Hypersonic Inlet Fundamentals

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Hypersonic Inlet Fundamentals

• David M. Van Wie
• September 2007

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Outline

• Purpose of an Inlet
• Contrasting Ramjet and Scramjet Inlets
• Classes of High-Speed Inlets
• Background
• Inlet Performance Parameters
• Isolator Performance
• Inlet Operability
• Fundamental Phenomena
• Measurement Techniques
• Advanced Concepts
• Summary

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1. Purpose of an Inlet
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2. Contrasting Ramjet and Scramjet Inlets
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3. Classes of Hypersonic Inlets

• External Compression
• Internal Compression
• Mixed Compression
• 3D Sidewall Compression
• Streamline Traced
• Fixed versus Variable Geometry
• Combined Cycle Engines

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3. Hypersonic Inlets External Compression
Kholod flight test vehicle Axisymmetric hydrogen
-fueled scramjet engine.
External compression inlet suffer from high
external cowl drag.
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3. Hypersonic Inlet Internal Compression
Mach 8.3 Busemann Inlet Test
Busemann Inlet
Internal compression inlets generally will not
self-start.
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3. Hypersonic Inlet Mixed Compression
M0
Mixed external-internal compression inlets
balance needs for efficient compression, inlet
starting, and low external drag.
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3. Hypersonic Inlet Fixed versus Variable
Geometry
Variable Geometry
Fixed Geometry
M0
M0

• Simple, lightweight design
• Inlet must be designed to self-start
• Operable over limited Mach number, ? range

• Performance tailorable over operating range
• Variable geometry can be used to start the inlet
• Additional mass of actuators and seal complexity

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3. Hypersonic Inlet Streamline Traced
Busemann Inlet
Waverider Vehicles
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3. Hypersonic Inlet Combined Cycle Inlet

• Combined cycle engines are being explored for
  operation over large Mach number ranges
• Integration of two inlets into a single flowpath
  presents both operability and performance
  challenges

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4. Background Force Accounting
Freestream-to- Freestream
Additive Drag must be included when using the
freestream-to- freestream accounting System.
Cowl-Lip-to- Freestream
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4. Background Averaging Techniques
Stream Thrust Averaging
Massflow
Axial Momentum
Normal Momentum
Energy
State
5 Equation ---- 5 Unknowns
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4. Background Mass Flow Function
The mass flow function is a convenient quantity
used in the calculation of 1D flows. Note that
for a given gas, the mass flow function depends
only on Mach number.
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5. Inlet Performance Parameters

• Contraction Ratio
• Compression Ratio
• Air Capture Ratio
• Heat Loss
• Inlet Efficiency
• Inlet Drag

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5. Inlet Performance Contraction Ratio
Contraction Ratio
(Geometric)
(Effective)
(internal)
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5. Inlet Performance Air Capture Ratio
Air Capture Ratio
Oversped
Undersped
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5. Inlet Performance Heat Loss
Total Heat Loss
Fractional Heat Loss
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5. Inlet Performance Inlet Drag
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5. Inlet Performance - Efficiency
Total Pressure Recovery
Kinetic Energy Efficiency
Adiabatic Kinetic Energy Efficiency
Process Efficiency
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5. Inlet Performance - Efficiency
Ref. Van Wie, D. M., Scramjet Inlets, in
Scramjet Propulsion, AIAA Progress in
Astronautics and Aeronautics, Vol. 189, 2000.
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5. Inlet Performance - Efficiency
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6. Isolator Operation
Increasing isolator capability led
to Significantly increasing end thrust at Mach 5
test conditions.
Scramjet engine installed in JHU/APL freejet
engine test cell
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6. Isolator Operation
Ref. Waltrup, P. and Billig, F. S.
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6. Isolators Pseudoshock vs. Separation Shock
Operation
Pseudoshock Operation
Isolator bifurcation demonstrated by Penzin et.
al.

• Flow has 2-layer characteristic
• Flow contraction by separation lt2 of duct
• Influence of disturbances minimal
• Influence of boundary layer thickness small
• RMS Pt pressure fluctuations about 20

Separation Shock Operation

• Non-symmetric flow with 3D separations
• Flow contraction by separation about 15 of duct
• Operation very sensitive to flow disturbances
• RMS Pt pressure fluctuations about 150

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7. Inlet Operability

• Inlet Starting
• Maximum Contraction Ratio
• Shock-Wave/Boundary-Layer Interaction
• Maximum Back-Pressure

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7. Operability Inlet Starting
For any given Mach number, a range of internal
contraction ratio exists where two stable flow
situations can exist.

