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# Gas Powered Rotating Impellers?

## Gas Powered Rotating Impellers?

(OP)
New to the forum, please don't crucify me if this is a silly question. I am interested to know if it is possible to pump gas downward into a vertical cylindrical tube and transmit that gas horizontally at about the midpoint of the vertical piece in order to power multiple 360 degree rotating impellers

Does an apparatus like this already exist?

Approximate diameter of vertical piece would be 0.5"-1.5"
Approximate width of each impeller 2"-4"
Max PSI level of gas= 50 PSI

### RE: Gas Powered Rotating Impellers?

Like a rotating sprinkler head, except gas and liquid change places? Couldn't make much sense of the sketch.

### RE: Gas Powered Rotating Impellers?

(OP)
Edit/Update: Impellers are needed to mix liquid at a low rate, no more than 50 RPM's. Basically enough to create an initial mixture and maintain it (if that makes sense) do not need the impellers to have the effect on the liquid of something like a high shear impeller.

### RE: Gas Powered Rotating Impellers?

its when you started talking about liquid that I got lost. I assume when you say you want to power impellers means you want to generate mechanical energy from fluid power.

Typically if you accelerate/ decelerating the fluid in a turbo machinery, you are absorbing/generating mechanical power at the shaft, respectively.

So in your case you sould decelerate fluid to generate shaft power.

I dont see how this (centrifugal deceleration) can happen when the fluid flows from inlet radius toward outlet radius according to your sketch.

So my humble answer to your question is : I beleive this machine does not exist because it works contrary to the law of physics.

"If you want to acquire a knowledge or skill, read a book and practice the skill".

### RE: Gas Powered Rotating Impellers?

(OP)
@rotw, The bit about the liquid was what I want to accomplish with the motion of the impellers. Basically what I am wondering is if I can produce mechanical energy using gas from a vertical inlet to a horizontal outlet to power the motion of the impellers by pumping gas internally inside of the impellers to create the movement

### RE: Gas Powered Rotating Impellers?

already explained my opinion on the matter. you cant expand gas in a centrifugal wheel from inward radius to outward.
Furthemore where are you going to put the gas ? it is going to mix with the liquid is it desired or a (messy) side effect?

Why not letting the flow of the gas going axially downward through the tube while puting an axial expansion device inside the tube.
The tube will rotate and drive the mixer connected to it (what you previously called "impeller").

The axial expansion is sort of axial turbine.

"If you want to acquire a knowledge or skill, read a book and practice the skill".

### RE: Gas Powered Rotating Impellers?

(OP)
@rotw Thanks for your criticism, I genuinely appreciate it since I'm not well versed in the engineering world. As far as your axial device suggestion, are there devices currently utilizing this design that I could look up for reference? How would you recommend testing the axial device in an inexpensive way?

### RE: Gas Powered Rotating Impellers?

(OP)
@rotw Also, just realized I forgot an important piece, the objective here is to mix the liquid without the gas directly interacting with the liquid

### RE: Gas Powered Rotating Impellers?

the axial flow allows you to avoid the gas interacting with liquid I guess.

Well I dont know about a reference, the concept is just what came up to my mind.

As for the axial device itself, it needs a study - few things to look at:

- what gas conditions pressure, temperature (enthalpy so to say) do you have available upstream the turbine.
- how much torque / power is required to mix the liquid
- is the speed compatible (an axial turbine usually spins quite fast) while a mixer may need to rotate slowly, that worries me

Maybe a planetary gear...no that would be a bit too far...

"If you want to acquire a knowledge or skill, read a book and practice the skill".

### RE: Gas Powered Rotating Impellers?

If you can't mix the gas with the liquid, then what is the point of putting the gas down there? Get a pneumatic motor that sits above/outside the fluid and figure out the rest of the assembly without the added complication of having to seal things off.

http://www.mcmaster.com/#pneumatic-motors

### RE: Gas Powered Rotating Impellers?

There are some turbines called radial turbines which take inlet flow axially and exits radially. One example is Ljungström turbines. Refer the site:

However this may be too expensive and not sure this will meet with your requirements.

### RE: Gas Powered Rotating Impellers?

"Also, just realized I forgot an important piece, the objective here is to mix the liquid without the gas directly interacting with the liquid" That particular detail sealed the fate of the original design. Better get back to the drawing board.

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