1
Due:
January 29, 2010
MAE 112 Winter 2010
Homework Assignment #3
1. Consider a jet engine flying at a Mach number of 1.45.
A normal shock sits at the
entrance of the divergent diffuser.
The diffuser entrance crosssectional area is 2.75 ft
2
.
The ambient conditions are 490
R for temperature and 0.9 atmosphere for pressure.
(a) What is the stagnation pressure immediately behind the shock?
What is the Mach
number immediately behind the shock?
What is the mass flow through the diffuser?
(b) What is the minimum crosssectional area required at the other end of the diffuser in
order to insure that the Mach number of the flow entering the compressor does not
exceed 0.11?
2. Consider a KantrowitzDonaldson diffuser designed for a flight Mach number of 1.7.
The entrance area equals 2.2 ft
2
and the ambient air temperature and pressure are 520
R
and 0.8 atmosphere.
The flow is isentropic everywhere except across the normal
shockwave.
Determine:
(a) the minimum crosssectional area of the throat such that a normal shock may be
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 Winter '09
 LaRue
 Fluid Dynamics, Shockwave, Mach number, 0.4 square meter, 0.8 atmosphere, 0.9 atmosphere, 0.85 atmosphere

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