高切向流速高声强条件下梯度阻抗吸声超材料研究

Gradient impedance sound absorbing metamaterial under high tangential flow velocity and high sound intensity

在涡扇航空发动机声衬表面,存在高速切向流场与高声强声场耦合问题,吸声机理与调控机制复杂。高切向流速高声强条件下低频宽带噪声的有效吸收极具挑战性。该研究提出考虑高切向流速、高声强以及复杂容抗修正的声阻抗理论方法,设计了梯度阻抗调控吸声超材料。从理论解析计算、有限元数值建模及试验测试三个维度深入分析声波与结构的作用机理和调控规律。结果表明:梯度阻抗吸声超材料可有效提高吸声效率,避免传统声衬吸声频带窄的缺点。在0、30 m/s、60 m/s、98 m/s切向流速和130 dB背景噪声下,提出的梯度阻抗吸声超材料在500~3 000 Hz范围内具备良好吸声效果。该超材料结构简单,在高切向流速高声强复杂边界条件下,仍有深亚波与宽带吸声特性,具有广阔的应用前景。

On surface of turbofan aeroengine sound liner, there is a coupling problem between high-speed tangential flow field and high sound intensity field, sound absorption mechanism and control mechanism are complex. Effective absorption of low-frequency broadband noise under conditions of high tangential flow velocity and high sound intensity is extremely challenging. Here, a theoretical method of acoustic impedance considering high tangential flow velocity, high sound intensity and complex capacitance correction was proposed, and a gradient impedance regulated sound absorbing metamaterial was designed. The mechanism and regulation laws of sound wave-structure interaction were deeply analyzed from 3 aspects of theoretical analysis, finite element numerical modeling and tests. The results showed that gradient impedance sound absorbing metamaterial can effectively improve sound absorption efficiency, and avoid the disadvantage of narrow sound absorption frequency band of traditional sound liner;under conditions of tangential flow velocities of 0, 30 m/s, 60 m/s and 98 m/s, respectively as well as 130 dB background noise, the proposed gradient impedance sound absorbing metamaterial has good sound absorption effect within the range of 500-3 000 Hz;this metamaterial with simple structure has deep sub-wave and broadband sound absorption characteristics under complex boundary conditions of high tangential flow velocity and high sound intensity, so it has broad application prospects.