Vortex Stove

[Vortex]

Hi Pat,

It was just a little test hole for curiosities sake, I'll think I'll wait till I have the test bed stove setup to check out a proper EGR port in the throat.

V-Port it is then. A changeable modular insert is a good idea. I wouldn't think you'd need worry too much about insulating it from the surrounding masonry though, as the throat is the hottest part of the stove. You may even cause the insert to cool down quicker during the gasifying stage when you could be benefiting from the stored heat radiating there.

My original stove which is a 6", was designed to be made from the standard fire brick size of 9" X 4.5" X 3". You can see the layout in this picture:

www.vftshop.com/images/others/Stove/vortexstove3.jpg

Internal dimensions are approx 12" wide X 13" high X 16" deep for the 6" w/ CSA of 28. (original depth was 18.5", later shortened to 16" by adding 2.5" slab in the back of the firebox)

So a 5" system with a CSA of 20 would be roughly: 8.5" X 9.5" X 11.5" ?

A 7" System with a CSA of 38 would be roughly: 16" X 17.5" X 21.5" ?

An 8" just comes out ridiculously huge.

EDIT: Sorry these sizes are wrong. The corrected sizes are in a post below.

[patamos]

Hi Trev,

Thanks for doing the math. WIth the 9" x 4.5" x 2.5" bricks i have here (and some 13.5" long) i'd be inclined to build a 5" CSA system with a 9" x 9" x 13.5"(deep) fuel chamber.
With the relatively greater depth maybe set the throat back a little. Maybe not ?

[labalme]

Nov 19, 2015 15:05:08 GMT -8 Vortex said:

So a 5" system with a CSA of 20 would be roughly: 8.5" X 9.5" X 11.5" ?

A 7" System with a CSA of 38 would be roughly: 16" X 17.5" X 21.5" ?

An 8" just comes out ridiculously huge.

Hi

I have been experimenting with trying to get a vortex running in a vertical flue riser adaption for a metal wood burner. No success so far.

I really like the compact concept of your stove and have now got together the materials to build it. "Imitation is the best form of flattery"
I will be heating a 42 square meter room. I have a 7" chimney with very strong draft. I plan to use the stove cook plate as the base of a white oven and to make a bench bell. I would like to double skin heater for extra fire security.

I have 3 questions.

1) How have you scaled up your dimensions for 7" (18cm) system?

2) Is there any advice regarding bell sizes for a scaled up version?

3) As anyone tried using the vortex cook top shape to redirect the burn from the top of a metal wood burner into a brick bell? 

Thanks

Peter

[patamos]

Hi Peter,

Sounds like some interesting experiments. I'd be interested in seeing pics of what you have tried so far.
I thought about creating a sort of heat riser above the throat on a 45 angle towards the rear.
I can't see why that (or a vertical one) wouldn't work, so long as there are no bottlenecks in the flow of gasses.
Then again, maybe the behaviour of the secondary burn would shift so much as to throw the general behaviour off kilter…

I'm not sure what you mean by 'metal wood burner'. I'm guessing a slab of metal from the top of a metal bodied stove(?)

Anyway, if you flip back a page you can see video of the vortex successfully feeding a double brick bell.

Also, if your oven use is not too frequent, the fire box makes a great post-fire oven.

[labalme]

Hi Patamos

I mean a standard all metal wood burning stove. I want to improve my existing wood burning all metal heavy topped oven.

I have already asked about vertical vortex in my post "vertical mass heater". The argument re negative pressure zones started me thinking on how to spin the vortex without a throat. Have tried to create a spin using a helix former works to a degree but not very powerful. I am afraid no pics as I am still thinking. Maybe I need to speed up the gasses in the flue. I have been thinking maybe need to constrict the path within the helix, but I have not got round to building yet.

The vortex cook top shape made me think that it might be possible to create a further burn on top of my metal oven before passage into a bell.


I will build a new "masonry" stove to heat a large stable room we have in the French Alps.

I like the looks of the vortex stove aesthetically and functionally it has the heat delivered low down, without need of a riser, this I think makes sense. As this stove seems to be well documented i am very inclined to build this for heating my stable room. The alternative is the Walker riser-less stove, but this seems less well documented.

I want to use the full power offered by the existing 18cm insulated flue. If anyone has already built a 7" vortex I would love to know. I am a concerned to get the thermal mass right. Hence my questions.

Peter

[Vortex]

Hi Peter, I'm not sure exactly what you mean by "get a vortex running in a vertical flue riser adaption for a metal wood burner", do you have any pictures or video?
Metal is OK for the door but it's not the material for the body of the stove. The design depends on the refractory masonry to store heat and reflect some of that stored heat back into the fire, this enables the later slow burn gasification stage. Also the intense heat will burn steel pretty quick.

The primary air port position and size is very important, the venturi effect there drives the rocket, generating an inferno in the kindling and smaller fuel in the front of the fire, heating the firebox and fuel to the point where you can shut the port almost right down and it will gasify the large fuel at the back in a beautiful long slow burn.

