Looks like the engine tops out at 7500 or so RPM which must be near the
non military throttle stop. From there the RPM's drop back down to about
7000 RPM during afterburner. The throttle stop is at about 1/3 total
throttle travel the rest is all afterburner.
So I'm seeing it like this: The engine can get the plane up to Mach 1.5
or so at top speed 66% of the thrust is ramjet. (if the throttle is
linear)
To be completely sure I'd need to see the BSFC for the engine.
7000 RPM at Mach 2.5 is certainly not off.
That got very interesting guys. Thanks
All turbines I know of find some use for bleed air and many have IGV's
some have VSV's as well.
I guess I can't exaggerate the features of the SR 71 as much as I used
to anymore. :)
Monroe
-------- Original Message --------
Subject: [AR] Re: What OSHA?
From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
Date: Thu, January 17, 2019 1:58 am
To: arocket@xxxxxxxxxxxxx
On Wed, Jan 16, 2019 at 09:19:00PM -0700, Monroe L. King Jr. wrote:
Yes, I believe this shows that above Mach 2.5 you have almost no flow
from the engine. You still have some at 1.5. Is that not correct?
One might think that from that particular diagram, but it's not
actually correct. As the manual puts it,
"The engine has a single-rotor, nine-stage, 8.8:1 pressure
ratio compressor utilizing a compressor bleed bypass at high
Mach. When opened, bypass valves bleed air from the fourth
stage of the compressor, and six ducts route it around the
rear stages of the compressor, the combustion section, and the
turbine. [...] The transition normally occurs in [...] a
Mach range of 1.8 to 2.0."
https://www.sr-71.org/blackbird/manual/1/1-4.php
Engine RPM is graphed here:
https://www.sr-71.org/blackbird/manual/1/1-20.php
(I'm not quite sure what all the lines in the graph represent, but
none of them get anywhere near zero.)
