摘 要

船舶推进轴系作为整个船舶动力装置的重要组成部分，包括从发动机（机组）输出法兰到推进器之间以传动轴为主的一整套设备。其主要任务是把主机与螺旋桨连接起来，将主机所产生的扭矩传递给后者，同时将螺旋桨产生的轴向推力通过推力轴承传递给船体，以推动船舶前进。船舶推进轴系的稳定运转对于船舶的安全航行具有重大意义。然而推进轴系在实际运转过程中，会受到各种各样的艉部激励作用，进而引发轴系振动。一方面对船舶推进系统造成了损坏，降低了推进轴系的使用寿命；另一方面也影响着船舶的航行安全和船员的日常生活工作。随着船舶日益大型化发展，轴系尺寸大幅增加，艉部激振力剧增，艉部激励引起轴系振动的问题日益突出，因此，开展艉部激励对轴系振动影响的研究显得尤为迫切。

本文提出以某小比例轴系实验台轴系为研究对象，通过仿真计算与实验分析相结合的方法来探讨艉部激励对轴系振动的影响规律，具体研究内容分述如下：

1. 第一章介绍了研究背景与目的、国内外研究现状以及本文主要研究内容。对船舶推进轴系的结构组成、功能和引起轴系振动的原因做了简要介绍，引出了开展艉部激励对轴系振动影响研究的迫切性，进而说明了本文的研究目的；分别从螺旋桨激励、艉轴承-轴颈摩擦激励、船体变形激励三个方面阐述了艉部激励对轴系振动影响的国内外研究现状，最后介绍了本文的主要研究内容。
2. 第二章介绍艉部激励研究的相关理论与方法。分别阐明了艉部激励中的螺旋桨轴承力、艉轴承-轴颈摩擦激励和船体变形激励的成因以及其引起轴系振动的作用机理，同时对有限元法在船舶推进轴系振动研究中的应用和基于快速傅里叶变化（FFT）方法的测试信号频域分析理论做了介绍。

（3）第三章基于仿真计算对艉部激励下轴系强迫振动响应进行了研究。以某小比例轴系实验台轴系为参照，采用有限元软件ANSYS建立该轴系的有限元计算模型，利用模态分析获得了轴系回旋振动、扭转振动、纵向振动的固有振动特性；将轴系受到的艉部激励分解为垂向、横向、轴向的三个分量，通过在艉轴承处对应节点处计入相应方向的载荷来模拟艉部激励的不同分量，基于模态分析的结果，采用谐响应分析来研究轴系在单向艉部激励分量和多向艉部激励分量作用下的强迫振动响应规律，并对仿真结论进行总结。

（4）第四章通过实验分析开展艉部激励对轴系振动特性影响规律的研究。对轴系台架组成、测试方案和实验方案分别做了介绍，基于快速傅里叶变化（FFT）方法对已有轴系台架实验数据进行时域频域转换得到其频谱图，从空载实验、单向艉部激励分量（垂向、横向、轴向）和多向艉部激励分量共计五种工况开展了艉部激励对轴系振动特性的影响规律的分析，并对实验结论进行了总结。

（5）第五章对全文所做的主要工作与相关结论进行了总结，并对后续的研究工作做出了展望。

关键词：艉部激励；推进轴系；振动特性；有限元法；实验分析

Abstract

The propulsion shafting is one of the most important parts of ship’ s power system, it contains the whole equipments from the main engine to the propeller. Its main job is to connect the main engine and the propeller, transfer the torque from main engine to the latter, and transfer the axial propulsion from propeller to the ship hull to drive the ship move forward. The reliability and stabilization of the running propulsion shafting is full of great importance for the vessel’s navigation safety. However, when the propulsion shafting is running, it will be subjected to the various stern excitation which will cause the shafting vibration. On the one hand, this will do great harm to the propulsion system; on the other hand, it will have impacts on the vessel’s navigation safety and crew’s daily life and work. With the ship is becoming larger gradually, the size of propulsion shafting is heavily bigger than before, so that the stern excitation are becoming stronger, the problem of shafting vibration that caused by the stern excitation is becoming more serious.

This paper takes a test platform of reduced propulsion shafting as the research object to carry on the research about influence law of stern excitation on the shafting vibration through methods of simulation calculation and experiment analysis . Main research contents of this paper are as follows:

In chapter 1, the structure composition, main function, vibration cause of the shafting are introduced at first, then the significance about influence law of stern excitation on the shafting vibration and the purpose of this research are introduced. The background are detailed introduced in following aspects: propeller excitation, stern bearing-shaft friction excitation and hull deformation excitation. The main research contents of this paper are introduced finally.

In chapter 2, the cause and mechanism of propeller excitation, stern bearing-shaft friction excitation and hull deformation excitation are detailed introduced. Then the use of finite element method in shafting vibration and frequency domain analysis of test signal that base on Fast Fourier Transform(FFT) are introduced.

In chapter 3, based on the test platform of reduced propulsion shafting, establishing finite element calculation model through ANSYS. The natural frequencies of shaft system are computed by modal analysis. The stern excitation that acting on the shaft is divided into three components: vertical direction, horizontal direction, axial direction. Taking into account the different component of stern excitation on stern bearing, based on the results in modal analysis, carry on the research about forced vibration response of shaft under single direction component of stern excitation and multi-direction components of stern excitation. Finally the analysis conclusions of simulation are summarized.

In chapter 4, the component of shaft platform, test scheme, experiment scheme are introduced at first; based on the FFT method, the experiment data is transformed form time domain to frequency domain, so the spectrogram are got. The research about influence law of stern excitation on the shafting vibration is carried on through five conditions: no-loads; single direction component of stern excitation (vertical direction, horizontal direction, axial direction), multi-direction components of stern excitation. Finally the analysis conclusions of experiment are summarized.

In chapter 5, conclusions of this paper are summarized. Further investigations are also presented.

Key Words：stern excitation; propulsion shafting; vibration characteristics;

finite element method; experimental analysis

目 录

第1章 绪论 1

1.1 研究背景与目的 1

1.1.1 研究背景 1

1.1.2 研究目的 2

1.2 国内外研究现状 2

1.2.1 螺旋桨激励 2

1.2.2 艉轴承—轴颈摩擦激励 3

1.2.3 船体变形激励 4

1.3 主要研究内容 5

第2章 艉部激励基础理论及其研究方法 6

2.1 艉部激励成因与作用机制 6

2.1.1 螺旋桨轴承力 6

2.1.2 艉轴承—轴颈摩擦激励 8

2.1.3 船体变形激励 9

2.2 有限元法在轴系振动中的应用 10

2.3 测试信号频域分析理论 10

2.4 本章小结 11

第3章 基于有限元的艉部激励对轴系振动特性的影响分析 12

3.1 船舶推进轴系的结构介绍与模型建立 12

3.1.1 推进轴系组成及布置 12

3.1.2 轴系有限元模型建立 13

3.2 轴系固有振动特性分析 15

3.2.1 回旋振动固有特性分析 16

3.2.2 扭转振动固有特性分析 17

3.2.3 纵向振动固有特性分析 18

3.3 艉部激励对轴系振动特性的影响分析 19