The sizes I gave above are just rough. I worked them out by using the percentage area difference of the 5" and 7" CSA, and made the dimensions based on those percentages of the original. Not sure if that's the best way to do it.

Edit: Sorry, you posted your reply while I was writing mine.

[labalme]

Nov 22, 2015 3:29:14 GMT -8 Vortex said:

The primary air port position and size is very important, the venturi effect there drives the rocket, generating an inferno in the kindling and smaller fuel in the front of the fire, heating the firebox and fuel to the point where you can shut the port almost right down and it will gasify the large fuel at the back in a beautiful long slow burn.

The sizes I gave above are just rough. I worked them out by using the percentage area difference of the 5" and 7" CSA, and made the dimensions based on those percentages of the original. Not sure if that's the best way to do it.

 

Thanks Vortex and Patamos.

My existing heater project.
I will continue to "play" with the idea of a secondary burn at the junction of flue and metal wood burning stove. I can't help feeling that there must be an elegant solution to burning the exhaust gasses of old style wood burners.

My new build vortex stove project.
I guess i will scale the dimensions using CSA ratios to 7" and build the core to this with an "if it looks right it probably is" white oven over the vortex cook top. Then make the bench bell adjustable. I note Patamos had 5 sq. m of bell.  7" scaled is 6.9 so, as mine will be doubled skinned, I hope 6sq.m. will be a good starting point.

Vortex could you expand on your comment above. What dimensions for primary air are you using? Would a variable air intake built into the door be advisable? I guess this would also act as a door wash.

I note the discussion regarding secondary air and wonder if a gate valve controlled intake as used in the Missouri heater would be useful. This could be preheated by running the pipework through the bell.

I have questions about casting. You are using chicken wire. How is this arranged? Is there any point in folding the mesh to get form stability?
Using chicken wire do you add aggregate or is it possible to just use refractory cement? The sections you label as concrete - is this bog standard portland mix and if so to what ratio?

Thanks

Peter.

[Vortex]

Hi Peter, You mentioned wanting to build the stove for a 42 sq meter room?
I have my 6" CSA vortex stove in a 42 sq meter cabin and it's plenty big enough even for the coldest winters.
This stove works best when run on a full load, so I would rather have a 6" running full tilt than a 7" half empty. My firebox has been shortened to 16.5" from 18", so it can take more, so is a 7" really necessary?

The primary air port is 1-1/4" / 32mm up from the bottom of the door, and is 5" / 127mm wide by 1-1/8" / 28mm high. It has sliding covers that come in from both sides and meet in the middle.
There is no need of airwash, the stove burns so hot any slight smoking of the glass that happens at startup is burnt off as soon as it's up to temperature.



My secondary air supply is hidden in the door design, there's a 2mm gap between the top of the door and the door frame, it acts like a P-channel, allowing air through and heating it between the hot metal surfaces before delivering it just in front of the port, so it mixes with the gases there. I plan to experiment with other ways of doing it when I have my workshop test stove setup.

I only used chicken wire in the throat casting because it's only 2 inches thick. It was just one flat piece and the casting has never cracked. The castings are all made of Castable Refractory Cement, which comes as as a 2 part mix of aggregate and some kind of cement. The details are on the first page of the thread in this post: donkey32.proboards.com/post/6325

The bell sections labelled as concrete can be made of any normal concrete mix, but if you're making a compact version like mine it's worth using firebrick because it's extra density gives it a much better thermal mass - but they're expensive.

[labalme]

Nov 22, 2015 15:46:51 GMT -8 Vortex said:

Hi Peter, You mentioned wanting to build the stove for a 42 sq meter room?
I have my 6" CSA vortex stove in a 42 sq meter cabin and it's plenty big enough even for the coldest winters.
This stove works best when run on a full load, so I would rather have a 6" running full tilt than a 7" half empty. My firebox has been shortened to 16.5" from 18", so it can take more, so is a 7" really necessary?

Hi Vortex

Yes I had thought of using your 6" dimensions. But I have this really expensive insulated super efficient flue 18cms. We are in the high alps and it gets seriously cold for 2-3 months. However i will think on it. Not planning to start till spring. The 7" temptation may just be too much. The stable is on the ground floor of an old wooden barn alpine farm house renovation. We will start on the upper floor barn soon so extra heat will not be wasted.

I guess you are in Ireland as you seem to have used Dincast.

Thanks for your input.

Peter

[Vortex]

Hi Peter,

Yes, I'm in Ireland. Not as cold here in the winter as where you are but the damp can make it feel like it quite often.

I realised I made a mistake in those calculations of the scaled up firebox sizes - math is not my strong point. Looking at the corrected sizes I think a 7" will be a good size for your needs. The sizes I got before felt to big because they were.

Scaling up from a 6" to 7" CSA gives a scale factor of 1 over 1.16
So a 7" CSA firebox comes out at 14.8" High by 14.2" wide by 18" deep.

