汽轮机轴封-转子系统动力学特性的数值分析

建立了汽轮机轴封-转子系统中蒸汽流动作用在转子上的8个蒸汽气动力等效动特性系数计算方程.基于振荡流体力学原理,计入了水蒸汽热物性变化的影响.针对某百万等级超超临界机组高压平衡活塞轴封,分别计算了设计工况下蒸汽在轴封中流动时轴封内温度、压力和剪切应力分布,得到了蒸汽气动力作用在转子上的8个等效动特性系数,计算结果与国外计算程序结果较为吻合.计算分析表明:高压平衡活塞轴封处蒸汽气动力对转子临界转速的影响比较明显,水平和垂直复模态临界转速涨幅分别达10%和4.4%.     

突变偏心距激励下两级离心泵转子系统动力学分析

为分析两级离心泵叶轮偏心距激励突变时转子系统产生振动和冲击的机理,改进了将质量集中于叶轮的方法并建立了悬臂式两级离心泵转子系统动力学方程,得到了2个叶轮在不同方向振动量的无量纲化解析式,提出了无量纲化的偏心距效应系数,以判别不同叶轮偏心距激励突变对整个转子系统振动的影响,最后对叶轮偏心距激励突变时其弯曲振动特性和几何中心位移规律进行了分析.结果 表明:与叶轮1偏心距激励突变相比,叶轮2偏心距激励突变对离心泵的影响更大;叶轮2偏心距激励突变对叶轮1的影响大于叶轮1偏心距激励突变对叶轮2的影响;相比偏心距激励突减,偏心距激励突增时超调量更大、对系统破坏性更强.     

水轮发电机转子典型机电故障的不平衡磁拉力研究

针对水轮发电机发生转子偏心和转子绕组匝间短路故障产生不平衡磁拉力,进而引起机组强烈振动的情况,通过有限元仿真软件建立一台550MW水轮发电机二维仿真模型,分别对转子动、静偏心故障及转子绕组匝间短路故障进行模拟,计算各故障情况下的不平衡磁拉力,分析转子偏心程度、方向和转子绕组匝间短路程度对不平衡磁拉力大小和方向的影响。结果表明,不论是发生转子偏心故障还是发生转子绕组匝间短路故障,不平衡磁拉力数值均随故障程度的加重而增大,且不平衡磁拉力方向为诊断转子偏心方向和空载情况下匝间短路故障磁极提供帮助。研究成果为未来研究水轮发电机振动现象和故障检测奠定了基础。     

迷宫汽封振动频率对转子动特性系数的影响

对迷宫汽封转子振动频率对转子动特性系数的影响进行了分析。通过对定常流场和非定常流场的求解，最终可以得到各动特性系数。分析结果表明：振动频率对转子动力特性系数的影响是显著的，并且随着振动频率的增大，转子的稳定性先提高后降低。     

200MW汽轮机低压转子-轴承系统的非线性动力学分析

采用数值计算方法对实际大型转子-轴承系统的非线性动力学特性进行了研究，计算结果能与现场的运行经验很好地吻合。用有限元法建立了200Mw汽轮机低压转子-轴承系统的非线性振动微分方程。采用Newmark逐步积分法对转子在升、降速过程中的振动响应进行了数值仿真，得到了转子发生油膜失稳的转速和油膜振荡的“惯性迟滞”现象。对转子的重力和不平衡量对系统的油膜涡动和油膜振荡的影响进行了计算和分析。计算得到了转子的振动随转子的偏心距、轴承的长径比、间隙比、润滑油粘度的变化规律，分析结果为定量和定性分析该类机组转子-轴承系统的稳定性提供了参考依据。图15表1参7     

迷宫轴封气流周向剪切力对转子动态特性系数的影响

采用扰动法计算分析了透平机械直齿型轴封中非定常高压气流流动对涡动转子的气流激振问题,针对进口速度、进口压力、转子转速、涡动频率以及间隙大小对转子动特性系数的影响进行了详尽计算.结果表明,表面周向剪切力对转子动特性系数的影响不可忽略.     

偏心方形管内超临界水传热特性数值研究

采用SSG湍流模型,对偏心方管内超临界水传热特性进行三维数值研究。研究了不同偏心距对通道内传热特性的影响及通道内的周向传热不均匀特性。研究结果表明:偏心方形管内存在着强烈的传热不均匀现象,在远离大比热区的低焓值区和高焓值区,偏心距离的增加对内壁温度和换热系数的影响不大。随着偏心距的增加,方形管壁面最高温度逐渐升高,边通道传热系数要强于角通道;超临界水的物性变化也会影响偏心方形管内周向不均匀性,从而影响传热特性。     

滑动轴承非线性动态油膜压力分布特性的研究

针对有限长径向滑动轴承非线性动态油膜压力的分析与计算，定量阐明了非稳定润滑油膜的动态压力特性，进一步研究了轴承中转子自转速度、涡动速度及转子偏心速度等参数，对非线性油膜压力分布变化规律的影响。     

