多孔材料的出流和多孔扩散消声理论

多孔扩散消声器是七十年代发展起来的一种新型消声器。它具有体积小、结构简单和较大的减噪本领。目前这种消声器已在国外推广使用,但缺乏理论。本文详细讨论了气流通过多孔材料由于摩擦所产生的压降,提出对多孔材料的阻塞出流可以用材料的有效通道面积和驻点压降来描述。还研究了多孔扩散消声器的原理,认为扩散消声器的噪声能量由两部分组成:一部分是大量小孔喷注所发的噪声;另一部分是小孔喷注汇合成为面积较大速度较低的扩散喷注产生的噪声。在一般情况下,后者是主要的。混合后的噪声可由混合后所形成的喷注中的气流驻点压力(或气流速度)来确定。文中对此做了系统的计算,并列举出多种扩散消声器。根据这些计算,便可以设计满足实用的各种扩散消声器。关键词：

THE OUTFLOW OF AIR FROM POROUS MATERIALS AND THE NOISE REDUCTION THEORY OF POROUS DIFFUSER

Porous diffusers, a distinguished group of silencers, have been developed in the last years, and are used widely in foreign countries. They are preeminent in their small volume, simple structure and high noise reduction. Unfortunately, there are lack of theoretical discussions as yet. In this work, the aerodynamics of flow through porous materials is discused in detail and the authors suggest that the outflow through porous material can be characterized by an effective area and an effective stagnation pressure reduction. Furthermore, the principle of noise reduction of porous diffusers has been studied in some detail, to facilitate the design and the estimation of porous diffusers. Some of the porous diffusers are studied in the light of the present theory.