5" gives a scale factor of 0.83 so the firebox comes out at 10.6" High by 10.2" wide by 12.9" deep
8" gives a scale factor of 1.33 so the firebox comes out at 17" High by 16.3" wide by 20.7" deep

[Vortex]

Hi Pat,

The night before last I got a 6 and a half hour burn, on one load of fuel! The longest I've ever had. The temperature in the house went up to 28*C/86*F. I had to door the open for 2 hours to cool it down. For some reason the stove was gasifying better than usual.

I could only think of 3 things I'd done differently to normal- I'd used a large knot of Monterey Pine in the back of the firebox with a few bits of Holly wedged in around it. I also used the poker to make a hole down through the ash-bed in front of it, and closed off the primary air completely when the stove got up to temperature. The ash-box is quite well sealed but a small amount of air does leak in to it around the steel cladding. The fire burnt differently after the primary air was shut down. There were jets of white flame coming up from the hole I'd made through the ash-bed, and slowly dancing disembodied flames licking up around the throat. Seemed like it was never going to stop, reminded me of those propane fake wood fires I see on TV.

So last night I tried to repeat it, but I only used about three quarters the amount of fuel as I didn't want to overheat the place again. The fire behaved just as it had the night before, except it lasted about 4 and a half hours.

It got me thinking about secondary air at the base of the fire (instead of, or maybe as well as in the throat/riser). I might try something there like a P-channel, as this really seemed to improve the gasification. Any thoughts?

[labalme]

Nov 24, 2015 9:01:41 GMT -8 Vortex said:

Hi Peter,
 Looking at the corrected sizes I think a 7" will be a good size for your needs. The sizes I got before felt to big because they were.

Scaling up from a 6" to 7" CSA gives a scale factor of 1 over 1.16
So a 7" CSA firebox comes out at 14.8" High by 14.2" wide by 18" deep.

5" gives a scale factor of 0.83 so the firebox comes out at 10.6" High by 10.2" wide by 12.9" deep
8" gives a scale factor of 1.33 so the firebox comes out at 17" High by 16.3" wide by 20.7" deep

Thanks

  OK  7" it is then!

One more question.
I want to build in tweakability.
I have been looking at casting and note Patamos saying he used cardboard forms. Any reason not to use thin plywood form with mix of fire cement, sand and aluminum oxide casting grit and water glass plus maybe glass fibre to reinforce. The ply wood form to be burnt away. Glass fibre should expand at roughly the same rate as sand so maybe less cracking. The casting could then be formed in place. Also where replacement is necessary could make an easy method to cast in situ.

I have spent a good few weeks in your Emerald Isle. My first experience was in Bantry - 10 days of blistering sunshine not a cloud in the sky - a truly amazing experience.  My daughter in law comes from Dingle.

Cheers

Peter

[patamos]

Hi Peter,

To clarify, I used cardboard because i had some dense 3mm thick curved stuff laying around that was perfect for shaping the curved trip wires (by lapping the seams) that i wanted to build into the throat.

Plywood, by design, will be useful for other aspects of formwork, but shaping curves will not be easy.

Regarding system size. The fire box i built was 13.5" wide by 13.5" tall by 18" deep. This is slightly over the dimensions Trev used. I did this only because it better accommodated the dimensions of bricks i have here.
The system pulls great, which suggest there is some leeway in dimensions. But then, i also have over 20' of vertical flue draft to pull things along.

I hope you enjoy the vortex-building process as much as i did

[labalme]

Hi Patamos

I have used ply in boat building. De laminated ply can be used much the same as veneer. Several layers held together, there are a number of ways to do this - staples glue etc. I have used to make difficult shapes with GRP microfibers. The other material I have used is soaked hardboard which bends super easy and is stiff when dry.

The refractory recipe is from a guy on U tube who is making "FIREBRICK" for smelting. He just tamps the mix which made me think it could be would be good for casting in situ. www.youtube.com/watch?v=

Yes I am really itching to get started on the build. I have read a lot about different heaters. I think the Vortex wins on aesthetics. Functionally having the throat forward is neat.

My insulated flue is 13+ meters as it goes to the ridge of a 3 floored steep roofed alpine farm house. I didn't build it was there when we bought the house..it would have been extremely expensive. Wicked draft.

[patamos]

Ahh, boat building,

No doubt you have the ability to create what ever shapes you are envisioning.

Yes that mix sounds interesting.

When i hear that masonry stove builder's like Alex Chernov and Lars Helsbro are achieving very high combustion efficiency... I think this vortex design has the potential (if not already there) to be as efficient as the latest batch boxes.
The shape is right. The throat is in an ideal place for optimizing viewing aesthetics and pumping heat into the room which enhances 'quick heat' harvesting efficiency.
Peter van derBerg's experiments with a rocket siphon off the back of a batch box were very informative, and much of that investigation of throat/riser dynamics can be carried on with ease of modular throat replacement in this application.

Exciting times.