水下轴系—壳体耦合系统振动特性及结构优化分析

发布时间：2018-08-03 06:41

【摘要】：水下航行器在现代国防事业中起到了巨大的作用，而其振动与噪声水平是决定当代水下航行器生命力和隐蔽性攻击能力的最重要的参数之一。水下航行器主要由轴系与壳体两子系统相互耦合而组成，其振动噪声主要来源于三大方面：机械振动噪声、流噪声以及螺旋桨运动引起的振动噪声。其中螺旋桨运动引起的噪声是航行器在多数时间是最主要的振动和噪声源，准确评估并设法降低系统这一原因的振动噪声是实现水下航行器设计与改进的重要环节。螺旋桨运动引起的系统振动包括两部分，分别是螺旋桨直接振动和螺旋桨间接振动，其中引起螺旋桨间接振动有两种主要原因，一是由螺旋桨多方向非定常激励引起的轴系振动经各支撑轴承传递到壳体导致，一是由螺旋桨转动引起轴系与艉轴承之间的摩擦振动传递到壳体导致。针对螺旋桨非定常力激起系统振动及声辐射，论文从轴承支撑角度分析了轴系与壳体接触面的特点及其简化模型，在轴承弹簧阻尼模型的基础上分别建了轴系子系统、空气中轴系-壳体耦合系统和流体中轴系-壳体耦合系统有限元模型，对三种模型进行了固有模态分析，以及纵向、横向激励下系统振动特性分析，并深入研究了三种模型之振动特性变化规律，指出纵向振动是系统振动研究的主要方向；推力轴承基座结构对纵向振动传递有着重要影响。除此之外，论文还从表面声压、辐射声压、声辐射功率及声辐射效率等方面探究系统的基本声辐射特性，研究了其与系统振动特性的关系，指出了系统纵向振动引起的声辐射对系统总体声辐射的重要作用。以往的研究都认为螺旋桨非定常激励是系统主要外激励，然而实际系统中由于艉轴承与轴系摩擦引起的振动与噪声对系统特性同样有影响。对于轴系与艉轴承摩擦振动，文章首先分析了水润滑橡胶艉轴承的摩擦特性，并利用模态减缩研究了艉轴承摩擦激励产生的自激振荡及粘-滑现象。结果表明，摩擦振荡的产生是由系统纵向振动-横向振动-摩擦振动相互耦合而导致的自振失稳的结果；模态阻尼、轴系转速、支撑刚度等诸多因素都可以影响摩擦振荡的形成。此外，文章针对轴系完全对中和轴系有不对中的两种不同工况，分别讨论了摩擦振动的特点，并将摩擦振动与螺旋桨非定常激励对整体振动的影响程度进行了分析，得出系统在轴系对中条件不良时，摩擦振动是不可忽略的振动源的结论。基于振动及噪声特性的分析，文章提出了改变轴承刚度及阻尼参数、添加纵向加强筋、改变推力轴承基座结构、添加纵向隔振器、艉部下移等方案控制系统振动，，讨论了每种措施的效果与可行性。对比结果表明，若要求对结构改动较小，通过添加纵向隔振器及添加一根加强筋等方式能够起到一定的减振效果；若从设计阶段改进，应用对称式主推力轴承基座支撑，不仅可以减小系统在纵向及横向激励下的振动响应，还可以减小系统的纵-横耦合程度。本文有关结构优化分析的研究对工程设计具有一定的借鉴意义。
[Abstract]:Underwater vehicle plays a great role in modern national defense, and its vibration and noise level is one of the most important parameters to determine the vitality of the contemporary underwater vehicle and the ability of concealed attack. The underwater vehicle is mainly composed of the coupling of the shafting and the shell two subsystems, and its vibration and noise are mainly derived from three aspects. Mechanical vibration noise, flow noise and the vibration noise caused by the propeller motion. The noise caused by the propeller motion is the most important vibration and noise source of the aircraft in most of the time. It is an important link to realize the design and improvement of the underwater navigator by accurate assessment and reduction of the vibration and noise of the system. The vibration caused by the motion consists of two parts, which are the direct vibration of the propeller and the indirect vibration of the propeller, in which there are two main reasons for the indirect vibration of the propeller. One is that the shaft vibration caused by the unsteady excitation of the propeller is transmitted to the shell by the bearing of the propeller, and the other is the shaft and the stern shaft caused by the rotation of the propeller. The friction vibration between the bearings is transmitted to the shell.
Aiming at the unsteady force of the propeller to arouse the vibration and sound radiation of the system, the characteristics and simplified model of the contact surface of the shafting and the shell are analyzed from the bearing support angle. On the basis of the bearing spring damping model, the shafting subsystem, the axle housing coupling system in the air and the finite element model of the shaft shell coupling system in the fluid are built respectively. The inherent modal analysis of the three models and the analysis of the vibration characteristics of the system under the longitudinal and transverse excitation are carried out, and the variation of the vibration characteristics of the three models is deeply studied. It is pointed out that the longitudinal vibration is the main direction of the study of the system vibration, and the thrust bearing base structure has an important influence on the longitudinal vibration transmission. The basic sound radiation characteristics of the system are investigated from the surface acoustic pressure, the radiation pressure, the sound radiation power and the sound radiation efficiency. The relationship between the system and the vibration characteristics of the system is studied. The important role of the sound radiation caused by the longitudinal vibration of the system to the overall sound radiation of the system is pointed out.
The previous research holds that the unsteady propeller excitation is the main external excitation of the system. However, the vibration and noise caused by the friction between the stern bearing and the shaft system have the same influence on the system characteristics. The self excited oscillation and stick slip phenomenon of the stern bearing friction excitation are studied. The results show that the generation of the friction oscillation is the result of the self vibration instability caused by the coupling between the longitudinal vibration of the system - the transverse vibration and the friction vibration of the system; and the modal damping, the shaft speed, the support stiffness and so on can affect the formation of the friction oscillation. In this paper, the characteristics of friction vibration are discussed respectively for the two different working conditions of the shaft system with the neutral axis. The influence degree of the friction vibration and the propeller unsteady excitation on the whole vibration is analyzed. The conclusion is that the friction vibration is an unnegligible source of vibration when the system is poor in the shaft system.
Based on the analysis of the vibration and noise characteristics, the effect and feasibility of the control system are discussed, including the change of the bearing stiffness and damping parameters, the addition of the longitudinal reinforcement, the change of the thrust bearing base structure, the addition of the longitudinal vibration isolator, the stern shift and so on. In the design phase, the vibration response of the system can be reduced and the longitudinal and transverse coupling of the system can be reduced. The study of analysis has certain reference significance for engineering design.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TJ6;TB123

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