刚性多孔材料低雷诺数流场中高声强吸声性能研究

This research is to investigate sound absorption mechanisms of porous materials at high sound intensities with mean flows, aiming at developing approaches to optimize absorption at a wide frequency bandwidth with possible applications in noise reduction of aircraft engine liners. Porous metals or ceramics or their composites possess not only applicability to the adverse environment of aircraft engine liners and other industrial silencers but also wider absorption frequency bandwidths compared to traditional honeycomb liners. However, there is a need of systematic studies both of theoretical and experimental for such materials as their absorption mechanisms are unlikely to be the same as of honeycomb with perforates, chiefly due to their complex porous structures and operation conditions, such as mean flows and high sound intensities. Although recently there has been some relevant experimental studies, there is still a lack of fundamental knowledge of their absorption mechanisms. Therefore, this research will concentrate on how vortex and sound interact in porous materials with pore sizes of microns in a mean flow at high sound intensities, how porous material nonlinearity affects sound propagation, and in the end what technically possible new materials and approaches could improve noise reduction in aircraft engine liners as well as industrial silencers under similar operation conditions.

本项目以航空发动机声衬降噪为背景，研究多孔材料在有附加流场与高声强声场情况下的吸声机理，用以开发扩展声衬吸声带宽为目标的吸声优化方法。传统蜂窝结构声衬存在吸声频带偏窄的问题，而多孔金属或陶瓷或其复合材料不仅适合航空发动机声衬及其它工业消声器工作环境且具有宽带吸声的特点。但是由于多孔材料内部结构复杂，各种不同孔隙拓扑构型，高声强特别是在附加流场作用下的吸声机制与穿孔板不尽相同，需要深入系统的理论与实验研究。目前有关多孔金属在高声强声场及表面附加切向流场作用下的声学特性研究有些实验，但机理研究还不多，因此本项目拟在理论上进一步深入研究，特别是有平均流影响时微米量级孔隙中高声强下的涡声作用机制，以及刚性多孔材料诸如金属或陶瓷或其复合材料的材料非线性对声波传播的影响，并在技术上探讨为航空发动机和类似工作条件的工业消声器提供高效降噪的可能新材料和新途径。

本项目以航空发动机声衬降噪为背景，研究多孔材料在有附加流场与高声强声场情况下的吸声机理，用以开发扩展声衬吸声带宽为目标的吸声优化方法。传统蜂窝结构声衬存在吸声频带偏窄的问题，而多孔金属或陶瓷或其复合材料不仅适合航空发动机声衬及其它工业消声器工作环境且具有宽带吸声的特点。但是由于多孔材料内部结构复杂，各种不同孔隙拓扑构型，高声强特别是在附加流场作用下的吸声机制与穿孔板不尽相同，需要深入系统的理论与实验研究。目前有关多孔金属在高声强声场及表面附加切向流场作用下的声学特性研究有些实验，但机理研究还不多。在本项目研究中我们初步建立了有平均流影响时以圆柱阵列为基础的微米量级孔隙中高声强下的涡声作用计算模型，并建立了基于激光多普勒测速LDV的声学流管以进行多孔声衬的声学实验，为在技术上探讨为航空发动机和类似工作条件的工业消声器提供高效降噪的可能新材料和新途径提供理论基础。