吊挂安装效应对热喷流噪声影响实验

This experiment was made to study the installation effect on the radiated noise from separate flow nozzles with a bypass ratio of 5.5 at take-off condition, as well as the jet noise reduction of pylon-based chevron nozzles. All the experiments were conducted on the hot jet noise rig located in the anechoic chamber. The results indicated that the pylon made an azimuthal dependence on the far field radiated jet noise frequency spectrum. The pylon was effective at low-frequency with reducing noise but produced an increase of noise at high-frequency. The most significant low-frequency noise reduction was observed in position located above the pylon where the peak noise reduction was 3.7dB on frequency spectrum. There was little effect of chevron nozzles on the jet noise radiated from the top of the pylon. The low-frequency noise reduction on the pylon was observed below and laterally while the position below the pylon had the best low-frequency noise reduction whose peak noise reduction was about 1.3dB on frequency spectrum. The largest impact of pylon on high-frequency noise was only on the side. The installation had little effect on the far field overall sound pressure level directivities.