensions of the present setup:

Firebox: 318H 308W 384D
Port: 50mm x 175mm /
Afterburner: 115H 230W 384D
Throat: 230mm x 67mm
Hotplate chamber: 65H 253W 672D

[peterberg]

Hmmm... that extra switchback with a slightly narrower throat might be the answer to the thermal overdrive.

[Vortex]

I've never had that problem on this design. I burn mostly log wood though, If I remember correctly you burn lumber scraps, which would be a lot more prone to it. Try it out, I'd be interested to hear how it goes.

[peterberg]

Yes that's true, I'd burn scraps almost exclusively the last couple of years. I prefer this fuel for testing because it'll push the combustion core to its very limits. When it is able to run consistently well that way it would do really excellent with larger fuel like log wood.

And no, I won't try it out, not for this year. I am toying with another idea that I would like to try in the coming autumn, based on the straight batch box configuration. Can't tell much beforehand, it might be one of those short-lived ideas.

[Vortex]

I tried it out last night with just small timber scraps. Stacked it with lots of air gaps, full primary air. It burned normally until about half way through the burn when it started to over-fuel. I gave it a prod with the poker to collapse the stack and it went back to burning normally again for the rest of the burn. Any stove would run away under those conditions, I was quite impressed with how well it coped.

[Vortex]

Tried it again last night but this time with just a 2" / 52mm 75% CSA throat. The burn was really slow to get started, couldn't get it to over-fuel no matter what I did. Way to timid for my liking.

[peterberg]

So if I understand correctly, the throat between the afterburn chamber and the cooktop chamber was 89% before and this time you shrunk it to 75%? It looks like the second restriction has a very strong influence on the working of the combustion core as a whole. Too narrow could mean it runs sluggy, too wide and it could run in thermal runaway part of the time. Tuning of the thing is essential as I mentioned before, the middle ground could be something between 80% and 90%, depending greatly on the draw of the chimney.
This is just a wild guess, I've never built this specific configuration before.

[Vortex]

That's correct, Peter. I think making that piece so it can be slid back and forward to adjust the throat size would allow it to be tuned to the rest of the system, fuel type, personal preferences, etc. Also if it could be slid back out of the way it would make the chamber usable as a small oven.

A piece of ceramic fiber board would probably be the best thing for the job. I've been using a piece of 6mm steel plate in my experiments, it spalls so much it almost covers the floor of the chamber in bits every burn. At startup it sounds like someone making popcorn.

[travis]

This looks like a neat project. Am I correct that there is no secondary air?
Its a good size, do you hope to add a mass bench/bell to see how it performs?

[Vortex]

At the moment my favorite configuration is with a small amount of secondary air coming in at the very front sides of the port, about 2% CSA. Would like to try introducing some more into different places in the afterburner, maybe from the back wall, 2 holes in the centers of the spirals. Weather's turned wet so I haven't been out experimenting much recently.

I'm just starting to cast some parts so I can try this setup out in my new stove that I built last winter. If you haven't seen it's on page 27. It's only 0.55 cubic meters in size but has 1050 KG of mass in it.

[Vortex]

Vortex Stove in Alaska

[Jura]

Am I missing sth or I can not see teh tertiary air channels in the setup from the first film.

[Vortex]

Sorry Jura, Didn't see your question until now.
I don't know anything about it. I came across it on Youtube. I would post a link to this thread in the comments but I don't have an account..

[Jura]

No Worries :-)! (as Kiwi says) I'm also dead busy and do not browse the forum frequently.
I thought it was your an acquaintance of yours.
I'll try to post a link to this thread in there.
BTW. as to my vortex cookstove project I'll pm you but after the weekend.

[Vortex]

Following on from my outside experiments last summer with an Aryan style afterburner on a Vortex firebox, I recently cast a new top and have been trying it out in the new stove.











Took me a while to get it running right, it's quite different on a large mass with many twists and turns in the channels, than on a straight up chimney like it was outside in my garden, but now I have I'm quite pleased with it. It's very easy to light and the top glass is a good 'truth-window', if the combustion is not clean it lets you know pretty quick.

The bypass has to be left open for about the first 10 minutes until the afterburner is hot, then it runs quite happily, but if you close it too soon it stalls. If I keep it I'll reconfigure the mass with less resistance which will solve that.

The top gap on here seems happiest set at around 75mm - which is 1 CSA. It needs more air than a standard Vortex top, so I'm running it with the door closed but not latched so there's a bit of extra air going around the edges, as well as full primary and secondary air. There is no tertiary air provision yet, it seems to be getting enough up through the front of the port.