Noise Reduction of Multinozzle Rocket Jet by Multideck Water Injection

Abstract

During the launch phase of a multinozzle rocket, the high-level noise induced by the supersonic jet ejected from the nozzles significantly affects the structural safety of the rocket and the reliability of the instruments. Therefore, it is important to predict and suppress the multinozzle rocket jet noise. This study proposes a numerical analysis method that uses the detached eddy simulation model combined with species transport equations, the discrete-phase model, and the acoustic analogy method (FW-H). It aims at a four-nozzle liquid rocket to predict jet and noise environments while considering the physical effect of evaporation and the influence of the launch pad structure. The proposed method was verified by comparing the single-nozzle jet simulation and experiment results. The prediction of the supersonic jet flow field and noise environment at different lift-off heights of the rocket was completed. An annular water jet noise-reduction system was designed to suppress the noise environment at different heights by single-deck and double-deck water injections. The noise attenuation effect of the water injection system was better when the lift-off altitude increased. And the noise suppression effect of the double-deck water injection system was more comprehensive than that of the single-deck water injection system. Furthermore, the reasons for the difference in noise reduction by different layers of water injection were analyzed in detail.