125摩托車消聲器結構分析與改進（本科畢業(yè)論文設計）

摘    要

傳統(tǒng)的排氣系統(tǒng)內消聲器設計主要根據一維平面波理論，但是該理論難以正確模擬三維的波動，計算結果不準確。有限元三維數(shù)值方法能對消聲器準確的模擬，是改進設計的有效方法。
本文針對某125摩托車的消聲器，采用有限元方法建立聲學模型。對模型進行聲學分析，并提出改進方案。
首先對簡單擴張腔進行一維和三維有限元方法的計算，并進行了比較，得出了三維方法的準確性的結論，并簡單總結了消聲器內部結構對消聲性能的影響，為以后的改進打下了基礎。
然后，在UG環(huán)境下建立原消聲器的三維幾何模型，并對模型進行幾何清理，網格劃分，在SYSNOISE中計算得到消聲器的傳遞損失曲線。并對原消聲器進行分腔計算，得到各腔的傳遞損失曲線。
根據原消聲器整體和分腔的傳遞損失曲線，把改進的重點放在增強消聲器的低頻消聲量上。
對消聲器內部結構進行了多種方法的改進。為了提高低頻消聲效果，在原消聲器后加了一共振腔，計算結果表明新的改進方案基本滿足改進要求。

關鍵詞：有限元，消聲器，傳遞損失

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   錄

中文摘要 Ⅰ
ABSTRACT Ⅱ
1緒論 1
  1.1研究背景及目的意義 1
  1.2消聲器國內外研究現(xiàn)狀 2
  1.3本文的研究內容 3
 2基本理論﹑分析方法和軟件 5
2.1聲學基本概念 5
2.2排氣噪聲的產生 6
2.3三維數(shù)值方法 6
2.4 UG介紹 7
2.4.1主要功能 8
2.4.2主要應用模塊 8
2.5 HyperMesh介紹 9
2.5.1 HyperMesh的特點 9
2.5.2 CAD接口及幾何模型整理 9
2.5.3模型創(chuàng)建和編輯 10
2.6 SYSNOISE介紹 10
2.7本章小結 11
 3消聲器的基本性能 12
3.1引言 12
3.2消聲器的分類 12
3.3消聲器性能的評價指標 12
3.4簡單消聲器內部結構對消聲性能的影響 13
3.5簡單擴張腔的數(shù)值分析 14
3.5本章小結 15
 4消聲器整體的消聲性能分析 17
4.1引言 17
4.2消聲器的三維幾何模型的建立 17
4.3利用HyperMesh建立有限元模型 17
4.4聲學性能分析 18
4.5本章小結 20
 5消聲器的分腔性能計算 21
5.1引言 21
5.2消聲器的分腔 21
5.3對消聲器的前腔進行計算分析 21
5.4對消聲器的前腔進行計算分析 22
5.5本章小結 23
 6對原消聲器的結構改進 24
6.1引言 24
6.2消聲器結構改進 24
6.2.1改進方案一——增加插入管長度 24
6.2.2改進方案二——改變前腔入口插入管和出口插入管長度 25
6.2.3方案三——增加前腔的長度 26
6.2.4方案四——增加后腔的長度 27
6.2.5方案五——增加共振腔 28
6.3本章小結 31
 7結論 32
 致    謝 33
參考文獻 34