WP Marsh wrote:

Gentlemen,

I'm wondering if the PW J-58 (powering the SR-71) would have been
able to achieve 32k+ lbs of thrust each with NACA inlets.  I think
Kelly Johnson and his boys at the Skunk Works had the right idea:
Mach 3+ RAM AIR.  As I recall, Ben Rich spent a good deal of time
optimising the movable inlet cone to gain maximum inlet ram air
advantage.

IMHO, a NACA inlet is a passive, scavanging inlet, suitable for
cockpit cooling.  If you want HP, go RAM.

For a simple illustration,  fly straight and level at full smash,
then pull your carb heat.  Notice an RPM drop?  You've just gone
from ram air induction to passive (NACA-style) induction.

As for the images of the NACA induction for the Boeing APU, wasn't
there some kind of diverter in that setup that attempted to redirect
ain into the NACA scoop.  That looked like a pretty blatant
admission that Boeing was willing to sacrifice a bit of drag in
order to emulate the performance of the more effective ( but less
sexy) conventional scoop.

wp marsh

Correct me if I'm wrong but didn't Mr. Johnson design the movable inlet to
allow the incoming air for the engines to enter the engines at a sub sonic
speed [Does this in some way contribute to Ram effect?] to stop all kinds of
trouble in the engine.  They called it some sort of stall [can't remeber
right now] but I do remember pilots talking about how it was like smashing
up a car every time it did it. And some times it would do it several times a
minute.. and really slam them around. This was all before they got the
design perfected and was a non-issure later when it was all resolved. I'll
have to go back and re-read my 'Skunk Works' ...  He tells the whole story
in there...

Jarrett Johnson

 
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