Document
National Aeronautics and Space Administration
Perceived Noise Analysis for Offset Jets
Applied to Commercial Supersonic Aircraft
Dennis L. Huff
Brenda S. Henderson
Jeffrey J. Berton
Jonathan A. Seidel
NASA Glenn Research Center
Cleveland, Ohio 44135
AIAA Aerospace Sciences Meeting, SciTech 2016
January 7, 2016
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Research Goals for Supersonic Aircraft
N+1 N+2 N+3 supersonic business small supersonic efficient multi - Mach class aircraft airliner aircraft (2015) (2020) (beyond 2030) Environmental goals Sonic boom 65 to 70 PLdB 65 to 70 PLdB 65 to 70 PLdB low - boom flight 75 to 80 PLdB overwater flight Airport noise Meet with margin 10 EPNdB 10 to 20 EPNdB (cum below Chapter 4 ) Cruise emissions Equivalent to subsonic <10 <5 and particulate and water vapor (cruise NO g/kg of fuel) x mitigation Performance goals Cruise speed Mach 1.6 to 1.8 Mach 1.6 to 1.8 Mach 1.3 to 2.0 Range (n mi) 4000 4000 4000 to 5500 Payload (passengers) 6 to 20 35 to 70 100 to 200 Fuel efficiency 1.0 3.0 3.5 to 4.5 (pass - miles per lb of fuel) www.nasa.gov National Aeronautics and Space Administration
Objectives
• Investigate benefits of offset nozzles for N+2 supersonic
vehicles.
• Conduct engine parametric study to identify design criteria for
meeting performance and noise goals.
• Use model scale experimental data to investigate perceived noise
reduction of jet noise at full scale for takeoff conditions.
• Determine the best azimuthal orientation of offset nozzles to
minimize lateral takeoff jet noise.
• Investigate an alternative takeoff procedure called “programmed
lapse rate” (PLR) for noise reduction.
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Aircraft Noise Assessments
Offset Nozzle Orientations Lockheed Martin “1044” Aircraft Morgenstern , J., et al., “Advanced Concept Studies for Supersonic Commercial Transports Engine Service in the 2018 - 2020 Period Phase 2,” NASA CR - 2015 - 218719, July 2015.
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Engines for Parametric Study
Variable Cycle Engine (VCE) Mixed Flow Turbofan (MFTF) www.nasa.gov National Aeronautics and Space Administration
Engine Parametric Study
Each symbol represents a different combination of engine Overall Pressure Ratio (OPR), main engine bypass and throttle ratio, and design bypass ratio of the third stream (BPRt ).
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Experimental Data
Core nozzle pressure ratio, NPRc: 1.5 to 2.3 Bypass nozzle pressure ratio, NPRb: 1.5 to 2.3 Tertiary nozzle pressure ratio, NPRt: 0, 1.0 to 2.1 Core nozzle temperature ratio, NTRc: 3.0 Free jet Mach 0.30 Bypass - to - core area ratios, Ab/Ac: 1.0, 2.5 Axisymmetric Offset Henderson , B., Leib, S., and Wernet, M., “ Measurements and Predictions of Noise from Three - Stream Jets,” AIAA - 2015 - 3120 and NASA/TM - 2015 - 218848, 2015 .
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Single Engine Full - Scale One - Third Octave Spectra
Supersonic Core NPRc = 2.1 Ab/Ac = 2.5 Ab/Ac = 1.0 Subsonic Core NPRc = 1.8 www.nasa.gov National Aeronautics and Space Administration
Noise Certification
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Model Data versus Flight Data
Model Scale 112.1 EPNdB Learjet 113.5 EPNdB 2 EPNdB Offset Used for Predictions Brown , C. and Bridges, J, “An Analysis of Model Scale Data Transformation to Full Scale Flight Using Chevron Nozzles,” NASA TM - 2003 - 212732, 2003.
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Perceived Noise Levels for Offset Jets
NPRb = 1.8 NTRc = 3.0 plug c b t 99.3 EPNdB (Chapter 3) www.nasa.gov National Aeronautics and Space Administration
Programmed Lapse Rate (PLR)
Lateral Point Flyover Point • Thrust is reduced by 10% at lateral certification point.
• Small change in altitude • Flyover conditions are same for both procedures.
• NOT APPROVED BY FAA!
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Single Engine Flyover
NPRc = 1.8 NPRt = 1.6 Ab/Ac = 2.5 www.nasa.gov National Aeronautics and Space Administration
Effective Perceived Noise Levels
NPRc = 1.8 NPRt = 1.6 Ab/Ac = 2.5 www.nasa.gov National Aeronautics and Space Administration
Conclusions (1 of 2)
• For the engines evaluated, a VCE with three - streams and
maximum mission range is predicted to have jet noise levels that
are 8 to 10 EPNdB higher than a lower specific thrust dual - flow
MFTF .
- The MFTF is predicted to have a range that is about 100 miles less than the VCE.
- Larger diameter lower expansion ratio nozzles associated with the MFTF could adversely impact sonic boom signatures .
• Separate flow, offset nozzles reduce the noise directed toward
the thicker side of the outer flow stream .
• The noise reduction benefits from offset nozzles due to
azithmuthal directivity become less as NPRc is reduced. Results
show that there is a 1.3 to 1.5 EPNdB benefit for NPRc = 2.1, and
a 0.6 to 0.8 EPNdB benefit for NPRc = 1.8 .
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Conclusions (2 of 2)
• It is unlikely that offset nozzles will provide enough noise
reduction for the highest range VCE considered in the engine
parametric study to be quieter than a dual - stream MFTF with a
lower NPRc .
• For a three - engine N+2 aircraft with full throttle takeoff, there is a
1.4 EPNdB margin to Chapter 3 noise regulations predicted for
the lateral certification point .
- Best case offset nozzle configuration with NPRc = 1.8, NPRb = 1.8, NPRt = 1.6, NTRc = 3.0 and Ab/Ac = 2.5 .
• With a 10% PLR, the margin increases to 5.5 EPNdB and is
sufficient to meet Chapter 4 regulations .
- Depending on the cumulative split across certification points, can meet the new Chapter 14 noise levels - However , it is standard practice to have at least a 4 EPNdB additional cumulative margin for growth versions of the aircraft .
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Recommendations
• Further research should focus on noise reduction technologies
for low specific thrust engines applied to supersonic aircraft, including their impact on sonic boom.
Acknowledgments
This work was supported by NASA’s Commercial Supersonic
Technology (CST) project in the Advanced Air Vehicles Program.
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