轴承标高对多跨转子-轴承系统非线性稳定性的影响研究

建立了考虑转子-轴承标高与非线性油膜力的多跨转子-轴承系统高维非线性动力学模型。利用固定界面模态综合法对该模型进行降维,采用Newmark逐步积分法对降维后的动力学模型进行数值计算,可得到转子在各种标高情况下发生油膜失稳的转速门槛值和轴承标高变化对系统动力稳定性的影响规律。对200MW汽轮发电机组转子-轴承系统计算分析表明：由于低压转子后轴承的标高抬起,将导致发电机转子前轴承轴颈的失稳转速显著提前,系统的稳定性降低。分析结果从理论上解释了电站200MW汽轮发电机组发电机前轴承处转子易发生油膜失稳的原因,并且证明了本文所提出方法的有效性。     

基于有限单元和模型降阶的储能飞轮转子动力学建模及分析

针对使用Jeffcott转子模型的集中质量法建立飞轮转子-轴承系统动力学模型时将转子段视为集中质量点,未考虑转子轮盘厚度的问题,提出一种基于有限单元法和模型降阶法的飞轮转子-轴承系统建模方法.以飞轮转子-电机转子-轴承系统为对象,基于此建模方法进行动特性计算,求解飞轮转子在不同轮盘厚度下的固有频率,并与Jeffcott...     

立式转子-轴承系统动力学特性研究

建立了立式转子-轴承系统的动力学模型,采用Newmark数值方法研究了不平衡量及轴承参数对立式转子-轴承系统的动力学特性和稳定性影响并与卧式转子系统进行了对比分析.结果表明:和卧式转子相比,立式转子由于载荷轻稳定性差,稳定性对参数的改变也更为敏感.通过改造Bently-RK4转子-轴承系统实验台,试验验证了上述立式转子与卧式转子的动力学特性差别.研究结果对于立式转子-轴承系统的设计和故障诊断具有一定的参考价值.     

汽轮机自带冠叶片接触碰撞系统的谐波平衡解

针对汽轮机自带冠叶片的接触减振机理问题,考虑惯性力和气流激振力对叶片振动的影响,采用Hertz接触力模型和悬臂梁振动理论建立了自带冠叶片接触碰撞的动力学模型.利用Galerkin模态截断方法,截取系统第一阶模态,实现对悬臂梁系统的降维处理.对降维后的系统,采用谐波平衡法分别获得了系统在有阻尼和无阻尼情况下的解析解.所得结果为自带冠叶片接触碰撞问题的进一步研究提供了理论依据.     

基于Galerkin法的汽轮机转子热应力在线计算模型

导出一种在线监测汽轮机转子热应力的计算模型.首先采用Galerkin有限元法,导出转子瞬态温度场,再根据温度场结果计算转子热应力.仿真试验表明:该模型计算速度快,计算精度高.并且这种二维离散模型,可以进一步用来计算转子的轴向热胀差.同时,该模型还可用于其它具有类似边界条件的二维轴对称体的工程实际换热问题,如燃气轮机、发电机转子等.     

轴承-转子系统稳定性实验研究

研究了圆轴承非线性油膜力支承下转子系统动力学特性及稳定性,以及不平衡量及轴承参数对稳定性影响规律.结果显示,适当增大转子不平衡量、减小轴承长径比、降低润滑油黏度、减小轴承间隙会提高转子-轴承系统稳定性.对圆轴承支承下转子-轴承系统动力学特性进行了实验研究,给出了系统油膜失稳规律,验证了理论分析结果,同时验证了提出的模型正确.研究结果为油膜失稳故障预测及防范提供参考.     

转子-轴承系统小裂纹识别的HHT谱分析方法

针对低转速工况下转子-轴承系统小裂纹识别难的问题,提出Hilbert-Huang变换谱和边际谱分析的方法。分别建立刚性支承及轴承支承的裂纹转子模型,比较二者频谱差异,并采用四阶Runge-Kutta法求解重力占优背景下裂纹转子-轴承系统动力学方程;对时域信号进行经验模态分解,提取其IMF分量,计算各IMF分量的HHT谱及边际谱,并对无裂纹和小裂纹情况进行分析。结果表明,对于受非线性油膜力影响的裂纹转子-轴承系统,HHT方法能够很好体现裂纹刚度随时间变化的过程;通过EMD方法分解出的IMF分量,在小裂纹、低转速下对裂纹的变化有很好的敏感性,能有效识别转子-轴承系统的小裂纹故障。     

