曲轴主轴承油膜动力润滑与系统动力学的耦合分析

在分析内燃机活塞-连杆-曲轴系统的系统动力学行为和曲轴主轴承的流体动压润滑基础上，建立了该系统的系统动力学与流体动力润滑耦合作用下的动力学分析模型，并提出了求解此模型的数值解法，利用机械系统动力学分析软件ADAMS的求解器（Solver）和自己编写的计算流体动力润滑程序连接调用进行了系统动力学与流体动力润滑的耦合分析。通过比较不考虑油膜动力润滑时缸体各部分的动态受力和考虑油膜动力润滑后缸体的动态受力表明：润滑油膜的动力耦合具有使缸体各部位受力趋于均匀化的作用，以下不考虑油膜动力耦合作用的零部件最大受力作为设计依据的零部件设计具有过大的安全裕度，在内燃机零部件设计时考虑摩擦学与系统动力学的耦合是非常必要的。     

悬臂转子系统振动特性分析

推导建立了考虑转轮叶片作用的悬臂转子系统动力学方程.对运动微分方程进行数值积分,分析了质量偏心、转轮叶片质量及轴承之间的距离等对悬臂转子系统振动特性的影响.数值分析结果表明,随着圆盘2质量偏心的不断增加,转子系统的径向位移近似线性增大;当转轮叶片质量、轴承之间的距离等取不同值时,转子系统径向位移的变化情况较为复杂.圆盘1的径向位移值可能会大于、等于或小于圆盘2的径向位移值.     

横向流体激振力作用下叶轮转子的分岔特性

将离心叶轮转子系统简化为Jeffcott转子,建立了带有支座松动与碰摩耦合故障的不平衡离心叶轮转子在非线性横向流体激振力和非线性轴承油膜力作用下的振动分析模型,并推导了系统的无量纲运动方程.运用数值积分法研究了系统的分岔特性,最后分析了横向流体激振力对含有松动与碰摩的离心叶轮转子系统动力学性能的影响.结果表明:在转速较高时,横向流体激振力对该类转子的分岔特性有较大影响.     

风力机旋转叶片动力学方程的Neumann级数解法

运用现代柔性多体动力学方法,研究了水平轴风力机柔性叶片空间旋转运动与其弹性变形间的相互耦合关系及其所导致的动力学效应;导出了旋转叶片的有限元动力学方程及其数值求解方法;对大型风力机叶片在机械和气动载荷作用下的弯曲变形进行了动态模拟。由于该有限元动力学方程为时变方程,文中应用Neumann级数和Newmark直接积分方法求解动力方程,编制了相应的计算机程序;以1.5MW风力机叶片为例,计算了风力机在启动、刹车和正常运转时的叶片弯曲挠度响应,并与常规有限元数值分析结果进行了比较。结果表明,该方法能有效地求解该类时变方程并准确地反映旋转叶片的动力学特性和动力学响应,本文工作为进一步进行叶片强度和气动弹性稳定性分析打下了基础。     

外激励作用下不平衡转子系统弯扭耦合非线性振动特性研究

采用Lagrange方程考虑6个方向的自由度,推导了考虑弯扭耦合振动的转子系统运动方程。分析了两种不平衡的作用,即静不平衡和动不平衡,同时考虑了重力和陀螺效应的影响。当外激励力和外激励力矩作用在该系统上时,采用数值仿真研究了系统弯扭耦合的非线性振动特性,发现系统所具有的各种非线性振动现象。对于建立比较完备的转子弯扭耦合振动模型和转子系统的故障诊断具有一定的意义。     

Muszynska模型经验系数对转子系统稳定性的影响

基于Muszynska模型,推导建立密封流体激振力作用下的转子一密封系统非线性动力学方程.对运动微分方程进行数值分析,研究了该系统的分岔特性以及Muszynska模型中经验系数对系统稳定性的影响规律.分析结果表明,密封流体激振力导致的转子非线性动力学行为具有非常复杂的演化过程,其中平均周向速比常数及描述平均周向速比与转子涡动之间关系的经验系数是影响转子系统稳定性的关键因素,而其它经验系数影响均在5%以内,该结果为降低相关的实验费用提供了理论依据.     

