A cyclone typically comprises a tangential entry to the large end of a cone, a small axial flow out of the small end, and a large flow axially out of a cylinder concentric with the cone. It removes particles by accelerated settling toward the cone surface as the flow's rotation rate increases and the radius decreases while the fluid is traveling down toward the cone tip.
Somewhere I found equations relating the proportions of a cyclone to flow rates and particle size, but I can't recall them right now. The point is, the math exists.
The flow exiting the apparatus through the cylinder is highly rotational. I have appended reverse cyclones in several configurations to the exit cylinder of a liquid cyclone, but they were not able to recover a substantial fraction of that rotational energy. I.e., from outside, a cyclone acts pretty much like a centrifugal pump in reverse, except you don't get any shaft power out.
I have since been exposed to swirl vanes in gas flows in tubes around 6" diameter and somewhat larger. I remain unimpressed by their efficacy. Even relatively deeply curled vanes (like a STOL aircraft wing with full flaps) really don't deflect the flow enough to call it 'rotational'. At best, each vane acts to redirect some of the gas passing near it in a direction that is mildly skewed to the tube axis. The flow impinges on the downstream tube wall at a low angle of incidence, and _that_ causes the overall flow to swirl, slowly.
I'm guesstimating that you'd need multiple rows of vanes, each nearly filling the cross section of the tube, in order to get enough rotational speed to affect accelerated settling.
There might be a way to make a uniflow cyclone as you wish. You might even find it.
Before you get real pumped up about the idea, I suggest you read up on erosion of fan blades. It should be covered fairly well in the literature for helicopters, where the air flow is more likely to carry abrasive dust.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
