发动机排气消声器的性能仿真

车辆工程专业毕业文档，文档编号:JX902  文档字数:19562.页数:40

摘    要
 排气噪声是汽车及其内燃机的主要噪声源之一，在内燃机整机噪声中，排气噪声往往比其它噪声高出10~15dB(A)左右。目前国内外减少排气噪声最有效、最直接的方法是安装排气消声器。因此，研究排气消声器消声性能对消声器的改进设计以及降低排气噪声有着重要的意义。
 本文总结推导了消声器声学基本元件的传递矩阵。基于传递矩阵法计算分析了简单扩张式和内插管扩张式消声器的结构参数对消声器消声性能的影响规律。仿真结果表明:气流速度小于35m/s左右时，气流速度对消声器的消声性能影响不大;当气流速度大于35m/s左右时，随气流速度增大消声量急剧下降。此外，不同的结构参数对消声性能也有重要的影响。
 论述了消声器的评价指标(插入损失、传递损失、功率损失)，建立排气消声器插入损失数学计算模型。应用MATLAB数学计算软件编制程序计算分析了不同结构参数情况下，简单扩张式消声器插入损失，内插管扩张式消声器的插入损失。
关键字：排气噪声 消声器 简单扩张式 内插管扩张式 插入损失

ABSTRACT
 The exhaust noise is the most main noise source of automobile and evenits internal combustion engine，often is about 10~15dB(A) higher than entire noise of the internal combustion engine in which exhaust noise isn’t included. At Present，it is the most effeetive and direct method to install the exhaust silencer to reduce the exhaus tnoise.Therefore，the researehed exhaust silencer have the vital significance to reduce the exhaust noise.
 The present paper，summarized and infered transition matrix of acoustie primary element of silencer.By method of transition matrix，computed and analyzed effcet of structure paremeter in the simple expansion type silencer and insert tube expansion type silencer to acoustic performance:Computed and analysed effcet of designed parameter in Helmholtz wave resonating silencer and perforated pipe resonating silencer to noise elimination performance. The analysed conelusions show:When the stream veloeity is smaller than about 35m/s，the stream veloeity is not big effect to noise elimination Performance:When the stream velocity is bigger than about 35m/s，along with the stream velocity increasing noise elimination Performance Suddenly drop.In addition，the different design Parameter has the important influence to the noise elimination Performance as well.
 Discusses the evaluation of the muffler (insertion loss, transmission loss, power loss), the establishment of exhaust muffler mathematical model of insertion loss. Application of MATLAB mathematical computing software programming structural parameters of different circumstances, the simple expansion-type silencer insertion loss, with expansion-type muffler tube insertion loss.
Key words: Exhaust-noise Muffler  Simple-expansion Intubation-expansion Insertion-loss

目   录
摘    要 i
ABSTRACT ii
目   录 iii
第一章 绪 论 1
1.1噪声概述 1
1.1.1内燃机噪声的产生机理 1
1.1.2噪声危害及控制 4
1.2消声器的类型 6
1.3国内外消声器研究发展状况 7
1.4文档主要工作内容 9
第二章 传递矩阵法与有限元法的基本理论 10
2.1理想流体介质中的声波方程 10
2.2传递矩阵法基本理论 11
2.2.1声、电类比理论 11
2.2.2声压和体积速度的复数表示形式 12
2.2.3声学四端网络 14
2.3基本消声元件的传递矩阵 16
2.4本章小结 19
第三章 抗性扩张式消声器的消声性能仿真分析 21
3.1排气消声器性能的评价 21
3.1.1消声器性能的评价指标 21
3.1.2消声性能一维计算数学模型 22
3.2简单扩张式消声器的消声性能分析 24
3.2.1扩张比对消声器插入损失的影响 25
3.2.2扩张腔长度对消声器插入损失的影响 27
3.2.3尾管长度对消声器插入损失的影响 28
3.3内插管扩张式消声器的消声性能分析 28
3.3.1内插管扩张式与单扩张式消声器插入损失的比较 30
3.3.2前后内插管不同匹配对消声性能的影响 30
3.4气流速度和温度对消声性能的影响 31
3.5本章小结 33
第四章 总结和展望 34
4.1总 结 34
4.2工作展望 34
参考文献 35
致    谢 36

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