流体机械中浸液转子动力学特性的研究

基于大间隙环流中转子运动的理论模型,应用数值方法研究了流体机械中浸在大间隙环流中偏心转子的动力学特性。研究结果表明：惯性耦合动力学效应已不可忽略;偏心率,转子转速和壁面粗糙度等参数是影响大间隙环流中偏心转子动力学特性的重要参数。图4参4     

连续转子轴承系统的非线性动力学行为研究

对一转子轴承系统,采用有限元方法建立了非线性连续转子轴承系统模型,分别采用直接积分法和模态综合法对偏心情况下转子的非线性动力学行为进行了分析,并对两种方法的结果进行比较发现,直接积分法对于求解非线性振动问题更有效。运用简单离散方法对该转子轴承系统进行了分析,其结果与有限元法偏差较大。有限元的分析结果表明,该转子轴承系统的动力学响应为一典型的油膜震荡过程,其非线性动力学运动形式为HOpf分叉。     

水平轴风轮机偏转动态特性的数值计算分析研究

本文建立了准定常流场中具有任意桨叶数的半刚笥桨叶转子模型，用修正偏斜尾流的叶素／动量理论，推导出转子的偏转运动方程，并考虑了机构的偏转阻尼和摩擦、水平及垂直风切变、塔景的影响。在线性和幂次律曲线风廓线、随时间变化的风速、风向等条件下，在时域里数值方法求解转子的运动方程并编制了计算机程序。     

两种裂纹转子模型的稳定性分析

在分析现有模型局限性的基础上,考虑转子在临界转速附近复杂的涡动状态,基于涡动角构建了含横向裂纹的Jeffcott转子的动力学模型.运用Floquet稳定性理论分析了基于涡动角和基于自转角这两种裂纹转子模型运动的稳定性.结果表明:系统参数对两者的运动稳定性都有较大影响.前者只在临界转速附近存在失稳区,后者在临界转速和三分之二临界转速附近都存在失稳区.通过数值计算结果以及理论分析的对比,发现基于涡动角的裂纹转子动力学模型更具普适性.     

Aerodynamic analysis of HAWTs operating in unsteady conditions

This article presents a numerical method for predicting unsteady aerodynamics of horizontal axis wind turbines (HAWTs). In this method the flow field is described by the unsteady incompressible Navier–Stokes equations. The rotor and tower are idealized respectively as actuator disc and flat plate permeable surfaces on which external normal surficial forces are balanced by fluid pressure discontinuities. The external forces exerted by the rotor and tower on the flow are prescribed according to blade element theory. Dynamic behaviour of the rotor aerodynamic characteristics is simulated using either the Gormont or the Beddoes–Leishman model. The resulting mathematical formulation is solved using a control volume finite element method. The fully implicit scheme is used for time discretization. In general, the proposed method has demonstrated its capability to adequately represent the field data. It has been demonstrated that the accuracy of the predicted results depends primarily on the dynamic stall model as well as on the turbulence model employed. Copyright © 2001 John Wiley & Sons, Ltd.     

A Finite Element based State Model of Solid Rotor Synchronous Machines

In this work, a state model which portrays the dynamic electromagnetic characteristics of a synchronous machine is derived based upon the first order finite element method. The method of finite elements is used to determine the axial component of magnetic vector potential throughout the cross section of the machine. Algebraic relationships between the winding voltages and the magnetic vector potentials are derived. These are used to establish a state model which admits winding voltages as inputs. The resulting model consists of a set of first order, ordinary differential equations which predict vector potentials at grid nodes along with the winding currents as time proceeds following arbitrary disturbances in stator or rotor voltages. As an initial verification step, this method has been applied in two linear examples. The first involves a simplified geometric representation of the synchronous machine for which an analytical solution of the defining field equations can be obtained. The second involves a more detailed geometry which includes stator and rotor slots. Numerical solutions are shown to be in excellent agreement with analytical solutions for the simplified structure. In the detailed geometry, numerical solutions are shown to compare favorably with the classical equivalent circuit representation.     

考虑陀螺效应的增压器转子动力特性分析

借鉴对称矩阵的子空间迭代法思想,将辛子空间迭代法应用于增压器系统,以某增压器转子为例,充分考虑涡轮增压器的特殊性,建立了涡轮增压器转子的有限元模型,并在计算模型中综合考虑了轮盘的陀螺力矩,转动惯量、支承和轴套等因素,分别计算了增压器转子在不同支承刚度下临界转速、振型的变化趋势,分析了支承刚度对增压器转子动力学特性的影响.计算结果表明:改变支承刚度可以有效地调整该增压器转子的临界转速,但对转子各阶临界转速振型影响不大.     

