TheNiftyReptile t1_irnxpkm wrote
This is half true. At low altitudes with higher air density most of the thrust does come from the turbofan bypass, but as altitude increases and air density decreases, it is actually the jet engine core that contributes to most of the thrust.
InevitableRip8968 t1_irothk8 wrote
This is very wrong. Even at altitude the fan is what’s creating most of the thrust. The ratio of thrust between the core and high bypass stays the same at all altitudes. The overall performance decreases at altitude due to the air thinning out.
mrkmg t1_iroxar6 wrote
Well... The ratio does shift slightly, but not enough for the jet thrust overtake the fan.
But really I wanted to add:
Performance =/= efficiency. If you take the entire system (the thrust, fuel consumption, drag, etc) there is an ideal altitude that's really high up where the whole aircraft is most fuel efficient.
This stuff is so complicated that they use entire farms of servers to calculate expected performance and efficiency of aircraft designs.
InevitableRip8968 t1_irp38q4 wrote
Can you show me proof? Bypass ratio always stays the same. This is taking in to factor if you ignore bypass ducts that newer engines use.
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