747400sp From United States of America, joined Aug 2003, 3301 posts, RR: 2 Posted (7 years 9 months 3 weeks 19 hours ago) and read 5146 times:
I was wondering about the size of the GE4/J5P and JTF-17 after burning engines. Since I been in the Navy I developed a fascination with after burning engines. Seeing that the GE4/J5P and JTF-17 could produce 60,000 lb + of trust with afterburners, it got me to thinking how big are these engines. The B-1 F-101 is 55 " in diameter and just produce 30,000 lb + of trust. So I just wanted to know, what is the diameter and length of these after burning monsters.
GDB From United Kingdom, joined May 2001, 12948 posts, RR: 79 Reply 1, posted (7 years 9 months 3 weeks 8 hours ago) and read 5104 times:
Not got the data for the GE4, but I know a man who probably has, Air Net member B2707SST.
Had it flown, it perhaps would have put the noise of 4 x Olympus 593's, reheated on take off, into perspective?
Av Week and every other source list that same 55" figure, but I suspect that's installation envelope, not fan tip diameter, which is the parameter you really need to work with for airflow & thrust comparison purposes. Fan tip diam. will of course be a little bit less than envelope, but I don't know how much.
"Eight Decades of Progress", the 'official' history of GE Aircraft Engines, doesn't list any specific dimensional data for the GE4. Judging from photos in the book, I'd guess the GE4 fan tip diameter is 60-65 inches. I'd be interested to know the actual value. I'll continue searching while we await Mr. B2707SST's response.
B2707SST From United States of America, joined Apr 2003, 1362 posts, RR: 60 Reply 3, posted (7 years 9 months 1 week 20 hours ago) and read 4951 times:
As GDB and F14D4ever mentioned, I do have some technical data on the GE4 and JTF17.
The GE4-J5P variant for the Boeing 2707 was a single-stage turbojet intended to generate 63,200 lbs. augmented thrust. Rotating machinery comprised nine compressor stages and two turbine stages. Engine diameter was 74.2 inches, length was 308 inches, and weight was around 10,500 lbs. each. Mass flow was 620 lb/sec. On test at rated takeoff thrust, the mass flow was found to be slightly higher and noise slightly lower than anticipated.
Late in the SST program, the 2707's weight had ballooned beyond the original 675,000-pound estimate, the aerodynamic efficiency of the fixed-wing -300 had degraded significantly compared to the swing-wing, and jet noise had become a crucial issue. To resolve these problems, the mass flow was to be increased to 720-815 lb/sec, with the latter more likely. The afterburner was to be deleted, which was also proposed on the improved Olympus for Concorde "B", and new noise suppressors were proposed. Thrust would have increased to well over 70,000 lbs. The increase in mass flow would have required 2 inches more diameter and would have increased total aircraft gross weight by 40,000-50,000 lbs. as the effect of the heavier engine cascaded through the airframe. The program was (mostly coincidentally) canceled about a month after these changes were proposed.
The JTF17A-21L proposed for the Lockheed L-2000 was a low-bypass turbofan with afterburning capability in the bypass duct only (a "duct-burning turbofan"). It was to generate 60,760 lbs. of augmented or 38,130 lbs. of non-augmented thrust at takeoff. Bypass ratio was 1.3:1. I know I have seen more detailed specs for the JTF17 but can't find them at the moment. As of late 1966, it was considerably shorter and "fatter" than the GE90 and was somewhat heavier and more expensive as well.
Normally, one would expect a turbofan to be quieter than a turbojet. Boeing's specifications included figures for both GE and PW power, and according them, the JTF17A created just as much sideline noise (117 PNdB) and was actually noisier than the GE4 during takeoff (95 PNdB vs. 104 PNdB) and landing (107 PNdB vs. 116 PNdB).
Given Concorde's FAA noise figures, it looks like the 2707-100 would have been significantly quieter on takeoff and approach. This is understandable because the swing-wing provided L/Ds more than three times greater than a double-delta at low speeds, so climb rate at a given thrust is greater and less power is needed for a given descent rate, respectively. With the fixed-wing 2707-300, though, all bets are off. Note that neither takeoff nor landing figures incorporate operational procedures like decelerating approaches. The extra thrust of the GE4s does come out clearly on the sideline measurement. For the 2707, the noise figures below do not include actual GE4 test data or new silencer designs that came later in the program.
B2707SST From United States of America, joined Apr 2003, 1362 posts, RR: 60 Reply 11, posted (6 years 10 months 1 week 6 days 12 hours ago) and read 4412 times:
Interesting to see this thread come back from the dead! Here is some additional JTF-17A data sent to me by a correspondant several years ago. I'm not sure where it comes from and can't completely vouch for accuracy, but I don't see any obvious mistakes either:
PRATT & WHITNEY JTF17A
Type: Two-shaft axial turbofan with duct heater.
Intake: Annular, titanium, no inlet guide vanes.
Compressor: Low pressure system consists of titanium case, two fan stages, titanium & Waspaloy blades & disks, bypass ratio 1.3:1, mass flow 687 lbs/sec.
High pressure system consists of titanium case, six compressor stages, titanium and Waspaloy blades & disks, compression ratio 13:1.
Combustor: Gas generator and duct heater combustors are advanced annular ram induction burner designs housed in Waspaloy cases. No diffusers - - velocity head of air provides a turbulent burning zone.
Turbine: High Pressure turbine is one stage, air cooled, with cobalt-nickel alloy disk and cobalt-nickel alloy blades, directionally solidified precision cast method, in Waspaloy case. Turbine Inlet Temperature is 2,200 degrees F, 2,300 degrees F for takeoff only.
Low Pressure turbine is two stages; otherwise same as high pressure turbine.
Exhaust: Reverser/Suppressor section with fixed convergent-divergent exhaust nozzle for primary gas stream, variable nozzle on duct exhaust, variable ejector, clamshell doors inside R/S section, aerodynamically actuated flaps at end of R/S section, tertiary air blow-in doors at front of R/S section, integrated advanced thrust reversal and noise suppression system.