【作者】 孙艳红；

【导师】 丁千；

【作者基本信息】 天津大学 ， 一般力学与力学基础， 2004， 硕士

【摘要】 叶片事故的统计分析表明,叶片损坏大多数是由于叶片振动产生的动应力过大所致。为了降低叶片的振动应力,汽轮机厂家越来越多地采用带有阻尼围带或凸肩的叶片结构,即阻尼叶片。阻尼叶片通过围带或凸肩间的相互干摩擦来消耗叶片能量,起到减振的作用。本文对干摩擦阻尼叶片多谐波激振响应进行分析研究,主要工作分为以下几个方面:第一部分:叶片阻尼机理和激振力的介绍分析介绍分析了各种阻尼产生的机理,以及相应的模型,特别是对界面摩擦阻尼的机理及其数学模型进行了较为详细的探讨。对摩擦面间正压力变化时摩擦力进行分析。激振力研究是阻尼叶片动力特性研究的一个重要组成部分。在激振力的各阶谐波分量中,影响叶片安全运行的激振力仅是接近叶片自振频率的分量,本文考虑第一阶、第二阶和第Z阶谐波分量对叶片动力特性的影响。第二部分:叶片单自由度和两自由度模型分析首先,建立叶片单自由度模型,利用平均法求解叶片的运动方程,研究一阶和二阶主共振情况下幅频响应曲线,分析各个主要系统参数对频响曲线的影响规律。然后,考虑弯曲和扭转耦合情况下的叶片模型,建立两自由度的叶片运动方程,应用谐波平衡法得出运动方程的周期解,分析一、二阶主共振情况下系统参数对频响曲线的影响,并与数值解进行比较验证解析解的准确性。最后对全文进行总结。本文研究得出,增加叶片的界面摩擦阻尼是一种非常有效的叶片减振方法。由于界面干摩擦的介入,使得阻尼叶片具有非线性的动力特性。与线性动力系统不同,阻尼叶片的频率不再是它的固有特性,其频率受外界激振力的影响。本文对阻尼器接触端正压力、汽流激振力、摩擦界面的剪切刚度、摩擦系数等参数对叶片动力特性的影响进行了理论、计算和设计应用的研究。更多还原

【Abstract】 One of the common structural failure of blades is due to excessive stresses caused by large amplitude vibrations. To reduce the vibratory stress of blades, the damped blades with integral wire or shroud are widely used by turbine works. As the vibratory energy is dissipated by the dry friction between the dampers, the vibration of blades is reduced. The dynamic characteristics of the dry friction damped blades influenced by the multi-harmonic excitations will be discussed in this paper. Part one, introduction and analysis of the damped mechanism and the excitation force of turbine blades.The mechanism and corresponding models, especially the interface friction, of many kinds of dampers are introduced and analyzed. The analytical friction force model with variation of normal pressure between friction surfaces will be considered in the following analysis. The excitation force is one of the most important elements for research of dynamic characteristics of damped blades. Among various-order harmonics, the harmonic component, which approaches the natural-frequency of blade, can have the main influence on the safety of the blades. The first, second and Z-order harmonics are considered in this paper to analyze the dynamics of blades.Part two, dynamics of the one- and two-dof models. Firstly, the one-dof blade model is studied by the average method. The average equations are determined, and the amplitude-frequency curves in the first and second-order resonances are presented. The influences of the system parameters on the amplitude- frequency curves are discussed. Secondly, taking into account the coupling of flexion-torsion, the two-dof blade model is studied by the harmonic balance method to obtain the response equations. The influences of the system parameters on the amplitude- frequency curves of the first and second-order resonances are discussed. Numerical solutions are used to prove the accuracy of the analytical analyses. The results in this paper show that the dry friction in blades plays a very important role in reducing vibration amplitude of the blades. The normal force between the rubbing surfaces can influence the damping effect of blades. Through the study we found that there is an optimum value for the normal force, under which the vibration of blades can be damped effectively. The damped blades is a nonlinear dynamic system, so its natural frequency can be influenced by external force. Besides, the influence of shear stiffness of rubbing surfaces, the place of the damper on the blades, and the friction coefficient on dynamic characteristics of blades are also discussed.更多还原