Simulation study on exhaust noise of a rocket engine with different thrust and jet types

DOI:	10.11809/bqzbgcxb2023.01.004
Keywords:	rocket engine; thrust; exhaust; under expanded; over expanded; aerodynamic noise
Abstract:	The aerodynamic noise analysis of rocket engine exhaust is the basis of noise reduction. In this paper, the k ε turbulence model and large eddy simulation are used to simulate the engine exhaust field, and then the FW H method is used to calculate the noise field. The simulation analysis of under expansion and over expansion exhaust flow fields of four different thrust engines shows that the distribution of sound power level in the exhaust field is similar to that of turbulence intensity, and there is an obvious boundary; the sound power level presents the characteristics of conical distribution in the jet influence area, and the half cone angle increases with an increase of the thrust, but changes little, ranging from 13° to 16°. The sound power is the highest after the normal shock wave. In addition, the position with the highest noise intensity is between the interface with Mach number 1 and the gas/air interface. When the jet is under expanded, the maximum sound power is at the downstream of the nozzle outlet. When the jet is over expanded, the maximum sound power is near or inside the nozzle. For the engine exhaust field with similar thrust, the noise pressure level is basically the same, which is independent of the jet state. With the increase of engine thrust, the maximum sound power level does not increase much, while the expansion of the range of high sound power level is the main reason for the increase of noise. The frequency range of engine exhaust noise is wide. The reason why the main frequency decreases with the increase of thrust is not the decrease of high frequency noise, but the enhancement of low frequency noise caused by large scale downstream vortex pulsation.
Issue:	Vol. 44 No. 1 (2023)
Published:	2023-01-28
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