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
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.
|Takeoff||119.5 PNdB||104 PNdB|
|Sideline||112 PNdB||117 PNdB|
|Approach||117 PNdB||107 PNdB|
[Edited 2006-03-04 23:16:21]
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