
Thermodynamics and Propulsion

11.1 Overall Efficiency

$\displaystyle \textrm{overall efficiency}$	$\displaystyle =\frac{\textrm{what you get}}{\textrm{what you pay for}}=\frac{\textrm{propulsive power}}{\textrm{fuel power}}$
$\displaystyle \textrm{propulsive power}$	$\displaystyle = \textrm{thrust}\times\textrm{flight velocity} = T u_0$
$\displaystyle \textrm{fuel power}$	$\displaystyle = \textrm{fuel mass flow rate}\times\textrm{fuel energy per unit mass}=\dot{m}_f$

Thus

$\displaystyle \eta_{\textrm{overall}} = \frac{T u_0}{\dot{m}_f h}$

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