Ram air

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