Richard White wrote:

F. Marc de Piolenc wrote:

Not data per se - just that all the design literature I have on
gas turbine design and gas turbine installations in aircraft
emphasizes the need to keep flow into the first compressor
stage subsonic. Inlets in supersonic military 'planes are designed
to "shock down" the flow to achieve this end.

Paul wrote:

I think we are getting things a little confused here. The fan
tips are what we are concerned about and the sudden drag
increase as they approach mach one.

F. Marc de Piolenc wrote:

I was referring to the FAN tips, ...

Richard jumps back in:

Yes, a diffuser duct keeps the horizontal speed of the air subsonic
as it flows into the fan tips.  But the tips themselves are whirling
about at supersonic speeds.  Perhaps this is the source of
confusion.  I agree with what Marc said above.  The two textbooks
I have read about turbofan design both say to keep the air flow into
the face of the fan subsonic.  This is not at all the same thing as
keeping the tip speeds subsonic.

This has been a fascinating discussion.  I am interested to see what
cool ideas and information come out of this as it applies to rotary
powered airplanes.

Happy Times Upon You,
Richard.

Me too. Perry is our man on the project. Any improvements will
come from him. Ducted fans certainly are attractive because
the rotary engine is so small in diameter.

Paul Lamar
 
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