• Supersonic flow throughout internal convergence
• Steady flow conditions
• Throat condition does not impact air capture

• Boundary layer separation upstream of cowl lip
• Choked flow at inlet throat
• Large peak pressure at cowl lip
• Large unsteady pressure component

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7. Operability Inlet Starting
An estimate of the allowable internal contraction
ratio is obtained assuming A normal shock at the
cowl lip and sonic flow at the throat. The
resulting area ratio is known as the Kantrowitz
limit.
Ref. Kantrowitz, A. and Donaldson, C.,
Preliminary Investigation of Supersonic
Diffusers, NACA WRL-713, 1945.
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7. Operability Maximum Contraction Ratio
CRmax occurs at Mth-min
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7. Operability Maximum Contraction Ratio
Distortion Index
Minimum throat Mach number is a strong function
of flow distortion.
Ref. Cnossen, J.W. and OBrien, Investigation of
the Diffusion Characteristics of Supersonic
Streams Composed Mainly of Boundary Layers, J.
Aircraft, Vol. 2, No. 6, 1965.
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7. Operability Maximum Contraction Ratio
Approximate maximum contraction ratio
Ref. Van Wie, D. M., Scramjet Inlets, in
Scramjet Propulsion, AIAA Progress in
Astronautics and Aeronautics, Vol. 189, 2000.
32
7. Operability Shock-Wave/Boundary-Layer
Interaction
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7. Operability Shock-Wave/Boundary-Layer
Interaction
Ref Delery, J.M., Shock-Wave/Turbulent Boundary
Layer Interaction and Its Control, Progress in
Aerospace Sciences, Vol. 22, , 1985.
Ref. Stollery, J.L., Some Aspects of
Shock-Wave/Boundary Layer Interaction Relevant to
Intake Flow, Hypersonic Combined Cycle
Propulsion, AGARD-CP-479, June 1990.
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7. Operability Shock-Wave/Boundary-Layer
Interaction
M lt 4.5
M gt 4.5
Ref. Korkegi, R. H., Comparison of
Shock-Induced Two- and Three-Dimensional
Incipient Turbulent Separation, AIAA Journal,
Vol. 13, No. 4, 1975.
Ref. Law, C.H., Supersonic Turbulent
Boundary-Layer Separation, AIAA Journal, Vol. 12,
No. 6, 1974.
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7. Operability Shock-Wave/Boundary-Layer
Interaction
Ref. Frew, D., Galssi, L., Stava, D. and Azevedo,
D, A Study of the Incipient Separation Limits
for Shock-Induced Boundary Layer Separation for
Mach 6 High Reynolds Number Flows, AIAA 93-2481,
June 1993.
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7. Operability Maximum Pressure Ratio
A variable
Pt-pl
M0
Tt-pl
PCI combustor inlet pressure
Subcritical spillage
Pmax
Note Most high-performance mixed- compression
inlets exhibit little subcritical spillage.
Combustor Entrance Pressure, PCI
Last stable point
(A0/Ai)critical
Air Capture Ratio, A0/Ai
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8. Fundamental Phenomena

• Boundary-Layer Transition
• Leading Edge Effects
• Shock-Shock Interaction
• High-Temperature Gas Dynamics Effects

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8. Fundamental Phenomena Boundary Layer
Transition
Ref. Elais, T. I. And Eisworth, E.A., Stability
Studies of Planar Transition in Supersonic
Flows, AIAA-90-5233, Oct. 1990.
Ref. Ault, D.A. and Van Wie, D.M., Comparison of
Experimental Results and Computational Analysis
for the External Flowfield of a Scramjet Inlet at
Mach 10, J. Prop. Power, Vol. 10, No. 4, 1994.
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8. Fundamental Phenomena Leading Edge Effects
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8. Fundamental Phenomena Leading Edge Effects

• Tested at Calspan 48-in shock tunnel
• Mach 10 conditions

Rn 0.005 in
Schlieren Photographs
Rn 0.100 in
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8. Fundamental Phenomena Leading Edge Effects
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8. Fundamental Phenomena Shock-Shock Interaction
Ref. Wieting, A.R. and Holden, M.S.,
Experimental Study of the Shock Wave
Interference Heating on a Cylindrical Leading
Edge, AIAA Journal, Vol. 27, No. 11, 1989.
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8. Fundamental Phenomena Shock-Shock Interaction
Internal Strut
Strut damage due to shock-shock interaction.
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8. Fundamental Phenomena High-Temperature
Gasdynamic Effects
M0
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8. Fundamental Phenomena High-Temperature
Gasdynamic Effects

• Simple 1-shock conical inlet
• Flow conditions at Mach 20
• Impact of gas model readily apparent

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9. Measurement Techniques

• Air Capture Ratio
• Heat Loss
• Inlet Drag
• Inlet Efficiency

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9. Measurement Techniques Air Capture Ratio
Mass Flow Meter
Mass Flow
is a calibrated function of Re In the exhaust
nozzle of the Mass flow meter
Air Capture
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9. Measurement Techniques Inlet Efficiency
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10. Advanced Concepts

• MHD Flow Control
• Virtual Cowl

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10. Advanced Concepts MHD Flow Control
Experimental Demonstration
Inlet Flows with Mach 4 Inflow
Increasing Stuart Parameter
Ref. Effect of Magnetohydrodynamics
Interaction in Various Parts of Diffuser on Inlet
Shocks Experiment, S. V. Bobashev, A. V.
Erofeev, T. A. Lapushkina, S. A. Poniaev, R. V.
Vasileva, D. M. Van Wie, J. Propulsion and
Power, Vol. 21, No. 5, Sept-Oct. 2005
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10. Advanced Concepts Virtual Cowl

• Beamed energy deposited outside cowl to deflect
  flow into engine
• Energy obtained from either in-line or auxiliary
  MHD generator

Ref. MHD Power Generation in Scramjet Engines
in Conjunction with Inlet Control, M. N.
Shneider, S. O. Macheret, R. B.Miles, and D. M.
Van Wie, AIAA-2004-1197, Jan. 2004.
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11. Summary