THEORY OF PROPULSION 5' Inlets

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THEORY OF PROPULSION 5. Inlets

• P. M. SFORZA
• University of Florida

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Inlet Requirements

• Duct air to the engine with low drag and total
  pressure loss
• Diffuse flow to high pressure and low Mach number
• Minimize flow distortion in flow to engine
• Handle range of mass flow
• Low weight, small size, and mechanically simple

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Inlets set up flow for the compressor
inlet compressor combustor turbine nozzle
20p0
2V0
V0
p0
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Subsonic inlets
0 1 2

M0lt1
compressor
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Subsonic inlet
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Captured streamtube for subsonic inlet
M00.5 M01
Inlet
M00
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Subsonic inlet with M0gt1
Streamlines dont know about shock wave so are
straight
Streamlines must bend away from axis, so A0ltA1
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Normal Shock equations

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2

normal shock wave
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Jump conditions across a normal shock (gconstant)
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Maximum mass flow in subsonic inlet at M0gt1
A0A1
Mlt1
M0gt1
1 2
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Subsonic inlets at M0gt1
MgtM0
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Normal shock inlet with different p2
A0/A11.02 A0/A10.91 A0/A10.81
M01.14
Note Mass flow error0.03
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Internal compression inlet
1
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Internal compression inlets for M0gt1
Shock expelled
Inlet started
Shock swallowed
Shock adjusted
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Critical areas across a shock
Recall that the maximum mass flow rate in a
streamtube is
Ms pt,0 Tt,0
My pt,y Tt,y
Shock wave pt,0gtpt,y Tt,0Tt,y gconstant Wconsta
nt
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Example of an internal compression inlet with Ms2
For M0lt1
But AminA0
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Internal Compression inlets
For MsgtM0gt1
For M0gtMs
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Comparison of inlets
Internal compression inlet
Normal shock inlet
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Internal compression inlets off design
pt,2/pt,00.0.83
pt,2/pt,00.72
pt,2/pt,00.39
pt,2/pt,00.33
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Internal compression inlet at MsgtM0gt1 and M0lt1
pt2/pt,00.93 (A0/A1)max0.90
pt2/pt,01 (A0/A1)max1.1
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Additive drag
pavg
p1
p0
A0
0 1
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Additive Drag (continued)
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Additive drag (concluded)
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isentropic compression
near isentropic compression Dpt(Dd)3
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External compression inlets (Ferri-Nucci inlets)
Three-shock inlet
Two-shock inlet
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Off-design operation and additive drag
Subcritical flow
Supercritical flow Schlieren flow
visualization at M02
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Operation at different M0
M01.49
M02.44
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Operation at different M0
M02.73 M03.01
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Oblique shock wave angle vs flow deflection
(g1.4)
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Mixed compression inlets

• Reduced cowl drag
• Increased gust sensitivity
• Increased unstart distortion

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Mach 3.5 inlet model schematic
RLcowl lip radius 24.86cm
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Mixed-Compression Inlet