Research on Metasurface Acoustic Liner of Engine Based on Asymmetric Absorber

In order to solve the problem of low frequency noise of engine, based on the principle of dual port asymmetric sound absorber, a kind of gradually changing size sound absorbing metasurface was designed to reduce the noise of engine acoustic liner. Firstly, the theoretical analysis model and simulation analysis model of the asymmetric resonance sound absorber are established, the noise reduction mechanism is revealed, and the influencing factors of the noise reduction effect are analyzed. Then an acoustic metasurface acoustic liner is designed based on the asymmetric resonance sound absorber. The noise reduction effect of the acoustic liner is deeply analyzed by using three methods: full model theoretical calculation, equivalent impedance theoretical calculation and COMSOL finite element simulation.Then, the parameters of this structure are optimized, and the influence of flow velocity on the noise reduction effect is considered by using full model theoretical calculation and equivalent impedance theoretical calculation. The research results show that the designed acoustic metasurface acoustic liner based on asymmetric sound absorber can achieve noise reduction effect of more than 3dB in the frequency band range of 252Hz to 692Hz when the thickness is only 2.5cm (only 1/54 of the corresponding wavelength of 252Hz), which provides a new design idea for engine noise reduction design.