The 3 T's of combustion

[DCish]

Boy is that a fascinating idea! Outer shell could be a metal 5 gallon bucket with "5 minute riser" style construction of ceramic fiber inside it. The round exit stub might be done with ceramic fiber and rigidizer. Tempting!

[satamax]

I have been thinking about this for a while, having a hyper insulated chamber after the firebox, in order to have more time to burn everything. This could be a solution. Other ways of mixing in there could ne invented too.

[Deleted]

Feb 3, 2019 11:15:19 GMT -8 Vortex said:

Yeah, the cone isn't necessary for our purposes, it's just there to slow the air down so it drops the dust.

On the contrary, the cone increases the speed of rotation to convey dust particles

by means of higher centrifugal forces to the outer wall at which they slide downwards.

Also the outgoing stream must travel significantly faster along the axis than the incoming one.

Without the cone it will very likely not work as desired.

[Berend]

A cyclone is also used in woodworking to remove (fine) dust. There is also a variant called "Thien baffle" which does not use a cone shape.
Matthias Wandel talks a bit about it on his website woodgears.ca/dust_collector/separator.html

[hof]

No need of cone. It is enough just to make two exit opens on the oposite sides.

[DCish]

Feb 4, 2019 4:51:45 GMT -8 hof said:

No need of cone. It is enough just to make two exit opens on the oposite sides.

The beauty of the design as posted by Vortex, as I see it, is that the inward-flowing gasses become the "container" for the outward-flowing gases leaving through the center. If the goal is sustained high temperatures, this could be a good, compact way to accomplish it. What it may lack (and this could only be really known through testing) is the intense mixing element that a 90 degree turn induces.

[Vortex]

Yes, the centrifugal forces should theoretically keep the denser unburnt gases spinning on the outer edge and only the lighter burnt exhaust gases should be able to move into the center and exit out of the chamber. I agree Brian, the designs lack of the sharp 90 degree turn after the port (double vortex) means it has a lot of mixing to make up for. That's why I think it would need to be quite small, so that the intense heat would keep the sides glowing red hot and the confined space would induce a lot of mixing.

Anyway I look forward to seeing the results of everyone's experimental models

[gadget]

So in theory, un burned carbon could be moved to the outer walls till they burn?

[DCish]

Not sure how much a difference the burned vs unburned would really make, though I wouldn't immediately rule it out. I think the primary effect is something already observed in stoves like Vortex has built, where once a vortex is induced, centrifugal force keeps the main stream at the outside, and as it curls inward on itself it is drawn more downstream by the flow. With the inner "exit tube" of the "dust separator" model keeping gasses from immediately moving toward the exit, the flow would be established toward the right of Vortex's sketch, and momentum would be likely to continue in that direction until the end of the tube is reached and flow is drawn backward down the middle of the vortex.

This is not entirely unlike the effect achieved by putting a 3/4" restriction around the outer edge of the flue path downstream of the initial double vortex in my last experiment. This keeps the initial vortex from being drawn downstream, and helps force the double vortices to fill internally before flowing downstream. In fact, this may be a superior method for inducing an external and internal vortex in that the 90* transition is preserved in this layout, along with the accompanying turbulence.

[hof]

www.stenovne.dk/englishcentrifugalcarburator.html


The two small figures (Narsissus and Ecco) are ceramic that just have beed burned.

They are not black, and they are burned all the way throug.

Ceramic will turn black if oxigen is missing for a short time.

So the temperature is o.k. and the mixing of gasses and oxigen has allso been o.k.



When the burning gasses enters the room from the throat in the floor just behind the door,

they can only leave throug the two hools located in the mittle of the sidewalls. (You see one of them at the right of the chamber)

Even gasses has a weight, and are affected by centrifugal forces, and when they enter this room, they are quit speedy

(thanks to Heikki´s invention of the throat), so they are forced into a spiral movement, where the latest gasses will keep up the heat of the first.

Furthermore - burned gasses are lighter than unburned gasses, so they come easyer into the mittle of this stream, and can leave the room

throug the two holes in the side.

The heavier gasses - those who are not burned yet - have to stay in the outher cirkel, untill they find som oxygen and can burn,

this way get lighter (allso because of the differens of temperature) and procide in the process.



This system functions allmost independently of the temperature of the stove, so the ordinary high contens of Co in the

beginning of a fire is allmost gone, and the overall average becomes extreemly low.



The system allso means, that you need less space to get a complete combustion.

Unless you put fare to mutch firewood into your firechamber, flames will not occured outside this "carburator".

That means, that you dont have to use anything else than one layer of ordinary bricks between your livingroom,

and the smokechannal just outside the bakeowen.

The temperature just outside the two holes will be less than the 572degrees Celcius that by time will damage ordinary bricks.

More freedom to build - mutch faster heat, if you come home from holliday to a real cold house, and a stove that dosn´t looks like Cassius Clay.



Remember:

This system we have used for allmost 20 years now.

You are wellcome to copy it, but please remember to tell where it came from.



Now we use it in our cookstoves to, but here it is located underneath the fireplace as an accessory

you can use when you don´t cook on the plate, and want a more clean burning and more heat to the buttom

of the cookstove. The "loss" is - no ash-dump, but that´s not so bad anyway.

In this case you off course have to have more than one damper to controll it.

