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F-4E(S) & F-4X

LowObservable

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Thanks! Great enhancement to my animal-husbandry-graduate-level understanding of PCC.

I suspect the answer to the question "what happens if the water runs out at those speeds?" is "you really, really don't want to find out."
 

sferrin

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LowObservable said:
Thanks! Great enhancement to my animal-husbandry-graduate-level understanding of PCC.

I suspect the answer to the question "what happens if the water runs out at those speeds?" is "you really, really don't want to find out."

*BOOM!* ;)
 

mz

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Lots of claims but I really wonder if it has some not very much talked about side effects, especially on engine durability...
 

Phantom-Phlyer

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shockonlip said:
sferrin is correct.

I would also point out LO, that a simple little thing like
cooling the air going into the compressor has major impact
on the compression process.

If you look at a compressor performance chart. It has
Compressor Mass Flow Rate on the x-axis and Pressure Ratio
on the y-axis. Going across the chart, rising at about
a 45deg. angle is the compressor operating line. At some
point on that line (say half way up) you are operating at
100% RPM, you're normal operating point.

At that 100% RPM operating point, you start water injection
upstream of the compressor.

Due to the cooling effect mentioned by sferrin,
the operating temperature of the compressor is reduced.
This does some neat things to the compression process:
The corrected RPM of the engine goes up (corrected
RPM = N/sqrt(theta); where N = engine RPM and theta is
essentially the temp (which is reduced due to PCC). Since
the denominator is reduced, corrected RPM goes up, which
moves the compressor operating point to the right on the
x-axis, to a higher Compressor Mass Flow Rate.

And since the operating line is angled at 45 deg. upward,
and we now moved the operating point to the right, we also
go up the operating line to a higher y-axis value, or a
higher Pressure Ratio!!

So PCC cools the compressor air, actually due to water
evaporation, and raises the pressure ratio and mass flow
rate. So the turbine and nozzle (the backend), as sferrin
mentioned, is actually passing more mass flow and therefore
more thrust.

There is a danger of compressor stall if we cause to fast
a temperature reduction without enough additional mass flow,
because then the compressor operating line will angle up
and cross the compressor stall line (which runs above the
operating line).

But if the PCC temperature reduction and mass flow is
correct for this engine, then the operating line, as it rises
due to PCC, will parallel the stall line, and no stall will
happen.

There is also the possibility of additives to the water
tank to preclude freezing, like alcohol, which helps the water
also evaporate in the compressor more quickly.

The idea is that you want to employ PCC until the air at
the compressor discharge is saturated. So say your in a fast
airplane and Mach number is increasing (helped by PCC too).
So, to achieve this, as the air into the compressor becomes
hotter (due to inlet compression at higher Mach), you increase
the PCC augmentation. So the possible PCC augmented thrust ratio
goes up with higher Mach number.

To give an idea of possible thrust augmentation multipliers,
on a chart I have at home in one of my propulsion books,
it shows PCC thrust augmentation of 2.6X at Mach 2 with
injected water-air ratio of around .115 (NACA TN 2083 - 1950).

So this is cool stuff (pun intended!)

>Wouldn't it be cool to find someone very rich to build an F-4X,
>just for s***ts and giggles....
We think alike!!
I found this very technical report that may be one in the same as in your text book.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092063_1993092063.pdf
 

shockonlip

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I found this very technical report that may be one in the same as in your text book.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092063_1993092063.pdf
[/quote]

Thanks Phantom-Phlyer !!

Thanks for finding this report!

It IS one of the reports in the References section of my textbook section on water
injection. So my textbook quotes it as well as the other one I quoted earlier.

THANKS VERY MUCH, I am looking forward to reading it!

My textbook calls this NACA Report 1006, 1951, and indeed Report 1006 is the
title of your report at the beginning.

But figure 4 in your Report 1006 looks very close to the chart
actually in my textbook, except that my textbook has a curve with highest augmentation
ratio of 2.6 at Mach 2 (at sea level). It also has a higher altitude augmentation ratio
of 2.0 (at 35,000 ft.) at Mach 2, and water-air ratio of .084.

Your Report 1006 reference goes up to an augmentation ratio of 2.08 at Mach 1.5 at
sea level, with water-air ratio of 10.6 (.106?) and a higher altitude augmentation
ratio of 1.53 at Mach 1.5 at 35,332 ft with a water-air ratio of 6.8 (.068 ?).

There are other charts in your report that seem very similar to what is in my textbook
as well but quoted for the other reference. The full title of that other reference from
my textbook is: Lundin, B.T., "Theoretical Analysis of Various Thrust Augmentation
Cycles for Turbojet Engines," NACA TN 2083, 1950.
 

shockonlip

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LowObservable said:
Thanks! Great enhancement to my animal-husbandry-graduate-level understanding of PCC.

I suspect the answer to the question "what happens if the water runs out at those speeds?" is "you really, really don't want to find out."

