Experimental and numerical studies of the aeroacoustics of axisymmetric supersonic inlets

Abstract

A series of experiments were conducted at an outdoor facility to evaluate the aerodynamic and acoustic performance of a supersonic inlet with a modified auxiliary door geometry. A 1/14 scale model of an axisymmetric, mixed-compression, supersonic inlet designed for civil transportation (P-inlet) was used in conjunction with a 10.4 cm (4.1 in) turbofan engine simulator, to test a new auxiliary door geometry designed to reduce engine fan noise radiated to the forward sector. The flow distortion at the fan face was reduced by modifying the auxiliary inlet doors. The new door geometry uses door passages with increased circumferential span to improve the distribution of the flow entering through the doors. To provide a basis for comparison, a baseline inlet with an auxiliary door geometry representative of the original designs was also tested. The results show that the new door geometry is successful in reducing circumferential distortion of the flow Mach number near the fan face by 30% compared to the baseline configuration. In addition, far field radiation of the blade passing frequency tone and overall noise is reduced by an average of 4 dB (SPL)in the forward sector (0° to 110° from the inlet axis). A 3-D, viscous numerical simulation of the baseline door configuration reveals a large region of flow separation downstream of the auxiliary door. This flow separation leads to a significant increase in circumferential distortion at the fan face.