Vortex Stove

[Vortex]

Mar 3, 2021 0:35:30 GMT -8 martyn said:

My stove is built with 30mm cast walls and has two inches of insulating CF so quite different to Trevor’s!

So I was up early this morning to use up my basket of wood that has been in the airing cupboard for two days sitting on the boiler.

95% 95% and yes is was a good burn, there was very little wind and that might of played a part too but a better vortex and very hot burn.
I also noticed the chimney temp has risen to around 75c however I am still not quite happy with theses new setting as it was a fast burn going from match to coals in one hour.
I will try again with less air next time.

Mine is 95% for the whole length of the top chamber, I think that will behave quite a lot different than two 95% ports.

I seem to be getting longer slower fires with this setup. The less resistance there is the faster the gas flow, the hotter the exhaust temps and the shorter the burn time, so it sounds like you need more.

You could setup a drying rack above the stove to dry out the next batch of wood with each burn.

Forgot to put the filter in the testo probe last night so the testo didn't record anything. I was in late and distracted cooking and didn't notice till half way through. Looked like a really nice burn again though, beautiful vortex. I'll run it again this evening.

[martyn]

Good idea about drying the wood.
My top chamber and exit are in fact just a tunnel with an gentle uplift at the end but outside of the exit.

I feel I have to step back and check out my original setting, that was 95% top box (i think) and only about 65% exit because i am not actually sure if I have ever had a better burn.

Of course my idea of a great burn is only based on visual effect and longevity of the burn but that is fine for me.

If I have a main issue it is the extended coaling stage as I dont find that an attractive aspect for my personal use.
If I was to rebuild that is one thing I would pay a lot more attention to, as it stands i have an idea about speeding up this stage with an electric fan.

The ceramic glass delivers such an even temperature into the steel top plate it make a superb cooking surface and the average temperature of around 250- 290c is perfect
The heating performance is also great but I have tried adding wood on top of the coals and it does not work very well with a smoky glass and then a raging fire for a short time and then even more coals ha ha...
Obviously I have not gained enough experience to understand all the possible permutations so I will keep plodding along .....

[Vortex]

What works best for you is what you should do. What looks best to me is luckily always also the best on the testo so long as the vortex stays in the afterburner.

To speed up the coaling phase, there's no need of a fan, a very small amount of bottom air works wonders and is a clean burn with a steep V-shaped firebox floor. It only creates more CO. if there are holes through the coals into the ash-box, so long as they keep falling in on themselves CO. stays low.

It's hard to re-load without creating a dirty burn, it's a bottom lit fire which are a lot harder to get to run clean. The best results I've had were putting a large log on top of hot bed of coals and then open up the air a bit. That works OK, get it right and it doesn't smoke up the glass, on the testo there's a very short CO. spike then straight back down again.

This evening I did the third run with this setup and it was the best so far:

[serg247]

When reloading, move the coals with logs to the port so that the logs burn from one end, passing gases through the coals.

[Vortex]

I see that should work with a BBR or DSR2, but how do you do that with the port in the roof? You'd have to shovel out all the embers from the firebox, load up with a new batch of wood and then shovel the embers on top.

[lums]

Good evening,
Have you optimized combustion by playing with the air inlets?
the carbon phase is not on the graph?

[Vortex]

The best I've found for this setup is full primary air until after the peak of the burn, when the vortex starts to turn back to a palm tree shape, then reduce primary to about half (10% CSA), so the vortex comes back full but stays in the afterburner. Then later again when the vortex starts to turn back to a palm tree shape, reduce it to 6% CSA primary air and open a tiny bit of bottom air (0.5-1% CSA). Leave it like that until the last embers are out and then close everything.

I dont know how you measure carbon phase, it's not in the testo options anyway.

[lums]

sorry but the translator can give inconsistencies .... this must be taken into account.
I meant the embers phase.
the end of combustion.
but you answered the question.

[Vortex]

Oh, you mean the coaling phase. It starts around the time the CO. begins to rise again and O2 is 13-14%.

