125摩托车消声器结构分析与改进（本科毕业论文设计）.doc

125摩托车消声器结构分析与改进（本科毕业论文设计）

摘    要

传统的排气系统内消声器设计主要根据一维平面波理论，但是该理论难以正确模拟三维的波动，计算结果不准确。有限元三维数值方法能对消声器准确的模拟，是改进设计的有效方法。
本文针对某125摩托车的消声器，采用有限元方法建立声学模型。对模型进行声学分析，并提出改进方案。
首先对简单扩张腔进行一维和三维有限元方法的计算，并进行了比较，得出了三维方法的准确性的结论，并简单总结了消声器内部结构对消声性能的影响，为以后的改进打下了基础。
然后，在UG环境下建立原消声器的三维几何模型，并对模型进行几何清理，网格划分，在SYSNOISE中计算得到消声器的传递损失曲线。并对原消声器进行分腔计算，得到各腔的传递损失曲线。
根据原消声器整体和分腔的传递损失曲线，把改进的重点放在增强消声器的低频消声量上。
对消声器内部结构进行了多种方法的改进。为了提高低频消声效果，在原消声器后加了一共振腔，计算结果表明新的改进方案基本满足改进要求。

关键词：有限元，消声器，传递损失

ABSTRACT

Most of muffler design methods developed earlier have dealt primarily with one-dimensional-plan wave theory. But the theory is hard to provide accurate analysis result because of the effect of the three-dimensional wave. The three dimensional numerical method such as the finite element method can simulate muffler accurately. So it is an effective method to improve design.
In this thesis, an acoustics model of muffler is built by the Finite Element Method (FEM) based on a muffler of 125 type of motorcycle, after that the acoustics characteristic analysis is done and some improvements are achieved.
Firstly, a single expansion chamber muffler is calculated by one-dimensional FEM and three-dimensional FEM respectively. The comparison of the experimental data of two methods indicates that three-dimensional FEM is more accurate. It also briefly points out the effect of the internal structure of the muffler on the performance of the muffler.
Then, the three-dimensional model of the original muffler is built by UG. After the clean-up and mesh job have been finished, the transmission loss (TL) curve can be got by SYSNOISE. Then the TL curve of each cavity of the original muffler can be got by calculating the TL in each cavity of the muffler.
Next, put the emphasis of the improvement on enhancing the volume of low-frequency noise reduction of the muffler according to the TL curve of the whole muffler and the cavities of the muffler.
Finally, numerous methods are implemented to improve the internal structure of the muffler. A resonator is added to the original muffler in purpose of improving the effects of low-frequency noise reduction, and the result of this new method meets the basic requirement of the goal.

Keywords: FEM, muffler, Transmission loss

目   录

中文摘要 Ⅰ
ABSTRACT Ⅱ
1绪论 1
  1.1研究背景及目的意义 1
  1.2消声器国内外研究现状 2
  1.3本文的研究内容 3
 2基本理论﹑分析方法和软件 5
2.1声学基本概念 5
2.2排气噪声的产生 6
2.3三维数值方法 6
2.4 UG介绍 7
2.4.1主要功能 8
2.4.2主要应用模块 8
2.5 HyperMesh介绍 9
2.5.1 HyperMesh的特点 9
2.5.2 CAD接口及几何模型整理 9
2.5.3模型创建和编辑 10
2.6 SYSNOISE介绍 10
2.7本章小结 11
 3消声器的基本性能 12
3.1引言 12
3.2消声器的分类 12
3.3消声器性能的评价指标 12
3.4简单消声器内部结构对消声性能的影响 13
3.5简单扩张腔的数值分析 14
3.5本章小结 15
 4消声器整体的消声性能分析 17
4.1引言 17
4.2消声器的三维几何模型的建立 17
4.3利用HyperMesh建立有限元模型 17
4.4声学性能分析 18
4.5本章小结 20
 5消声器的分腔性能计算 21
5.1引言 21
5.2消声器的分腔 21
5.3对消声器的前腔进行计算分析 21
5.4对消声器的前腔进行计算分析 22
5.5本章小结 23
 6对原消声器的结构改进 24
6.1引言 24
6.2消声器结构改进 24
6.2.1改进方案一——增加插入管长度 24
6.2.2改进方案二——改变前腔入口插入管和出口插入管长度 25
6.2.3方案三——增加前腔的长度 26
6.2.4方案四——增加后腔的长度 27
6.2.5方案五——增加共振腔 28
6.3本章小结 31
 7结论 32
 致    谢 33
参考文献 34