高声强下金属丝网声衬线性特性及声阻抗模型研究

Acoustic liner is the most important noise control technique in aero-engine nacelle. With the increase of engine and nacelle low weight and low noise requirement, wire mesh liner with fine tonal noise attenuation capability and wider broadband noise attenuation characteristics attracts more and more research attention. However, lack of the capture of wire mesh micro flow phenomenon influences the understanding of acoustic energy dissipation mechanism. Hence, present impedance model mainly based on empirical model, which unable to describe linear characteristics of wire mesh liner under high sound pressure level through physics. To overcome the difficulty, this project would study the linear characteristics and impedance model of wire mesh liner under high SPL by numerical simulation and theoretical investigation. Advance Direct Numerical Simulation (DNS) technique is to be employed for numerical simulation in the conjunction with a highly accurate Computational Aero-Acoustics (CAA) approach. Multi-time-step strategy and multi-scale mesh technique is applied to achieve an efficient numerical method to precisely introduce the micro flow phenomena of wire mesh liner with different porosity under high SPL. Through the insight analysis of acoustic energy dissipation mechanism, linear characteristics of wire mesh liner is expected to be uncovered and illustrated. With the cooperation of theoretical study, wire mesh liner impedance model based on physics is able to be established, which would provide theoretical foundation for high performance acoustic liner design.

声衬是航空发动机消声短舱中最重要的噪声控制手段，而随着发动机和短舱轻量化要求以及降噪指标的不断提高，具备良好的单频降噪特性和更宽的降噪频带等高吸声性能特性的金属丝网声衬成为研究关注的焦点。然而由于缺乏对金属丝网声衬微流动现象的精细捕捉影响了对其声能耗散机理的认识，以致目前已有的阻抗预测模型主要以经验模型为主，无法由物理机理出发更为准确的描述高声强下金属丝网声衬的线性特性。因此，本项目拟采用数值模拟与理论研究相结合的方法，深入研究高声强条件下金属丝网声衬线性特性及其声阻抗模型。数值模拟将基于直接数值模拟策略和高精度计算气动声学方法，采用多时间步方法和多尺度网格技术相结合的高效计算方法，以精确刻画高声强下不同孔隙尺寸的金属丝网声衬的微流动现象，分析研究其声能耗散机理以解释其高声强下的线性特性，并与理论方法结合建立起基于物理的声阻抗预测模型，为高效声衬设计提供理论依据。

通过为期三年的研究，本项目研究团队完成了所有计划和研究目标。主要发展了基于直接数值模拟策略的高精度计算气动声学方法，该方法采用多时间步与多尺度网格技术。通过高精度数值模拟分析了高声强下小孔隙尺寸的金属丝网线性特性，研究了金属丝网声能耗散机理，解释其高声强下的线性特性，并结合理论方法和实验数据，建立了半经验声阻抗模型，搭建声阻抗模型框架并完成程序实现，形成了完整的理论体系和工具方法。研究成果已经应用于民用航空发动机短舱声衬设计中。