Axisymetric Inlet Design for Combined-Cycle Engines Jesse R. Colville, Ryan P. Starkey, and Mark J. Lewis University of Maryland, College Park, Maryland

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Axisymetric Inlet Design for Combined-Cycle
EnginesJesse R. Colville, Ryan P. Starkey, and
Mark J. LewisUniversity of Maryland, College
Park, Maryland

• Presented by Andrew MacKrell
• AME 50531 Intermediate Thermodynamics
• University of Notre Dame
• April 30, 2008

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Abstract

• Examined a new strategy for designing inlets for
  Turbine-based combined-cycle (TBCC) engines
• Starting characteristics are examined compared
  with of the Kantrowitz limit
• Widened shoulder centerbody and variable cone
  with reextension designs have the ability to
  remain started into the Mach 6-7 range

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TBCC Engines

• Low speed Turbojets merged with high speed
  Ramjets and Scramjets
• Challenge Integration of the TBCC cycle modes
  into a single system
• Each requires unique flow properties to operate
  properly
• Inlet must provide efficient compression for all
  components across a wide Mach spectrum

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Inlet Performance

• Imposes a significant constraint on overall
  operation of engine
• Needs to
• diffuse required amount of air and maximize
  pressure recovery while minimizing shockwave
• Supply air with tolerable flow distortions
• Minimize amount of added external drag
• Minimize added mass
• Provide self-starting capability

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Study Model Assumptions

• SR-71 Blackbird engine inlet
• fastest manned air breathing aircraft
• Constant Ratio of Specific Heats
• Level, Steady Flight
• Incoming air is uniform
• One-D Isentropic Flow
• Air is perfect gas

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Calculations and Measurements

• Internal Area Ratio that produces sonic flow at
  the throat
• Measured Experimentally
• Self-start benchmark Kantrowitz Limit
• a
• a
• Isentropic Contraction Limit
• A

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Inlet Modifications

• Variable Cowl Leading Edge
• Variable Cone Centerbody
• Reextended Spike
• Widened Shoulder Centerbody
• Variable Cone With Reextension

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Results

• Variable Cowl Leading Edge and Variable Cone
  Centerbody modifications exhibited sub standard
  starting characteristics
• Variable Cone with Reextension and widened
  shoulder centerbody showed promise

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Conclusions

• Complex variable geometry is needed to design
  inlets for high speed aircrafts
• Numerical simulation was not entirely accurate
• Mechanical complexity associated with the complex
  variable geometry is the main obstacle that would
  need to be overcome to realize these design
  schemes