火箭发动机超声速过膨胀射流气动噪声特性研究

The large eddy simulation (LES) is used to calculate the shape and near-field sound pressure distribution of an over expanded supersonic jet in rocket engine at different ratios of inlet temperature to ambient temperature. Based on the Ffowcs Williams-Hawkings (FW-H) equation, the noise sources decomposition is used for far-field noise on different positions. And the generation mechanism of supersonic jet noise is analyzed according to the sound pressure level spectrum and turbulence structure. The results show that the aerodynamic noise of the over expanded supersonic jet consists of the turbulent mixed noise and the broadband shock noise. The near-field noise source radiates the medium and high frequency noise in the form of Mach wave to the large azimuth, and the downstream large-scale turbulence structure radiates the low frequency noise to the low azimuth range. The peak frequency of sound pressure level increases with the increase of observation angle, and with the increase of temperature ratio, the radiation angle of Mach wave increases, and the directivity of noise changes. This study can provide reference for acoustic environment design in rocket launch or ground test of rocket engine.