摘 要

主轴承是船舶柴油机的关键零部件之一，其摩擦功耗占推进轴系总功耗的比重大，一旦出现润滑失效，则容易导致干摩擦，发生轴承烧瓦、抱死等故障，危害柴油机及船舶航行安全。通过研究影响其润滑特性的因素来指导日常管理及轴承设计工作，对提高船舶运营经济性，稳定性都有重要意义。本文以船舶柴油机主轴承为研究对象，利用数值计算方法，对其润滑特性的影响因素进行了研究。

本文首先借助数学计算软件MATLAB对船舶柴油机主轴承无量纲压力进行了求解，对主轴承润滑特性参数进行了计算，探索了轴承长径比、偏心率、轴承半径间隙、轴颈转速、黏压效应对主轴承承载力、摩擦力的影响，并计算了不同偏心率下轴承的偏位角。进而运用网格划分软件ICEM进行了主轴承的网格划分工作，后导入Fluent数值计算软件，着重研究了转速、轴承半径间隙、偏心率、供油口大小、供油压力对主轴承气穴效应和压力场的影响。主要研究结果如下：

1. 主轴承承载力和摩擦力随偏心率的增长而变大，同一偏心率下，二者随长径比的升高而增大。主轴承承载力和摩擦力均随转速的增长呈线性增长趋势，增长速率随偏心率的增长而变大，同一转速下，二者随偏心率的变大而增大。
2. 主轴承承载力和摩擦力随轴承半径间隙的增大而减小，但减小速率随半径间隙的变大而降低。同一轴承半径间隙下，二者随偏心率的增长而变大。在轴承半径间隙小于0.6mm时，黏压效应对主轴承摩擦力影响较大。
3. 对主轴承气穴效应的研究表明随着转速、偏心率的增大，平均气化强度变大，油膜内气相区域有增大的趋势，气穴效应增强。随着供油口面积、供油压力、轴承半径间隙的增大，平均气化强度减小，油膜内气相区域有减小的趋势，气穴效应减弱，其中以轴承半径间隙增大的影响最为明显。
4. 油膜压力场最大压强随转速、偏心率、轴承半径间隙的变化规律与承载力类似，最大压强受供油口面积变化影响较小，随供油压力的升高略有降低。

关键词：船舶柴油机主轴承；润滑特性数值计算；气穴效应；MATLAB；Fluent；

Abstract

The main bearing is one of the most important component of marine diesel engine. The friction power consumption accounts for a large proportion of the total power consumption of the propulsion shafting, Once the lubrication failure occurs, it is easy to lead to dry friction, occurrence of bearing pad burnt, the welding of bearing and shaft, which is harm to the diesel engine and the ship’s navigation safety.

This paper firstly calculates main bearing dimensionless pressure by means of mathematical calculation software MATLAB , and the ship's main bearing lubrication parameters are calculated at the same time .Then explore the effect of eccentricity, ratio of length to diameter ,bearing clearance, viscosity-pressure effect，journal speed on the bearing capacity and friction force, as well as calculate bearing deviation angle in the different bearing eccentricity. Moreover, the grid division software ICEM is used to do the grid work of the main bearing. The model which is completed in the ICEM is imported into CFD numerical simulation software Fluent, focusing on the effect of speed, bearing clearance, eccentricity, the oil port size for pressure on cavitation phenomenon of main bearing. The main results are as follows:

1. The main bearing capacity and the friction force are increasing with the increase of the eccentricity. At the same eccentricity, both of the friction and the bearing capacity are increasing with the increase of the ration of length to diameter. And the main bearing capacity and the friction force are of linear growth with the increase of the journal speed, while the rate of growth is larger with the increase of eccentricity. At the same speed, both of them is increasing with the increase of the eccentricity.
2. The main bearing capacity and friction force decrease rapidly with the increase of the bearing clearance. At the same bearing clearance, both of them is increasing with the increase of eccentricity. When the bearing clearance is less than 0.6mm, the viscosity-pressure effect affects the bearing friction greatly.
3. The research of main bearing cavitation effect shows that with the increase of speed、eccentricity, the average cavitation intensity is increasing, the air phase in the oil film has increased, which enhances cavitation effect. With the increase of oil port area、oil pressure、the bearing clearance , the average cavitation intensity is decreasing ,the air phase in the oil film has decreased, and the increase of bearing clearance is most obvious among the effecting factors.
4. The law between the max pressure of the oil film and the speed、journal clearance、eccentricity is similar with that of bearing capacity. The max pressure has little influence with the oil supply mouth area, and is reduced with the increase of the oil supply pressure.

