基于非对称吸声器的发动机声学超表面声衬

Metasurface acoustic liner of engine based on asymmetric absorber

为了解决发动机低频噪声问题,基于双端口非对称吸声器原理,设计了一种尺寸渐变的吸声超表面,用于发动机声衬降噪设计.首先,建立了非对称共振吸声器的理论分析模型和仿真分析模型,揭示了降噪机理,并分析了其降噪效果的影响因素.然后基于非对称共振吸声器设计了一种声学超表面声衬,用全模型理论计算、等效阻抗理论计算和COMSOL有限元仿真三种方法深入分析了声衬的降噪效果,并用全模型理论计算和等效阻抗理论计算方法考虑了流速对降噪效果的影响,然后对此结构进行了参数优化.研究结果表明,所设计的基于非对称吸声器的声学超表面声衬在厚度仅为2.5 cm(仅为252 Hz对应波长的1/54)的情况下,可实现252—692 Hz的频带范围内3 dB以上的降噪效果,为发动机降噪设计提供了一种新的设计思路.

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 is 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 analyzed in depth 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 the full model theoretical calculation and equivalent impedance theoretical calculation.The research results show that the acoustic metasurface acoustic liner designed based on asymmetric sound absorber can achieve noise reduction effect of more than 3 dB in a frequency band range from 252 to 692 Hz when the thickness is only 2.5 cm(only 1/54 of the corresponding wavelength of 252 Hz),which provides a new idea for designing engine noise reduction.