150摩托车消声器改进设计（本科毕业论文设计）.doc

150摩托车消声器改进设计（本科毕业论文设计）

摘  要

    机动车辆的噪声是城市道路噪声的主要来源，而发动机排气噪声是机动车的主要噪声源之一，使用排气消声系统则是降低发动机排气噪声的最有效途径，所以排气消声系统在降低机动车噪声中起着至关重要的作用，这就要求消声器的消声性能要进一步提高。
    本文介绍了用边界元法对150cc摩托车的消声器进行声学仿真分析，并对其进行改进，提高它的消声性能。包括用UG建立起消声器的三维模型，再用HyperMesh对模型进行网格的划分，最后用SYSNOISE进行声学仿真分析，算出它的传声损失。
    在改进中，根据分析结果，得知消声性能主要是在中低频较差，而根据第一腔分析的结果可知第一腔主要消中低频噪声，所以针对第一腔进行结构上的改进。改进方法是将第一腔改为插入式扩张腔，具体的方法是在管上穿孔，穿孔率要大于25%，用SYSNOISE分析的结果证明改进方法是正确的。

关键词：消声器，边界元法，传声损失，插入式扩张腔

ABSTRACT

    The vehicle noise is the main source of the road noise, and the exhaust noise of the engine is the main source of the vehicle noise. The best way of reducing exhaust noise is using the noise elimination system, the noise elimination system plays a very important role in the reducing vehicle noise, so it is requires that upgrading the noise elimination capability of the muffler.
    It introduces that using acoustics emulational method to analyze the 150cc’s motorcycle muffler with the boundary element, and improving the muffler to upgrade the noise elimination capability in this paper. Involve establishing the muffler’s three-dimensional model with UG, meshing the model with HyperMesh, and analyzing the model with SYSNOISE to get the transmission loss.
    In the process of the improving, it can know that the main weakness of the noise elimination capability of the muffler is focus on the mid-frequency and the low- frequency through analyzing the result. And through analyzing the first cavity to know that the first cavity plays a main role in the mid-frequency and the low- frequency, so it needs to modify the first cavity’s structure. The method of the improving is turning the first cavity into the Insert Expanding Cavity, and the practical method is perforation, the percentage of the perforation must be over 20%, and the result of analyzing with the SYSNOISE prove that the method of the improving is right.

Key Words：Muffler, Boundary element method, Transmission loss, Insert expanding cavity

目   录

中文摘要 Ⅰ
ABSTRACT Ⅱ
1 绪论 1
1.1 课题研究意义 1
1.2 国内外现状及分析方法比较 2
1.3研究内容 3
本章小结 4
 2 基本理论 5
 2.1 噪声产生机理 5
 2.2消声器消声原理 5
 2.3 声学理论基本概念 8
 2.4 消声性能评价指标 9
 2.5 边界元基本理论 10
 2.6 边界元分析实例 11
 本章小结 13
 3 消声器的声学分析 14
 3.1 消声器的UG建模 14
 3.2 模型网格的划分 17
 3.3 模型的声学分析 24
 本章小结 30
 4 消声器的改进 31
 本章小结 34
 5 总结 35
参考文献 37