Key Words：main bearing of marine diesel engine; numerical calculation of lubrication character; cavitation effect; MATLAB; Fluent

目 录

第1章 绪论 1

1.1研究背景与意义 1

1.2国内外研究现状分析 2

1.2.1传统滑动轴承数值计算 2

1.2.2滑动轴承的CFD数值计算软件仿真模拟 3

1.2.3 针对船舶柴油机主轴承的数值计算 4

1.2.4 国外滑动轴承数值计算领域近年来的研究进展 5

1.3本文主要内容及研究方法 5

1.3.1本文主要内容 5

1.3.2本文研究方法 6

第2章 滑动轴承流体动压润滑理论 7

2.1 润滑方式概述 7

2.2 雷诺方程推导 7

2.3 径向滑动轴承几何参数及控制方程 10

2.4 边界条件 11

2.4.1 Sommerfeld边界条件 12

2.4.2 半Sommerfeld边界条件 12

2.4.3 雷诺边界条件 12

2.4.4 质量守恒边界条件 12

2.5 变黏度理论 12

2.6 本章小结 13

第3章 基于MATLAB的船舶柴油机主轴承润滑特性计算 14

3.1求解无量纲雷诺方程 14

3.1.1 编程软件MATLAB概述 14

3.1.2 滑动轴承雷诺方程的无量纲化 14

3.1.3 基于半Sommerfeld边界条件的求解流程 15

3.1.4 无量纲压力分布 17

3.2基于雷诺边界条件与半Sommerfeld边界条件无量纲压力的计算比较 19

3.3 基于MATLAB的船舶柴油机主轴承润滑特性计算 21

3.3.1 船舶柴油机主轴承模型的建立 21

3.3.2不同长径比下主轴承偏心率与偏位角关系研究 22

3.3.3 不同长径比下偏心率与主轴承承载力关系研究 23

3.3.4不同偏心率下轴颈转速与主轴承承载力关系研究 24

3.3.5 不同偏心率下轴承半径间隙与主轴承承载力关系研究 25

3.3.6 不同偏心率下转速与主轴承摩擦力关系研究 26

3.3.7不同长径比下轴承半径间隙与主轴承摩擦力关系研究 27

3.3.8不同长径比下偏心率与主轴承摩擦力关系研究 28

3.4 黏压效应对主轴承摩擦力影响的研究 29

3.5 本章小结 30

第4章 基于Fluent的船舶柴油机主轴承数值仿真模拟 32

4.1 流体仿真软件Fluent概述 32

4.2 CFD计算控制方程简介 32

4.2.1连续性方程 32

4.2.2 N-S方程 33

4.2.3能量方程 33

4.2.4两相流控制方程 34

4.3 网格划分软件ICEM概述 34

4.4 船舶柴油机主轴承几何模型建立及网格划分 35

4.4.1 船舶柴油机主轴承几何模型的建立 35

4.4.2 船舶柴油机主轴承几何模型的六面体结构化网格划分 35

4.5 本章小结 37

第5章 船舶柴油机主轴承Fluent仿真结果分析 38

5.1 气穴效应对主轴承压力场影响分析 38

5.2 转速对主轴承气穴效应的影响研究 41

5.2.1转速对气相体积分数分布情况的影响研究 42

5.2.2 转速对气穴效应影响下压力场分布的影响研究 45

5.3 偏心率对主轴承气穴效应的影响研究 47

5.3.1偏心率对气相体积分数分布情况的影响研究 47

5.3.2 偏心率对气穴效应影响下压力场分布的影响研究 49

5.4 轴承半径间隙对主轴承气穴效应的影响研究 51

5.4.1轴承半径间隙对气相体积分数分布情况的影响研究 52

5.4.2轴承半径间隙对气穴效应影响下压力场分布的影响研究 54