In fact this is not so easy to explaine, but look out on my webpage for upcomming international work-shops,

where i whould love to tell you all about it.



Quistions are wellcome, but please - email me instead of phonecalls

[Vortex]

Feb 4, 2019 9:43:36 GMT -8 DCish said:

Not sure how much a difference the burned vs unburned would really make, though I wouldn't immediately rule it out. I think the primary effect is something already observed in stoves like Vortex has built, where once a vortex is induced, centrifugal force keeps the main stream at the outside, and as it curls inward on itself it is drawn more downstream by the flow. With the inner "exit tube" of the "dust separator" model keeping gasses from immediately moving toward the exit, the flow would be established toward the right of Vortex's sketch, and momentum would be likely to continue in that direction until the end of the tube is reached and flow is drawn backward down the middle of the vortex.

This is not entirely unlike the effect achieved by putting a 3/4" restriction around the outer edge of the flue path downstream of the initial double vortex in my last experiment. This keeps the initial vortex from being drawn downstream, and helps force the double vortices to fill internally before flowing downstream. In fact, this may be a superior method for inducing an external and internal vortex in that the 90* transition is preserved in this layout, along with the accompanying turbulence.

In my 'Aryan Vortex' setup the vortices appear cone shaped, with the narrow end of the cone at the farthest end of the afterburner from the firebox. This I think is because as the denser gases get burned the proportion of lighter gasses increases and the vortex spins in a tighter circle. I added a 3/4" restriction a few days ago, similar to yours Brian, and it does increase the effect: www.vftshop.com/images/others/Stove/restriction.JPG

Unfortunately it's not very easy to video, as the camera makes it look two dimensional, and the infra-red of the vortex comes out white, losing a lot of the true definition. Also the new Robax glass is already opaque from heat etching, and the samples promised by Neoceram have not materialised...

[gadget]

All this vortex talk reminds me of the Rangue-hilsch vortex tubes we use to use to test chocks on carburetors back in my early days as a mechanic. They plugged into shop air and put freezing cold air out one end and hot air out the other. No moving parts but it needed highly compressed shop air to work. Flow rate was very low. Temperature difference from each end was very high.

The cones where important in the design.

What is the hypothetical benefit for a wood heater? If its just to trap heat for combustion could that not be easily done with an insulated bell type setup? How about trapping carbon for later burning? Really good mixing? I like the idea of a carbon trap/reactor.

[gadget]

Is it safe to say that time is not on our side? So make sure temps are high and mixing is very good?

The good news is wood is a very forgiving fuel.

[DCish]

Feb 4, 2019 11:31:52 GMT -8 Vortex said:

In my 'Aryan Vortex' setup the vortices appear cone shaped, with the narrow end of the cone at the farthest end of the afterburner from the firebox. This I think is because as the denser gases get burned the proportion of lighter gasses increases and the vortex spins in a tighter circle.

I'm not sure how you would test to determine if the effect is caused by denser vs lighter gasses, or if it is just that the outer space is already filled, leaving nowhere for the gasses to go but inward and gradually more downstream as carried by momentum / centrifugal force. Either way, it is a visually pleasing effect, and in my mind serves to keep the heat focused in a smaller area, thus raising temps in that area / spreading the heat around less.

I added a 3/4" restriction a few days ago, similar to yours Brian, and it does increase the effect: www.vftshop.com/images/others/Stove/restriction.JPG

Nice! A bit of ceramic wool is certainly a quick and easy way to accomplish the task - wish I'd thought of that before I spent all that time sawing insulating firebrick into thin slices and painstakingly screwing the crumbly stuff together!

[DCish]

Feb 9, 2019 21:12:30 GMT -8 gadget said:

All this vortex talk reminds me of the Rangue-hilsch vortex tubes we use to use to test chocks on carburetors back in my early days as a mechanic. They plugged into shop air and put freezing cold air out one end and hot air out the other. No moving parts but it needed highly compressed shop air to work. Flow rate was very low. Temperature difference from each end was very high.

The cones where important in the design.

Fascinating gadget, Gadget! I continue to be impressed with all the things that can be accomplished with just shapes and flow.

What is the hypothetical benefit for a wood heater? If its just to trap heat for combustion could that not be easily done with an insulated bell type setup? How about trapping carbon for later burning? Really good mixing? I like the idea of a carbon trap/reactor.

The benefits I would say we are looking for are trapping heat so combustion can be as complete as possible, and introducing enough of the right kind of turbulence at the right time so that good enough mixing is accomplished. I haven't gotten to write this up yet, but... Over the weekend I took Vortex's standard 9" x 4.5" double vortex generator and added roughly 2.5" to each dimension. Normally, the 9 x 4.5" box is glowing red inside (1200 - 1500F) for a good portion of the burn. I was wondering if enlarging the box might allow for longer dwell at elevated temperatures as the hot gasses pass across the top and sides and swirl inward for longer before exiting the area. Turns out not to happen that way. A standard run produced more of a fire fountain than double vortex, the gasses having a much longer journey to reach the top of the box. Only small patches of the top and sides glowed at any point, no matter how hard I pushed it. Without a gas analyzer I can't say how efficiently it burned (Peter's DSR did better with a fire fountain than with a double vortex, after all), but I can say that the walls were certainly much cooler with the same amount of heat spread over a larger area.