Blackbird From , joined Dec 1969, posts, RR: Posted (6 years 5 months 3 weeks 3 days 14 hours ago) and read 6188 times:
I remember reading something about the F100 having these variable inlet-guide vanes (in addition to the regular variable-guide vanes in between the compressor stages) which are designed to lower the pressure-ratio at high-speed.
Is this true?
BTW: If so, and assuming it's not classified, does it work incrementally adjusting as the speed goes up, or all at once, when a certain mach-number or engine/compressor temp is reached?
DeltaGuy From , joined Dec 1969, posts, RR:
Reply 3, posted (6 years 5 months 2 weeks 4 days 13 hours ago) and read 5917 times:
No EEDF, it's not classified, not at all. It's a damn near 40 yr old engine.
They're first stage vanes, the very first stage of the engine is stators, and that's where they exist. They incrementally move more open as N1 and N2 come up, and are full open at mil power, I can't remember the exact full open point. They're scheduled by the DEEC (F-100-220/229)(On the F-100-100 that would be the EEC), and in case of DEEC failure and reversion to secondary mode, then they'll slam full closed..."better slow than blow" was what they said.
Blackbird From , joined Dec 1969, posts, RR:
Reply 7, posted (6 years 5 months 2 weeks 3 days 3 hours ago) and read 5830 times:
I thought it used a variable inlet-guide vane system kind of like the J-58 (I'm not just talking about the J-58's that powered the Blackbird, but all J-58's to my knowledge, even the early designs pre-Blackbird era). Past a certain compressor inlet temp, the guide-vane would adjust position lowering the alpha of the airflow to the compressor effectively lowering the pressure ratio of the engine. The idea was that it would also lower the turbine-inlet temperature and at a high-enough speed you'd derive enough off ram-compression anyway.
Let's hope I don't get a heart-attack or something