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Old 09-28-2019, 12:49 PM   #394 (permalink)
Bicycle Bob
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Join Date: May 2008
Location: N. Saskatchewan, CA
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Appliance White - '93 Geo Metro 4-Dr. Auto
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Quote:
Originally Posted by litesong View Post
I was talking about airplane jet engines. Eventually high-bypass turbo-fans boosted jet engine efficiency without excess temperatures & nitrogen oxide pollution production.
Jet engines did benefit from better alloys and now ceramics, but the main benefit of the turbo fan is that it is more efficient at propulsion than a pure jet, because it grabs more air and thus stays out of the nasty end of the Froude calculations. It is better to push on stuff that is not already moving backwards instead of pushing harder, because you have to "shift to a higher gear" to do it, and that costs some of your push, just as a higher gear gives less torque at the axle.
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