Question

PROBLEM: Consider a jet plane in steady straight-and-level flight through still air at a speed U. Determine omgued, the fuel mass flow rate of one engine assuming the air density pe, engine intake area A, engine exhaust nozzle area, velocity and density A, U, and Pe, respectively are given. Both U, and Ue are speeds given with respect to a stationary observer on the ground as shown in the figure. Arope A.PL

Answer 1

Conserving the mass flowing into the engine and outside the engine we have

The mass flow rate flowing through the inlet is (dot representation is derivative w.r.t time)

m; = PiAU

The mass flow rate flowing through the exit is

  

me = Pe A(U+Up)

as the Ue is w.r.t stationary observer on earth the exit velocity w.r.t engine will be Ue + Up

Conserving mass we get

me = mg + mi

Thus

mg = Pe Ac(U+Up) - Pit;Up

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