mzaharis
Well-known member
- Joined
- Sep 27, 2004
- Posts
- 541
2 things:
1. I used to work on the J58 used on the SR-71 as a manufacturing engineer at P&W. It DID have a bypass of sorts, in the form of 6 gigantic tubes from the compressor to the afterburner, bypassing the combustion chamber and turbines. Not TRUE bypass of the type one would see in a turbofan, but some air did go from the compressor straight to the afterburner. The bypass amount could be changed based on engine operating needs. This is independent of the moving cone mentioned earlier that manages inlet shocks and keeps the oblique shock from the cone properly placed at the lip of the inlet.
http://aerostories2.free.fr/acrobat/technique/J58/J58A_genesis_eng.pdf
2. The GE F-120 turbofan, their contender for the Advanced Tactical Fighter (now known as the F-22 Raptor), had a variable bypass, their solution to efficiently adjust the engine between the needs of lower-speed flight and supercruise (Mach 1+ flight without afterburner). They never released drawings of the bypass valves, afaik. I was working on its competitor, the Pratt and Whitney F-119, which was selected, presumably due to its simpler, easier to maintain design (although, like any other military contract selection, the reasons are sometimes murky).
1. I used to work on the J58 used on the SR-71 as a manufacturing engineer at P&W. It DID have a bypass of sorts, in the form of 6 gigantic tubes from the compressor to the afterburner, bypassing the combustion chamber and turbines. Not TRUE bypass of the type one would see in a turbofan, but some air did go from the compressor straight to the afterburner. The bypass amount could be changed based on engine operating needs. This is independent of the moving cone mentioned earlier that manages inlet shocks and keeps the oblique shock from the cone properly placed at the lip of the inlet.
http://aerostories2.free.fr/acrobat/technique/J58/J58A_genesis_eng.pdf
2. The GE F-120 turbofan, their contender for the Advanced Tactical Fighter (now known as the F-22 Raptor), had a variable bypass, their solution to efficiently adjust the engine between the needs of lower-speed flight and supercruise (Mach 1+ flight without afterburner). They never released drawings of the bypass valves, afaik. I was working on its competitor, the Pratt and Whitney F-119, which was selected, presumably due to its simpler, easier to maintain design (although, like any other military contract selection, the reasons are sometimes murky).
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