开裂纹转子的动力分析

以水平放置Jeffcott裂纹转子为研究对象，建立了弯扭耦合振动的非线性运动微分方程，并用数值方法分析了纯弯曲振动与弯扭耦合振动情况下的转子的动力响应。结果表明：弯扭耦合振动是通过不平衡量来实现，当不平衡偏心很小时可以不考虑扭转振动的影响。当不平衡偏心较大时，扭转对弯曲振动的影响主要体现在高转速部分，且随裂纹深度的增加，影响的转速下限就会越低，所以当裂纹较浅，转速较慢时可不考虑扭转的影响，但当裂纹较深，转速较快时，扭转对弯曲振动有明显的影响，使频谱图和轴心轨迹都发生较大的变化，且对转速的变化极为敏感。因此在故障诊断时必须对扭转的耦合作用高度重视。     

汽轮机转子涡动汽流激振力分析与CFD数值模拟

汽轮机转子涡动时轴心偏离静子中心产生轴系失稳的Thomas/Alford汽流激振力,传统的叶顶间隙激振力公式对此不能全面准确评估。该文综合考虑转子涡动以及围带汽封二次流,在动叶通道,根据蒸汽做功分析涡动效应激振力;在叶顶围带汽封,用CFD数值模拟泄漏蒸汽三维粘性流场,确定蒸汽激振力。研究结果表明小的静偏心和动偏心条件下,转子涡动动偏心在动叶通道诱发的激振力要大于静偏心激振力;围带汽封汽流预旋速度对间隙激振力有重要影响;调门不对称进汽也是蒸汽激振力的另一个重要来源。     

压气机动叶CLOCKING效应对叶片可靠性影响的数值研究

采用基于谐函数(harmonic)的非定常计算方法,数值模拟了某型燃气轮机中间三级轴流压气机流场,研究第二级动叶CLOCKING效应对中间级静叶片气动负荷的影响。通过对各列叶片非定常气动力和气动力矩进行时域分析,指出不同CLOCKING位置对应的气流激振力对叶片的气动负荷造成了明显的影响。进行了中间级动叶和静叶的振动可靠性分析。计算结果表明,该压气机的3组静叶片避开共振区的程度各不相同。R2转子叶片处于不同的CLOCKING位置会引起下游S2静叶片气流激振力发生显著变化,导致S2叶片产生比较强烈的共振。     

New vortex‐lift and tangential‐force models for HAWT aerodynamic load prediction

Horizontal axis wind turbines (HAWTs) experience three‐dimensional rotational and unsteady aerodynamic phenomena at the rotor blades sections. These highly unsteady three‐dimensional effects have a dramatic impact on the aerodynamic load distributions on the blades, in particular, when they occur at high angles of attack due to stall delay and dynamic stall. Unfortunately, there is no complete understanding of the flow physics yet at these unsteady 3D flow conditions, and hence, the existing published theoretical models are often incapable of modelling the impact on the turbine response realistically. The purpose of this paper is to provide an insight on the combined influence of the stall delay and dynamic stall on the blade load history of wind turbines in controlled and uncontrolled conditions. New dynamic stall vortex and nonlinear tangential force coefficient modules, which integrally take into account the three dimensional rotational effect, are also proposed in this paper. This module along with the unsteady influence of turbulent wind speed and tower shadow is implemented in a blade element momentum (BEM) model to estimate the aerodynamic loads on a rotating blade more accurately. This work presents an important step to help modelling the combined influence of the stall delay and dynamic stall on the load history of the rotating wind turbine blades which is vital to have lighter turbine blades and improved wind turbine design systems.     

气流力、油膜力和质量偏心共同作用下的转子非线性动力学研究

以Jeffcott转子系统模型为研究对象,利用气流力模型和非稳态油膜力模型对转子运动的动力学特性进行研究。研究方法采用数值模拟技术,研究了转子系统的分岔和混沌特性,并且对随转速变化和转子质量偏心率的变化时转子的运动特性进行了详细的分析和研究。研究结果表明,在转速变化时,系统在经历周期运动之后进入混沌状态,在质量偏心率增大时,系统在油膜力、气流力和不平衡偏心质量的影响下,系统由概周期运动进入混沌状态。     

Load control on a dynamically pitching finite span wind turbine blade using synthetic jets

The feasibility of active flow control, via arrays of synthetic jet actuators, to mitigate hysteresis was investigated experimentally on a dynamically pitching finite span S809 blade. In the present work, a six‐component load cell was used to measure the unsteady lift, drag and pitching moment. Stereoscopic Particle Image Velocimetry (SPIV) measurements were also performed to understand the effects of synthetic jets on flow separation during dynamic pitch and to correlate these effects with the forces and moment measurements. It was shown that active flow control could significantly reduce the hysteresis in lift, drag and pitching moment coefficients during dynamic pitching conditions. This effect was further enhanced when the synthetic jets were pulsed modulated. Furthermore, additional reduction in the unsteady load oscillations can be observed in post‐stall conditions during dynamic motions. This reduction in the unsteady aerodynamic loading can potentially lead to prolonged life of wind turbine blades. Copyright © 2014 John Wiley & Sons, Ltd.     