>Thanks! Great enhancement to my animal-husbandry-graduate-level understanding of PCC.
OK, too much detail! It actually helps me understand it better myself to teach it to
someone, so sorry I targeted you!

>I suspect the answer to the question "what happens if the water runs out at those speeds?" is "you >really, really don't want to find out."
Agreed, but the guys designing it want to find out so the pilot doesn't have to!
There will be other transients one has to watch out for as well, like an inlet
unstart. It would actually be interesting to find out. If the altitude is high
and dynamic pressure lower than denser altitude, it may help.
 

sferrin

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Tommy Thomason's book talks about Vought's plans for PCC on their XF8U-3 to get it up to Mach 2.9 :eek:

(BTW, lots of interesting info in that book that I hadn't seen before. Definitely want to buy it if you've ever been interested in the XF8U-3.)
 

shockonlip

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sferrin said:
Tommy Thomason's book talks about Vought's plans for PCC on their XF8U-3 to get it up to Mach 2.9 :eek:

(BTW, lots of interesting info in that book that I hadn't seen before. Definitely want to buy it if you've ever been interested in the XF8U-3.)

Thanks for the heads-up!

Yes, I have Tommy's XF8U-3 book, and enjoy it a lot!
Including the short discussion of the what might have beens on J58 powered XF8U's!
Another hot rodding project for the future! The XF8U-4 !!
 

shockonlip

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fightingirish wrote, trying to determine the source of the photos F-4X 01, F-4X 02, and F-4X 03:
>Original picture source might be the book "McDonnell F-4 Phantom: Spirit in the Skies" by Jon Lake & >David Donald, Aerospace Publishing / Airtime Publishing; Enlarged 2nd edition (October 1, 2002)

Thanks fightingirish for your attempts at find out the sources for these photos.

I was able to procure a copy of "McDonnell F-4 Phantom: Spirit in the Skies" Updated and Expanded
Edition, 2002. Although photo F-4X 01 is there (pg 181) (and I might add due to the quality of the
photo in the book (not the online copies however) one can see the tip of the PCC capable intake or
maybe it is the conformal water tank - I vote for tip of the inlet) on the other side of the airplane.
And photo F-4X 02 is on pg 204, I do NOT see photo F-4X 03 in the 2002 edition. I would expect there
are some nice photos of the starboard side of 69-7576 as modified as a F-4X model in existence
somewhere. This is just a heads up so you don't buy the 2002 edition expecting to see find F-4X 03.
 

fightingirish

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RF-4X Recce Platform
The RF-4X was a General Dynamics proposal for an advanced derivative of the F-4E Phantom II. This effort began as a joint Israel-US Air Force design for a photoreconnaissance aircraft capable of Mach 3+ dash speeds at an altitude of 78,000 feet.

Artist concept by George Grant Posted: 12 June 2014

Source: http://www.codeonemagazine.com/gallery_slideshow.html?item_id=3406


Edit 1:
The David Star on the backboard wing has been airbrushed away.
See also OBB's post #26. That artist concept looks like it is also done by George Grant.

Edit 2:
Updated caption.
The RF-4X, also known as the RF-4ES, was a General Dynamics response to an Israeli government RFP calling for a high-speed, high-altitude photoreconnaissance platform based on the McDonnell Douglas F-4E Phantom II. Following RF-4X concept definition during 1972, a contract was issued in 1974 calling for the modification of three operational IAF F-4Es to the new configuration. Specifications called for a maximum cruising speed of 2.4 Mach at 78,000 feet while carrying a single General Dynamics-developed high-altitude aerial camera with a sixty-six inch focal length offering stepped, side-to-side image capture.

Artist concept by George Grant. Posted: 12 June 2014
 

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shablul7

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taxiing out of it's shelter
 

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sferrin

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It doesn't look like this has been posted yet.

https://www.nas.nasa.gov/assets/pdf/papers/Mehta_U_February2015.pdf

Water injection pre-compressor cooling assist space access
 

Archibald

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sferrin said:
It doesn't look like this has been posted yet.

https://www.nas.nasa.gov/assets/pdf/papers/Mehta_U_February2015.pdf

Water injection pre-compressor cooling assist space access

Very interesting study. Could make for a nice cubesat launcher. Fast reponse, partially reusable.
 

sferrin

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Archibald said:
sferrin said:
It doesn't look like this has been posted yet.

https://www.nas.nasa.gov/assets/pdf/papers/Mehta_U_February2015.pdf

Water injection pre-compressor cooling assist space access

Very interesting study. Could make for a nice cubesat launcher. Fast reponse, partially reusable.

RASCAL seemed to be a purpose-built design using this technology for doing just that. Don't know why they didn't do it as the technology is old. (Skyburner used it as did the Mig-25 when the USSR went after the time-to-altitude records.
 

Archibald

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Because for the last 60 years, RLV programs in the United States have thrieved, then died, then started again, hundreds of time, with similar ideas forgotten, then discovered again, then forgotten. Rince, repeat. MIPCC is indeed quite an interesting technology.
 

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