Learning About Air Coupling in Shafts - Diagrams Welcome!

[Shawnzyoo]

I am trying to learn more about air coupling.
That is the coupling between 2 shafts
I am having a hard time finding any information on the subject matter
does anyone know how these systems work and have any diagrams?
thanks

 

[FredGarvin]

Maybe it's because I haven't had my coffee yet this morning, but I can't say I have ever seen or heard of an air coupling for shafts. Can you point me to an existing application?

 

[Astronuc]

Does this have anything to do with concentric counter-rotating shafts?

 

[mezarashi]

Something like how when you blow one fan into another fan, the second fan's rotors start moving as well? It seems like a very weak sort of coupling... maybe better in more viscous fluids or the other way around?

 

[Shawnzyoo]

i was reading about this coupling with turbine engines from Pratt & Whitney.
i can't for the life of me find the link right now

but i think mezarashi has described it

 

[Danger]

So it's like a hydrostatic drive without the hydro? Sounds pretty inefficient.

 

[Astronuc]

Certainly, if one takes an axial flow from one fan and impose it on another fan, the second fan's blade will experience energy/momentum from the flow and start to rotate. That would be expected.

In conventional turbo-compressors and turbines, one normally has a set of stationary blades (stator) and rotating set of blades (rotor). For a very simple turbine or compressor with two stages, one could have counter-rotating blade sets. One can get comparable energy transfer but at reduced rotational speed.

As for hydraulic coupling - automatic transmissions use just that.

In the case of PW, how are the turbine engines suppose to be coupled?

 

[FredGarvin]

Engine spools do, at times, counter rotate to the other. The rotational directions are set up via gas path angles in the rotors themselves. I have not really heard of this as a coupling. The usual mechanical coupling is a curvic coupling. I'll do some seariching around now that you gave a hint to it's application. It would be nice to see the link you are referring to.