Numerical Modelling of the Aeroelastic Behaviour and Variable Loads for the Turbine Stage in 3D Transonic Flow

Introduction Aeroelastic phenomena in the turbine stage are characterized by instability, continuous interaction and energy exchange between the fluid and the structure; so they cannot be studied properly in the frame of each of uncoupled domains separately (aerodynamics or structural dynamics). The traditional approach in flutter calculations of bladed disks is based on frequency domain analysis[1,2], in which the blade motion is assumed to be a harmonic function of time with a constant phas…     

Effect of wind turbine surge motion on rotor thrust and induced velocity

Offshore wind turbines on floating platforms will experience larger motions than comparable bottom fixed wind turbines—for which the majority of industry standard design codes have been developed and validated. In this paper, the effect of a periodic surge motion on the integrated loads and induced velocity on a wind turbine rotor is investigated. Specifically, the performance of blade element momentum theory with a quasisteady wake as well as two widely used engineering dynamic inflow models is evaluated. A moving actuator disc model is used as reference, since the dynamics associated with the wake will be inherently included in the solution of the associated fluid dynamic problem. Through analysis of integrated rotor loads, induced velocities and aerodynamic damping, it is concluded that typical surge motions are sufficiently slow to not affect the wake dynamics predicted by engineering models significantly. Copyright © 2012 John Wiley & Sons, Ltd.     

Numerical investigation of airflow through a Savonius rotor

The aim of this report is to present a model of a rigid‐rotor system based on computational fluid dynamics (CFD), which is applied on a vertical axis wind turbine (VAWT) research. Its originality results from the use of the average value of the variable rotational speed method taken in a periodic steady‐state (PSS) of the VAWT rotor instead of the classical fixed rotational speed method. This approach was chosen in order to determine the mechanical and aerodynamic parameters of the wind turbine. The modeling method uses an implicit Euler iterative solution strategy, which resolves the coupling between fixed and moving rotor domains. The main methods that were adopted are based on the three‐dimensional modeling of the interaction of the fluid flow with a rigid‐rotor. The strategy consists of using the Reynolds averaged Navier Stokes (RANS) equations with the standard k‐ ? and SST k‐ ω models to solve the fluid flow problem. To perform the rigid‐rotor motion in a fluid, the one degree of freedom (1‐DOF) method was applied. In the present study, the steady‐state and dynamic CFD simulations of the Savonius rotor are adopted to contribute to the validation elements of the VAWT models that are used. The dynamic study allows the investigation of the rotor behavior and the relation between velocity, pressure, and vorticity fields in and around the rotor blades. The flow fields generated by the rotation of the Savonius rotor were investigated in the half revolution period of the rotor angle θ from 0° to 180°. In this range of θ, the focus is on generating and dissipating vortices. Copyright © 2013 John Wiley & Sons, Ltd.     

600 MW汽轮发电机组轴系非线性动力学响应分析

采用等参元有限元法建立了国产600MW汽轮发电机组轴系的非线性动力学模型,利用有限元分析程序ADINA对某国产600MW汽轮发电机组轴系的非线性动力学-向应进行了分析和计算。在计算中通过ADINA程序提供的用户接口,考虑了滑动轴承的非线性油膜力,并与线性动力学分析计算结果进行了比较,计算结果表明,利用ADINA程序结合非线性动力学理论对大型实际机组轴系进行非线性动力学分析和计算是必要的和可行的。从而为大型实际机组轴系进行非线性动力学稳定性分析和优化设计提供了依据。     

Dynamic behaviour of methane heat exchange reformer for residential fuel cell power generation system

Due to its heat integration utility, heat exchange reformer (HER) is suitable to use for PEMFC-based residential power generation system. Since dynamics response of reformer affects overall dynamics of fuel processing system, response of HER with step change in various input parameters also needs to be studied. In this study, we present an improved distributed dynamic model for HER which is capable of computing load following characteristics. The dynamic model consists of 20 partial differential equations which are discritized using spline collocation on finite elements. Resulting differential equations along with boundary conditions are solved by stiff solver which utilizes variable order method based on numerical differentiation formulae. Step variations in various input parameters are considered and dynamic response of HER is simulated at those variations. The results provide valuable information about dynamic nature of HER which can be used to frame suitable control strategy.