Noise Measurements of a Low-Noise Top-Mounted Propulsion Installation for a Supersonic Airliner

[摘要] A model-scale exhaust system was tested to validate low-noise concepts and noise prediction methods. The tests involved far-field acoustics, translating phased array, and particle image velocimetry; this report covers the far-field acoustic measurements. Data were acquired for a series of nozzles with different chevron designs, both uninstalled and installed on a representative aircraft planform. The impact of the various chevron treatments on the far-field noise was documented, along with the impact of the pylon and planform. For the baseline nozzle, installation produced a 2EPNdB reduction, as assumed in system studies. Chevrons were used to shift noise sources upstream to maximize the installation benefits and to reduce unshielded sources downstream. These resulted in reductions of 4-5EPNdB relative to the uninstalled baseline nozzle. Detailed analysis of spectral directivities behind the integrated EPNL metric gave insight into how well these concepts actually work. When correlated with particle image velocimetry measurements and phased array measurements, reported in companion papers, the explanation of acoustic benefits from top-mounted propulsion is clear as is the path toward optimization of the concept.

[发布日期] 2019-01-07

[学科分类] 声学和超声波

[关键词] ACOUSTIC MEASUREMENT;ACOUSTIC PROPERTIES;AEROACOUSTICS;AERODYNAMIC NOISE;EFFECTIVE PERCEIVED NOISE LEVELS;EXHAUST SYSTEMS;FAR FIELDS;FLOW DISTRIBUTION;JET AIRCRAFT NOISE;NOISE GENERATORS;NOISE PREDICTION;NOISE REDUCTION;PARTICLE IMAGE VELOCIMETRY;PHASED ARRAYS;PLANFORMS;PREDICTION ANALYSIS TECHNIQUES;PROPULSION SYSTEM PERFORMANCE;TURBULENT JETS