2007 JetMixing - Enhanced Jet Exhaust Mixing To Reduce Jet Aircraft Engine Noise Roy Myose Klaus Hoffmann Aerospace Engineering Department Wichita

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Enhanced Jet Exhaust Mixing To Reduce Jet Aircraft Engine Noise Roy Myose & Klaus Hoffmann Aerospace Engineering Department Wichita State University Skip Byrnes FAA Task Manager
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 2 Overview of Jet Engine Noise Issue Noise regulations becoming increasingly more stringent During take-off, most of the noise comes from high speed jet flow (shown in red) 60 70 80 90 100 110 Turbine Airframe Combustion Core Fan Inlet Core Exhaust Fan Exhaust Total Maximum perceived noise levels, dB Source: NASA Fact Sheet 1999-07-003-GRC
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 3 Motivator: Limit to Reducing Jet Flow Speed Reduced noise by slowing down jet exhaust flow But, there are limitations to jet flow speed reductions Source: Aircraft Noise by Smith (1989) Afterburning Turbojet Turbojet Low Bypass Turbofan High Bypass Turbofan 0 10 20 30 40 50 0 1000 2000 3000 4000 Jet Exhaust Velocity, ft/sec Difference in Noise Level, dB
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 4 Overall Background & Objective Overall background: Jet exhaust flow noise can be reduced by increasing the mixing between the jet and its surroundings Objective: Investigate different ways of increasing the mixing so that the jet exhaust flow noise can be reduced Source: Aircraft Engines & Gas Turbines by Kerrebrock (1992)
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 5 Technical Approach Literature survey Review fundamentals about jet noise production Seek out different jet noise suppression techniques Computational fluid dynamics (CFD) simulation Compare baseline CFD case with literature Perform CFD simulations of some promising noise suppression techniques Flow visualization experiments in tandem
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 6 Background: Downstream Development of Jet Velocity Profiles Constant center-line velocity in core region Reduced center-line velocity past core region Shock waves form inside core for high speed (supersonic) jets Shear layer where mixing Source: Viscous Fluid Flow by White (1974)
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 7 Jet Noise Suppression Methods Multi-tube suppressor Increased mixing due to multiple regions of shear Ejector Increased mixing by entraining slow moving air from surrounding Tabs Forced lobe mixer Chevrons Non-circular nozzle cross-sectional shapes
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June 2007 FAA CGAR Enhanced Jet Exhaust Mixing - Wichita State University 8 Tab Method Tabs placed in the flow act as "delta wing" type streamwise vortex generators which increases the mixing Disadvantage: tabs placed in hot flow stream makes them susceptible to thermal corrosion Source: ″Jet Mixing Enhancement Using Fluid Tabs" by Behrouzi & McGuirk (2004)
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This note was uploaded on 12/24/2009 for the course AEROSPACE engine taught by Professor Prof during the Spring '09 term at École Normale Supérieure.

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2007 JetMixing - Enhanced Jet Exhaust Mixing To Reduce Jet Aircraft Engine Noise Roy Myose Klaus Hoffmann Aerospace Engineering Department Wichita

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