Re: Beating Carnot Engines

From: spike66 (spike66@attbi.com)
Date: Fri Feb 28 2003 - 11:21:59 MST

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    Chuck Kuecker wrote:
    >
    > An afterburner, on a jet engine, does not "extract" energy from the
    > exhaust - it dumps a large amount of fuel into the exhaust, providing a
    > rocket-like thrust augmentation. Afterburners suck huge amounts of fuel,
    > rather inefficently, which is why they are used only when absolutely
    > necessary...

    The term "rather inefficiently" is an understatement.
    If one looks at the curve for additional thrust vs
    additional fuel use, it is enormously inefficient. It
    amazes me that it would work at all: the afterburner
    tosses unburned fuel into the exhaust stream.

    Perhaps what they really had in mind is if a plane is going
    into combat it needs to lighten its fuel load somehow.
    Burning it inefficiently is no worse than just throwing
    it overboard unburned I suppose. An F-4 jockey told
    me the afterburners could run for a little less than
    5 minutes full tanks to empty.

    spike



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