Aerodynamic loads on wind turbine nacelles under different inflow turbulence conditions

The aerodynamic loads on wind turbine nacelles for range of inflow turbulence conditions are investigated. To this end, a series of wind tunnel experiments are conducted to investigate pressure field distributions over the surface of scaled models of rectangular and ellipsoidal nacelles. It is found that the mean pressure fields on the roof of the rectangular nacelle are similar for all the inflow turbulence cases for respective yaw angles. However, when yaw angle is around 90°, the mean pressure coefficient becomes more negative close to upstream edge with increasing inflow turbulence. For the ellipsoidal nacelle, the magnitude of the mean pressure coefficient increases with decreasing inflow turbulence in the adverse pressure gradient region, although the minimum peak pressure coefficient remains unaffected by inflow turbulence. The overall effect of wind‐induced load on the nacelle surfaces is evaluated by computing force coefficients from the pressure data. It is observed that the peak force coefficients for both rectangular and ellipsoidal nacelles increase with increasing inflow turbulence. The models for the estimation of peak aerodynamic loads on the nacelle surfaces are proposed as functions of inflow turbulence and mean force coefficients and show satisfactory agreement with measurements. Finally, the loads calculated by the GL guideline are compared against the measurements. It is found that the guideline estimation is conservative for design load case (DLC) 6.1, but it underestimates the load by about 35% for DLC 6.2 when the inflow turbulence intensity is 13.2%.     

振荡扰流提高风力机翼型气动性能的研究

利用振荡扰流进行了改善风力机翼型大攻角下性能的研究。应用有限体积法，数值模拟了头部附加振荡扰流的翼型分离流动，并对振荡扰流增升效果的参数影响进行了分析。结果表明在深失速条件下，翼型头部附加的振荡扰流在一定的频率和振幅时能够显著改善翼型的气动性能，提高翼型的升力。与扰流振幅相比，调节扰流振荡频率更能改善翼型深失速条件下的气动性能。     

Extracting the angle of attack on rotor blades from CFD simulations

In today's wind energy research, comparisons of low‐fidelity aerodynamic models with CFD simulations are common practice. While the approach for loads with respect to the rotor‐plane coordinate system such as distributed driving force or thrust is straightforward, a comparison of aerodynamic characteristics is more challenging. The radial distributions of lift, drag, and moment coefficient depend on the local angle of attack and inflow velocity, which cannot be directly determined from the flow field. It requires the elimination of the influence of the rotor blade's bound circulation and also involves the step from a three‐dimensional flow field to quantities, which depend on the blade radius. The present investigation analyzes 4 different approaches to determine the angle of attack and inflow velocity from three‐dimensional rotor simulations. In addition to 3 existing methods, a new line average technique is presented. It eliminates the effect of bound circulation by averaging along a closed shape, which is symmetric to the quarter‐chord point. All methods are assessed in cases with successively increasing complexity. The observed discrepancies are assigned to a different consideration of trailing and shed vortices. The line average approach was found to be a valuable alternative to existing approaches especially in unsteady cases and regarding the outer or tip sections of the rotor blade.     

导流凸台对船舶汽轮机阀门非定常气动特性影响的DDES数值研究

针对某船用2.5 MW汽轮机组调节阀门在小开度运行下的非定常气动特性,采用延迟分离涡模拟（DDES）开展了全三维数值模拟。重点评估了阀座表面安装导流凸台对该阀门的阀碟气动力波动和扩压管内非定常蒸汽流场的影响。研究表明：在阀门喉部上游阀座处安装导流凸台后,阀门内部的主要流态从壁面分离流动转变为壁面附着流动,有效降低了阀门内的压力脉动幅值;安装导流凸台可以显著降低阀碟在轴向及侧向上的气动力波动幅值,轴向气动力波动幅值降低约51%,侧向气动力波动降低约34%。     

考虑kick效应的汽轮机调节级叶片安全性分析

采用喷嘴配汽的汽轮机调节级，部分进汽不仅对机组的气动性能和效率产生影响．而且还会产生很强的汽流激振力，影响到其自身和整个机组的安全性能。文章首先基于ANSYSCFX，计算了某调节级叶片的全三维气动特性．对调节级非定常气动特性和汽流激振力的变化进行了研究．分析得到了动叶进出不进汽弧段所受到的汽流载荷急剧变化的现象，该现象被称之为调节级的kick效应；然后基于ANSYS的结构动力学模块．考虑kick效应对调节级动叶在考虑气流载荷下的动响应进行了分析；最后，根据动响应计算结果，对调节级的安全性进行了评价。整个研究过程和结论．对于调节级的安全性设计具有重要的工程参考价值和指导意义.     

防旋板高度对迷宫密封泄漏流动和转子动力特性的影响

采用基于转子多频椭圆涡动模型的Unsteady Reynolds-Averaged Navier-Stokes (URANS)方程求解方法,研究了防旋板高度与第1个迷宫齿前缘高度相同时,防旋板高度对迷宫密封泄漏流动和转子动力特性系数的影响.计算分析了典型中等进口预旋条件下,无防旋板结构以及防旋板高度为1.85,3.7和...