不同油膜力模型下转子椭圆轴承系统的动力学分析

1引言滑动轴承的非线性油膜力模型是转子-轴承系统非线性动力学分析和研究的关键问题。滑动轴承的油膜力具有强烈的非线性特性,研究转子-椭圆轴承系统的非线性动力学问题关键在于获得椭圆轴承的油膜力模型。其中椭圆轴承的非线性油膜力的计算精度和计算速度将直接影响到转子-轴     

某重型燃气轮机临界转速计算方法研究

提出了适用于拉杆形式重型燃气轮机组转子动力学计算的一维模型简化方法。基于ANSYS的梁单元,建立了某重型燃气轮机转子的一维有限元模型,模型中考虑了接触效应对转子刚度的影响,并对该转子轴承系统临界转速进行了计算分析。还采用了二维广义轴对称单元模型进行了相关计算,作为对一维简化方法的验证。最后,进行了重型燃机整机现场振动数据采集,取得了临界转速的实验值,有限元计算结果与实验值吻合程度良好。     

标高对转子-滑动轴承系统动力学特性影响研究

通过理论和实验研究了多跨转子-轴承系统标高对其轴承载荷分配、临界转速及稳定性的影响规律.结果显示,轴承标高变化对柔性转子临界转速影响较小,但对轴系稳定性有较大影响.研究结论为多跨轴系标高设计及现场调试提供依据.     

Numerical analysis of fluid flow due to mixed convection in a lid-driven cavity having a heated circular hollow cylinder

Mixed convection heat transfer in a lid-driven cavity along with a heated circular hollow cylinder positioned at the center of the cavity has been analyzed numerically. The present study simulates a realistic system such as air-cooled electronic equipment with a heat component or an oven with heater. A Galerkin weighted residual finite element method with a Newton–Raphson iterative algorithm is adopted to solve the governing equations. The computation is carried out for wide ranges of the Richardson numbers, cylinder diameter and solid fluid thermal conductivity ratio. Results are presented in the form of streamlines, isothermal lines, average Nusselt number at the heated surface and fluid temperature in the cavity for the mentioned parameters. It is found that the flow field and temperature distribution strongly depend on the cylinder diameter and also the solid–fluid thermal conductivity ratio at the three convective regimes.     

Parabolic Heat Conduction Specialized Applications Involving Imperfect Contact Surfaces: Local Discontinuous Galerkin Finite Element Method—Part 2

Parabolic heat conduction specialized applications involving imperfect thermal contact surfaces are analyzed via the Local Discontinuous Galerkin (LDG) finite element method. In this paper, we describe the advantages of the LDG finite element formulation over the traditional continuous Galerkin (CG) finite element method for modeling imperfect thermal contact between surfaces. To-date, mostly interface/gap elements have been primarily used to model the imperfect contact between two surfaces to solve thermal contact resistance problems. The LDG method eliminates the use of such interface/gap elements and provides a higher degree of accuracy. Several illustrative 2-D applications highlight the effectiveness of the present LDG finite element formulations for this class of problems.     

基于复合材料薄壁结构的转子叶片非线性气弹时域响应分析

阐述了基于复合材料薄壁梁结构的风力机转子叶片非线性气弹响应分析方法。结构是基于不同刚度系数的挥舞和扭转组成的弯-扭耦合模型,而非线性气动力的计算采用非线性ONERA模型。在Galerkin法基础上,利用片条理论分解了非线性气动力的积分项,构建了结构和气动力相结合的非线性微分方程组,给出了分析非线性气弹响应的方法,并基于小范围近似法进行了线性化,研究了线性化后的时域响应,给出了基于线性化后的时域响应进行稳定性分析的方法。     

Meshless method based on the local weak-forms for steady-state heat conduction problems

In this article, the meshless local Petrov–Galerkin (MLPG) method is applied to compute two steady-state heat conduction problems of irregular complex domain in 2D space. The essential boundary condition is enforced by the transformation method, and the MLS method is used for interpolation schemes. A numerical example that has analytical solution shows the present method can obtain desired accuracy and efficiency. Two cases in engineering with irregular boundary are computed to validate the approach by comparing the present method with the finite volume method (FVM) solutions obtained from a commercial CFD package FLUENT 6.3. The results show that the present method is in good agreement with FVM. It is expected that MLPG method (which is a truly meshless) is very promising in solving engineering heat conduction problems within irregular domains.     

