Re: Some Turbofan Questions

From: (JVRusso)
Organization: America Online, Inc. (1-800-827-6364)
Date:         03 Jul 96 01:23:55 
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Regarding thrust generated by turbofan engines, I don't have exact
figures, but for high byass engines (PW4000, GE90, etc) the majority of
the thrust comes from the fan. The main purpose of the core (high
compressor/high turbine) is to generate enough horsepower to turn the fan.
The lower the bypass ratio, the more excess thrust is available after hp
is taken out to turn the fan.

As far as I know, most, if not all, military turbofan engines (F100, F110,
F404, etc) have 2 or more fan stages. This is related to the above, since
the fan is pre-compressing the air that goes thru the core and will
eventually be used as propulsive force. Hope that helps.