Cyclonic rocket.

[satamax]

Hi everybody.

Well, i'm Max from france. In the southern alps, by the italian border. Living about 4900ft high. Cold snowy climate in the winter.

I needed to heat my workshop, and bumped on a website, on a small description of a rocket mass heater.

The smokeless part got me.

So i started gathering the parts, and made a prototype. Turned out way good imho.

So, it's a four incher, but with a twist. Since after discovering about thoses i read a bit. I understood that longer high temp burn was good, so, i thought why not make it cyclonic? A cyclone, in woodworking workshops, is a separator between air and fine dust and shavings. I've made one in the past, following Bill Pentz plans, which are online. And it keeps the air, or in this case, gasses, turning in a cyclonic motion inside, like, it's not static, but spends longer time in the second burn chamber which is the first gaz bottle.

I didn't want to bother with a cone, so i used a gaz bottle with a neutral vane to give a bit of that cyclone twist. Feed tube burn chamber is hydraulic tube, something like 5/16 thick. Four inch inside diameter. Gaz bottle, heat riser is comon aluminised stove pipe, with an outer jacket made of hvac galvanised tube, filled with vermiculite, and a barrell/radiator made out of a tall 35kg gaz botle. Well, now, onto the pics. Nough talk











Laurence fidling with it.

First atempt at plumbing it in.

Hot air thrown into the workshop. Didn't work much.

Latest way of plumbing it in, directly in the workshop.




Hope you like it. And also that someone will try the cyclonic effect, so someone else can tell if it's good or not.

Bye.

Max.

[Deleted]

Hi !

Insulating the burn chamber does not seem to be a good idea,
as you want the heat in the room.
To protect yourself from touching the hot surface you could put some tube around with a not to broad gap
in which the air can be sucked in and leave warmed.
you do not have enough surface to heat your workshop and forcing the smoke against gravity can make problems too.
There are flexible tubes for chimneys which can be bend do a spiral thus enhancing the surface a lot.
A bit expensice though.

[peterberg]

Hi Max, welcome to the board.
Trying to use a cyclone instead of a burn tunnel has been done before. Last summer I've been experimenting, very interesting. For a bit more info: donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=355

A well made cyclone rocket is capable of very low CO levels.

@karl,
Insulating the burn chamber is exactly the reason why a rocket is performing so well. Keeping the combustion temperature as high as possible is the very essence of this stove.

[satamax]

Yeeha! I'm not alone

Neutral vane.

billpentz.com/woodworking/cyclone/CycloneMods.cfm

But a coton shaker cyclone type would may be work better.

[pinhead]

The only thing I'd change is your transition from the secondary chamber to the exhaust; check out the Helpful Hint thread.

[satamax]

Thanks a lot Pinehead. Well, it's true. Intake of the feed tube is 105mm, and flue is 111mm. 139mm for the inside tube of the heat riser, 290 for the radiator and cyclone.

I should have made my exhaust elbow bigger. But i built with what i have. And now that it's plumbed in and works fine, it's staying that way. If ever i get a bigger workshop and flat above. I'll remember that.

[Deleted]

peterberg
The very essence of this stove is that the wood gas can not leave the path of the flame.
As it can not leave more of it will release its chemical energy and expand while broken down in smaller parts.
Trying to expand in a small profile it can only gain speed.
The higher speed will draw more air inside.
One mol of gas (0°C, 1013 mbar) will fill 22.4 liter.
Smaller parts -> more volume -> more speed -> more air intake -> more complete combustion -> smaller parts.

More heat kept inside the chamber will certainly help to break down the wood,
but not necessary lead to a hotter flame and better combustion.

[Deleted]

One could try to kill two birds with one stone by covering the chamber and a part of the chimney with a second tube.
Air will be sucked into the gap and heated up.
This hot air can be used to provide some preheated second air to the fire and for heating up the room.

[Deleted]

@ satamax

Turbulences will usually create a better mix of gases and air.
This could be managed by eccentric crossing of the tube parts without extending the diameter.
In a rocked stove burning chamber and chimney are not clearly separated as the flame will burn
in the chimney too. Extending the time in the "burning chamber" is not needed but extending the time in the path of the flame.
In the web one can find pictures of rocket stove flames extended to a meter ore more.
By allowing the gases to expand early in the gas bottle you are inevitably cooling down them and shorten the flame.
A cyclonic effect in the extended diameter may potentially even help some gas to escape the flame unburned.

But as you said you have worked with what you had and are quite satisfied with the result.

[satamax]

Nov 11, 2011 10:45:16 GMT -8 peterberg said:

Hi Max, welcome to the board.
Trying to use a cyclone instead of a burn tunnel has been done before. Last summer I've been experimenting, very interesting. For a bit more info: donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=355

A well made cyclone rocket is capable of very low CO levels.

@karl,
Insulating the burn chamber is exactly the reason why a rocket is performing so well. Keeping the combustion temperature as high as possible is the very essence of this stove.

Peter, i was wondering, did you, or anybody else try to use a cone shaped heat riser ? Lateral burn chamber with neutral vane, casted and insulated cone, tall heat riser above the cone and a barrel covering the heat riser. That would be proper cyclonic.

[Donkey]

I have tried a couple of different conic heat risers..
My results have been inconclusive thus far.

[woodburner]

Nov 12, 2011 2:15:06 GMT -8 @karl said:

peterberg
The very essence of this stove is that the wood gas can not leave the path of the flame.
As it can not leave more of it will release its chemical energy and expand while broken down in smaller parts.
Trying to expand in a small profile it can only gain speed.
The higher speed will draw more air inside.
One mol of gas (0°C, 1013 mbar) will fill 22.4 liter.
Smaller parts -> more volume -> more speed -> more air intake -> more complete combustion -> smaller parts.

More heat kept inside the chamber will certainly help to break down the wood,
but not necessary lead to a hotter flame and better combustion.

Can you explain in another way karl? I agree that trying to expand in a small profile the gas will gain speed, but i don't understand that it will draw more air inside than it would draw in if it was to expand in a larger profile. If it is expanding in a small profile, as well as increasing the speed towards the exhaust, it is increasing the pressure, and so reducing the speed at which air can get in the inlet.

Also if more heat is kept inside the chamber, the only thing the temperature can do is to rise.

[Deleted]

Posted by woodburner on Yesterday at 4:12pm

Can you explain in another way karl?

A part of the answer why a larger chamber is not so good can be found here.
picasaweb.google.com/Jonnygms/FinsInMudRocketStoves

I agree that trying to expand in a small profile the gas will gain speed, but i don't understand that it will draw more air inside than it would draw in if it was to expand in a larger profile.

A medium moving in tubes causes an under pressure depending on its speed.
Presure goes in any direction, thus the pressure towards the entrance is lowered too.
Aside of the under pressure there is an entrainment effect raising or falling with the speed.
With lowered pressure and surface the friction will be lower and with raised pressure and
surface there will be more friction.

If it is expanding in a small profile, as well as increasing the speed towards the exhaust, it is increasing the pressure, and so reducing the speed at which air can get in the inlet.

See above.
While the volumes moving in the system may vary with pressure and temperatures,
the mass moved has to be the same at any point of the system, if there is no condensation or other kind of fallout.

At the point the gas is entering the larger bottle to create the cyclonic effect the gas is still not burnt completely.
By giving it more room and cooling it down this way it becomes more likely that parts of it
will escape unburnt. The cyclonic effect will not compensate this.

Also if more heat is kept inside the chamber, the only thing the temperature can do is to rise.

Without the the larger bottle the exhaust could have been lowered.
With hot gas flows around the temperature difference is lowered and less insulation required.