150摩托車(chē)消聲器改進(jìn)設(shè)計(jì)（本科畢業(yè)論文設(shè)計(jì)）

摘  要

    機(jī)動(dòng)車(chē)輛的噪聲是城市道路噪聲的主要來(lái)源，而發(fā)動(dòng)機(jī)排氣噪聲是機(jī)動(dòng)車(chē)的主要噪聲源之一，使用排氣消聲系統(tǒng)則是降低發(fā)動(dòng)機(jī)排氣噪聲的最有效途徑，所以排氣消聲系統(tǒng)在降低機(jī)動(dòng)車(chē)噪聲中起著至關(guān)重要的作用，這就要求消聲器的消聲性能要進(jìn)一步提高。
    本文介紹了用邊界元法對(duì)150cc摩托車(chē)的消聲器進(jìn)行聲學(xué)仿真分析，并對(duì)其進(jìn)行改進(jìn)，提高它的消聲性能。包括用UG建立起消聲器的三維模型，再用HyperMesh對(duì)模型進(jìn)行網(wǎng)格的劃分，最后用SYSNOISE進(jìn)行聲學(xué)仿真分析，算出它的傳聲損失。
    在改進(jìn)中，根據(jù)分析結(jié)果，得知消聲性能主要是在中低頻較差，而根據(jù)第一腔分析的結(jié)果可知第一腔主要消中低頻噪聲，所以針對(duì)第一腔進(jìn)行結(jié)構(gòu)上的改進(jìn)。改進(jìn)方法是將第一腔改為插入式擴(kuò)張腔，具體的方法是在管上穿孔，穿孔率要大于25%，用SYSNOISE分析的結(jié)果證明改進(jìn)方法是正確的。

關(guān)鍵詞：消聲器，邊界元法，傳聲損失，插入式擴(kuò)張腔

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   錄

中文摘要 Ⅰ
ABSTRACT Ⅱ
1 緒論 1
1.1 課題研究意義 1
1.2 國(guó)內(nèi)外現(xiàn)狀及分析方法比較 2
1.3研究?jī)?nèi)容 3
本章小結(jié) 4
 2 基本理論 5
 2.1 噪聲產(chǎn)生機(jī)理 5
 2.2消聲器消聲原理 5
 2.3 聲學(xué)理論基本概念 8
 2.4 消聲性能評(píng)價(jià)指標(biāo) 9
 2.5 邊界元基本理論 10
 2.6 邊界元分析實(shí)例 11
 本章小結(jié) 13
 3 消聲器的聲學(xué)分析 14
 3.1 消聲器的UG建模 14
 3.2 模型網(wǎng)格的劃分 17
 3.3 模型的聲學(xué)分析 24
 本章小結(jié) 30
 4 消聲器的改進(jìn) 31
 本章小結(jié) 34
 5 總結(jié) 35
參考文獻(xiàn) 37