动力机械降噪研究

论文总字数：29745字

摘 要

关键词:声波；声场；噪声控制；结构振动；消音器；发动机

A STUDY ON NOISE CONTROL OF POWER MACHINERY

03011419 CaoTing

Supervised by TanPing

Abstract：Power machinery is widely used in various sectors of industry, agriculture, transportation As the increasing demand of better environment of people more and more power machinery noise have attracted people’s attention, It is not only harm to the machine itself, but also exposure a strong noise to the outside world. It will do harm to people’s health .Now, noise pollution has become an important factor affecting people's life and production, and the problem of noise emissions and noise pollution control growing about power generator, therefore, power generator noise reduction research is significant. In this paper include a detailed study about engine noise control technology through theoretical demonstration, research and test. Starting from the basic acoustic theory to explain some of the basic properties of sound waves, and then discuss the situation in the different forms of sound propagation tube, to get sound transmission coefficient in different tubes and finally to arrive to the expansion-type silencer designing methods . After that, combined with the engine of car, the aerodynamic noise and structural vibration noise theory are discussed. Based on the analysis of aerodynamic noise, we studied the major part of it that is the exhaust noise, and then discussed the mechanism and its influencing factors. The last of the paper describes the structure of the engine vibration and noise theory, and it gives the engine structural optimization methods and the design of acoustic cover note.

Key words: sound ；sound field ； noise control；structural vibration ；silencer；engine

目 录

摘要 I

Abstract II

第一章 绪论 1

1.1 动力机械降噪研究背景 1

1.2 本文的主要工作 1

第二章 声波的基本性质 2

2.1 概述 3

2.2 声压的基本概念 3

2.3理想流体媒质的三个基本方程 3

2.3.1 运动方程 4

2.3.2连续性方程 4

2.3.3物态方程 5

2.4 平面声波的基本性质 6

2.4.1波动方程的解 6

2.4.2 声波的传播速度 8

2.4.3声阻抗率与媒质特性阻抗 9

2.5声场中的能量关系 9

2.5.1 声能量与声能量密度 9

2.5.2 声功率与声强 10

2.6 声压级、声强级和声功率级 11

2.7 声波的传播特性 12

第三章 声波在管中的传播 14

3.1声波在两根不同截面的管中传播 14

3.2 中间插管的传声特性 15

3.3扩张管式消音器 16

第四章 无限大障板上圆形活塞的辐射 17

4.1 圆形活塞式辐射器的远场特性 17

4.2 平面辐射器的指向性 18

4.3 近声场特性 19

第五章 空气动力噪声及控制 22

5.1排气噪声产生的机理 22

5.1.1基频噪声 22

5.1.2 气柱共振噪声 22

5.1.3 喷注噪声、紊流噪声和涡流噪声 22

5.1.4亥姆霍兹共振噪声 23

5.2影响发动机排气噪声的主要因素 24

5.3排气消声器 24

5.3.1消声器消声效果的评价 24

5.3.2 消声器的设计依据 25

5.3.3 扩张室式消声器的设计计算 26

5.3.4 消声案例分析......................................................................................................28

第六章 发动机结构振动噪声 30

6.1发动机表面声辐射 30

6.2 发动机结构振动响应 31

6.3 发动机的激振力特性 31

6.4 发动机结构的声学优化 32

6.4.1 发动机机构的声学优化过程 32

6.4.2 发动机结构的声学优化措施 33

6.4.3发动机结构声学优化的基本原则 33

6.5 发动机隔声罩 33

全文总结 35

致谢 36

参考文献 37

1. 绪论

随着工业的发展，动力机械广泛运用于汽车，拖拉机以及各种农业机械，越来越成为不可或缺的基础性行业，对国民经济和人民生活发挥着重要作用，动力机械质量的好坏在一定程度上也决定了其配套产品的性能。

1.1 动力机械降噪研究背景

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