Solving heat transfer problems with phase change via smoothed effective heat capacity and element-free Galerkin methods

This paper presents a smoothed effective heat capacity model that is combined with element-free Galerkin (EFG) method, to solve heat transfer problems with phase change. The Sigmoid function is employed to build a continuous and smooth effective heat capacity function, so as to avoid possible error caused by the step-jump. The proposed numerical model is verified via numerical examples, and the effects of arrangement of EFG nodes and parameters relevant with Sigmoid function on the solutions are investigated. Satisfactory results are achieved in comparison with analytical solutions.     

基于本征正交分解的无叶扩压器流动稳定性Galerkin降阶模型

将分析湍流拟序结构中的本征正交分解技术运用到离心压气机无叶扩压器的流动稳定性分析中,并将其与Galerkin投影法相结合建立了无叶扩压器内部流场的降阶模型。使用本征正交分解技术提取无叶扩压器在某来流入口角下非定常流场的主要流动模态,将流动控制方程通过Galerkin方法投影至由有限阶本征正交模态所组成的空间上,得到无叶扩压器流动稳定性降阶模型。计算结果表明:该模型可用于判断不同来流入口角下的扩压器流动稳定性,并将降阶模型的计算结果与流场数值模拟结果和线性稳定性预测结果进行对比,验证了此降阶方法的合理性。     

On the Representations of Solutions of the Theory of Thermoelasticity with Microtemperatures

In the present paper the linear theory of thermoelasticity with microtemperatures is considered. First, the representation of Galerkin type solution of equations of motion is obtained. Then, the representation theorem of Galerkin type of the system of equations of steady oscillations (vibrations) is presented. Finally, the general solution of the system of homogeneous equations of steady oscillations in terms of nine metaharmonic functions is established.     

A numerical study on the effect of a heated hollow cylinder on mixed convection in a ventilated cavity

The present work is aimed to study mixed convection heat transfer characteristics within a ventilated square cavity having a heated hollow cylinder. The heated hollow cylinder is placed at the center of the cavity. In addition, the wall of the cavity is assumed to be adiabatic. Flows are imposed through the inlet at the bottom of the left wall and exited at the top of the right wall of the cavity. The present study simulates a practical system such as air-cooled electronic equipment with a heat component or an oven with heater. Emphasis is sited on the influences of the cylinder diameter and the thermal conductivity of the cylinder in the cavity. The consequent mathematical model is governed by the coupled equations of mass, momentum and energy and solved by employing Galerkin weighted residual method of finite element formulation. A wide range of pertinent parameters such as Reynolds number, Richardson number, cylinder diameter and the solid-fluid thermal conductivity ratio are considered in the present study. Various results such as the streamlines, isotherms, heat transfer rates in terms of the average Nusselt number and average fluid temperature in the cavity are presented for different aforesaid parameters. It is observed that the cylinder diameter has significant effect on both the flow and thermal fields but the solid-fluid thermal conductivity ratio has significant effect only on the thermal field.     

Discontinuous Galerkin Finite Element Methods for Numerical Simulations of Thermoelasticity

In this article, the discontinuous Galerkin (DG) finite element methods are extended to numerical simulations of uncoupling thermoelasticity. A thermoelastic formulation of interior penalty DG (IP-DG) method is presented and aspects of the numerical implementation are discussed in matrix form. The feasibility of the method for general thermoelastic simulations is validated through some typical test cases. Investigations are performed in which the method is applied to problems with thermal stress discontinuities induced by non-homogeneous inclusions, illustrating that reasonably ranged magnitude of IP term can well deal with the problems, and IP parameter increasing can effectively suppress the non-physical oscillations around discontinuities although its excess may affect solution accuracy in smooth region to some extent.     

Online balancing of the rotor-bearing unit of the flywheel energy storage system

采用SB-7700型动平衡仪对400 kW/10 MJ飞轮储能系统轴系进行了本机动平衡,依据动平衡结果,提出了增加平衡工艺飞轮的修改设计.采用两平面方法进行本机动平衡后,飞轮储能机组达到额定3600 r/min的高速稳定运行.振动测试表明,充电,放电状态振动特性有所差别,放电功率对共振区振动幅频特性有显著影响,这反映了永磁电机电磁力对同步振动的作用.