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1
MAE 112 Propulsion
Homework Assignment #6
Due: February
27, 2009
1)
Suppose we had two parallel flows with equal mass flow rates, one at a stagnation
temperature of 1800
R and the other at 2400
R.
Each flow had a stagnation pressure of
fifteen atmospheres, a value of
= 1.3, and a value of c
p
= .30 Btu/1bm
R.
Calculate the
total thrust from nozzle expansion in each of the following two cases.
a)
The flows are mixed adiabatically at very low velocities and then expanded to
ambient pressure of 0.8 atmosphere in one nozzle.
b)
Each flow is expanded to the 0.8 atmosphere ambient pressure through a separate
nozzle.
2) Consider a turbofan engine flying at a Mach number of 0.85 with an ambient pressure
of one atmosphere and an ambient temperature of 480
R.
The intake has .98 polytropic
efficiency. The air is divided with a bypass ratio of 5 into a primary and a secondary (or
bypass) flow at the exit of the air intake.
The primary flow passes through a fan and
compressor combination with a pressure ratio of 28 and polytropic efficiency of .98 while
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 Spring '09
 Sirgianno

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