[martyn]

I have been running the vortex stove for a few weeks now, it has been fun and entertaining for my friends too.
However I have decided to take it apart at least for the time being as the design does not really suit my needs.
I love the effect and it does a great job at heating my space but I don’t like the long coaling stage and I can’t find a method to re stack fuel without smoking up the glass and over fueling.
I am going to re in state my old stove, for the summer anyway, as it is easy to run at lower temperature and easier to regulate cooking temperatures.
It has been an interesting ride and a bit of a challenge to deviate from Trevor’s design but I have learnt a lot and I have plans to rebuild it in the Autumn.

[Jura]

Mar 21, 2021 13:37:30 GMT -8 martyn said:

but I don’t like the long coaling stage and I can’t find a method to re stack fuel without smoking up the glass and over fueling.

Has your stove been airtight enough thus allowing uou to stifle/smother embers?

[Vortex]

Thanks for the update Martyn.

It is hard to refuel without getting the glass dirty, I don't think the stove design is any less capable of dealing with it, just the glass makes it more obvious that refuelling a hot stove is a dirty business. I mostly I run it on one fire a day, maybe two in very cold weather, so it's not a common problem for me.

The coaling phase in my stove is of a normal length - same as you'd get in a typical metal box wood stove. I've had that premature coaling phase happen under certain conditions on many different stoves, it mostly seems to be air flow related, so should be fixable for you.

Normally the coals on top get burned up as the fuel below goes through it's flame phase, when combustion is too fast this process gets disrupted and you have too many coals for the fuel below to consume and the fire gets choked up and berried in them. Things I found helped to avoid it were:

*A more diffused air supply, (so instead of blowing on one spot it is spread out over a much larger area).
*Laying the larger pieces of wood at the bottom so there are some air gaps around them.
*A small amount of bottom air during the latter part of the burn.
*A more restricted system so the combustion is slower.

[martyn]

I wonder how much difference my method of construction might of made in comparison to your design, is was interesting to see that the 30mm slabs where still in one piece although the back one does have a few hairline fractures, the sides and bottom were like new.
The glass under the shelf was still in tact although totally opaque and pitted, the vermiculite shelf has also got two hairline cracks but still usable, the vermiculite firebox sloping sides are still perfect.
The insulating bricks are like new, I enjoy working with those bricks as you can cut them with woodworking tools to a very accurate size and shape them to any contour.

I used 50mm ceramic board as the basic outer shell and that is all reusable but i wonder if one could build the whole stove from fire brick and only insulate the afterburner.

My old stove is now back up and running, it does use a vortex design but inside a 30” high heat riser and i take your point about no visible evidence of smoke or overload but it is like a dustbin and will burn any odd bits of wood i can fit in the firebox.

I dont think i could of used your vortex design (in my format ) throughout the summer in my partyhouse as it would just be to hot to be near enough to cook on.

I did get the vortex stove running sweetly most of the time over the last few weeks but I found it only liked very dry and consistent wood .... if anything that was the answer to many of my earlier issues .

[Vortex]

You had more insulation than me so it's possible that could have contributed to the premature coaling phase problem. My stove only has 1 inch / 25mm insulation on the outside of the 2 inch/ 50mm thick side and rear slabs. It's more to stop the metal sides getting too hot and burning people and to stop the core cooling the firebox than anything else.

I've noticed the less well tuned the top chamber is to the rest of the system, the more fussy the stove is about wood quality and fire laying. I'm now running with a 100% CSA top chamber (more of a channel), but was not satisfied with the vortex so have been running it with the exit port back to 78%, that has improved the vortex. The weather is too mild now for full loads so I've stopped running the testo every day, it's nice to not have to listen to the irritating buzz every evening. I'll hopefully have the money to get it re-calibrated before next season, and carry on with the top chamber experiments then.

[fuegos]

"I did get the vortex stove running sweetly most of the time over the last few weeks but I found it only liked very dry and consistent wood .... if anything that was the answer to many of my earlier issues"
with my limited experience this is critical. Occasionally a very resinous pine stick or a piece of oak that's not quite seasoned enough will result in overfueling. Also I've learnt that using bigger wood on the second load cuts down on this.This is with a riserless core that has the door open after loading for a few minutes so lots of air. I'm not sure if this has any relevance to this thread and it's purely anecdotal as i've taken no measurements.We baked today , firing the oven at 07.30 using about 10KG of mostly pine and now at 21.00 it's at 175 F .by this mesure i think it's a pretty efficient design. I'm looking forward to the final build on this .