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Efficiency of jet engines

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Old 28th Dec 2002, 23:10
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Efficiency of jet engines

If around 27% of heat energy is converted into useful work in a piston engine, can anyone tell me how much heat energy is converted into useful work in a jet engine?
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Old 29th Dec 2002, 14:14
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The conventional wisdom is that good piston engines typical achieve about 30% thermal efficiency, and jet engines achieve about 20%. These are of course generalisations. But the (UK) tax man always gets the first 85% or so if its a car that you are driving!
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Old 30th Dec 2002, 20:51
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Steam (external combustion) engines = 20%
Piston (internal combustion) engines = 30%
Gas turbine engines = 30%
Electric motors = 95% !!

These figures are of course very approximate due to the range of variables involved.
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Old 30th Dec 2002, 22:06
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Thanks guys. And apparently the human body is 24%.
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