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On Jun 3, 11:18 am, wrote:
On Jun 3, 10:18 am, "Ken S. Tucker" wrote: I wonder if ram scoops were ever installed near the prop tips. Probably too expensive for GA, but a WW2 A/C with tips spinning at what(?) 500-600 mph would give a nice pressure boost. I've read dual phase superchargers were used in recon A/C to get the speed and altitude. Airspeed off the tips is the same as the speed off the inner blade areas, due to the pitch washout across the blade span, so there'd be no advantage to having scoops behind the tips. The propeller's blades are flying at an AOA of between 2 and 4 degrees in cruise flight, anywhere between the tips and hub, because of that pitch variation. See Figure 6-4 of this page:http://www.allstar.fiu.edu/aero/flight63.htm Dan Dan it was a trick question I asked you. It's the basic aerodynamic physics of the standard centifugal supercharger compressor operating principle. I tossed you a zinger, cuz you claimed to be a teacher in a college and I couldn't resist :-), don't worry about it, hardly anyone get's that one correct, and I hope you get a ha-ha-ah from it. I mentioned, "dual phase superchargers" as a hint. Here's the answer: the ram-air pressure acquired at the prop tips is equal to the loss of pressure against the centrifugal force pushing air - via ducting - into the prop center that one obtains at the prop tips. Now you know the rest of the story. Regards Ken |
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