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.     

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。     

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.     

液体环形密封转子动力特性CFD数值计算分析

首先研究建立环形密封物理模型和划分计算区域网格的方法;然后选择计算模型,确定边界条件,利用有限体积法的CFD-Fluent软件,计算该密封流体激振力和泄漏量;最后依据转子动力模型和激振力方程,计算环形密封动特性系数,与Lindsey的实验结果和Childs的理论计算结果进行了比较,结果表明本文的CFD数值计算结果比基于整体流动理论的计算结果更接近实验值。     

大型汽轮发电机组低频振动故障案例研究与分析

大型电站机组低频振动故障是现场常见的故障,低频振动故障包括油膜涡动、油膜振荡、汽流激振、动静碰摩及大不平衡、随机振动和分数谐波振动,处理不当可能引起严重后果。通过对低频振动案例整理分析,总结了各低频振动故障发生情况;归纳总结了各低频振动故障原因,轴颈挠度过大和轴承的影响是油膜振荡故障的两大原因,汽流激振故障原因包括机组运行不当、不良结构状态和轴承3个方面的影响;并在低频振动频率、低频振动幅值、与运行参数的关系3个方面,对比分析油膜振荡和汽流激振故障特征,为同类故障诊断及处理提供参考信息。     

600 MW汽轮机叶轮偏心汽流激振力分析与模拟

以某发电厂超临界600 MW汽轮机转子为研究对象,根据蒸汽做功原理对动叶流道处的动偏心激振力进行了分析.在围带汽封处采用CFD软件模拟涡动转子泄漏蒸汽的三维黏性流场,确定了汽流激振力.计算结果表明:在不对称进汽工况下,转子将受到较大的静态汽流力;当采用对称进汽时,汽流激振力很小,有利于提高转子的稳定性;与额定工况比较,在阀门全开(VWO)工况下,径向激振力的增幅很大,而切向激振力和泄漏量的增幅却很小,表明大型汽轮机采取对称进汽方式可以提高转子运行的稳定性.     

基于阶比分析的转子系统油膜涡动故障诊断研究

针对转子升速过程中油膜涡动信号的非平稳特点,将阶比分析应用于油膜涡动故障诊断中。首先对转子升速时的振动信号进行时域采样,再对时域信号进行等角度采样,将其转化为角域平稳信号,然后对角域信号进行频谱分析识别油膜涡动故障频率。对实测油膜涡动信号分析表明,阶比分析能有效地避免传统频谱分析方法中的"频率模糊"现象,能够准确识别转子升速过程中油膜涡动故障频率。     

船用汽轮机的振动问题

分析了船用高速汽轮机产生突发性低频振动的机理,指出部份负荷时的不平衡激振力及轴承较差的稳定性是试车时转子轴颈涡动的主要原因。根据振动频率小于转动频率之半,且不随转速变化的自激振动特点,采取了改进轴承参数的措施,取得了显著的效果。     

转子系统油膜涡动及油膜振荡故障特征分析

介绍了转子系统油膜涡动及油膜振荡的产生机理和故障特征。对转子实验台升速过程的振动信号进行了分析,揭示了转子系统油膜涡动和油膜振荡的发生过程。对典型油膜涡动和油膜振荡信号进行了时频分析,揭示出油膜涡动和油膜振荡的故障特征。     

气流激振力作用下碰磨转子的分叉现象

采用超超临界压力是提高汽轮机热效率的重要途径。随着蒸汽参数的提高,作用在转子上的激振力将显著增大,使得机组发生气流激振的可能性远远大于亚临界机组,因此有必要对气流激振作用下转子的非线性动力学特性加以研究。本文采用双控体模型来计算气封腔内的蒸汽对转子的激振力,分析了气流激振力作用下的碰磨转子的分叉特性。着重讨论了输入气压、密封间隙及转子转速等决定气流激振力大小的因素对碰磨转子分叉特性的影响。研究结果表明,气流激振力将明显抑制碰磨转子的拟周期运动。这种抑制作用随着输入气压的升高、密封间隙的减小而增强。     

高低齿汽封与蜂窝汽封及孑L式阻尼汽封密封性能的比较

使用商用CFD软件Fluent对高低齿汽封、蜂窝汽封及孔式阻尼汽封进行了三维数值模拟,得到三种汽封在不同压比、轴转速和汽封相对间隙时的密封性能,并将高低齿汽封和蜂窝汽封计算值与试验数据进行了对比．结果表明：高低齿汽封流量系数随压比增大而增大,随转速加快而略有减小,随相对间隙的增大而减小;蜂窝汽封与孔式阻尼汽封的流量系数均随压比增大而减小,随转速加快而略有减小,基本呈直线变化规律,随相对间隙的增大而增大;在相同的条件下,蜂窝汽封的漏汽量比高低齿汽封的漏气量减少10％,而孔式阻尼汽封的漏汽量比蜂窝汽封漏汽量减少6％．     

Numerical analysis of erosion of the rotor labyrinth seal in a geothermal turbine

Excessive erosion of the labyrinth seal of a 110 MW geothermal turbine has been investigated. This study used computational fluid dynamics (CFD) and aims to identify one cause of erosion and a possible solution for substantially reducing it. The predictions were based upon a numerical calculation using a CFD model of the labyrinth seal with a water/steam flow containing hard solid particles and solved with a commercial CFD code: Fluent V5.0. The results confirmed the existence of flow conditions that play a major role in the rotor labyrinth seal erosion. Afterwards, the flow path was simulated with changes of rotor labyrinth seal geometry, which are indeed feasible of being implemented. The results confirmed that it is possible to reduce the erosion process by approximately 80% by incorporating a steam flow deflector in the fourth stage diaphragm, which changes the steam flow direction in the inlet zone to the rotor labyrinth seal channel, resulting in a reduction in steam volumetric mass flow and hard particle velocity by about 44%.     

汽封力作用下的转子-轴承系统稳定性研究

通过分析汽封力对轴承静态平衡点的影响,表明汽封力能够改变轴承的静、动特性。计算了滑动轴承油膜力和汽封力共同作用下的系统一阶临界转速和一阶对数衰减率,并用实验进行了验证。研究表明,汽封力对系统稳定性的影响是复杂的,其影响因素包括进出口压力、进口预选速度、密封参数等。     

转子轴向偏移对交错齿迷宫密封动力特性的影响

为了分析汽轮机转子轴向偏移对交错齿迷宫密封动力特性的影响,建立了交错齿迷宫的三维CFD模型,并利用Fluent软件计算了在不同轴向偏移下的转子表面汽流力,得到了不同的动力特性系数.结果表明:交错齿迷宫密封的转子从中间位置逆着汽流方向发生轴向偏移后,系统的稳定性提高;反之,如其从中间位置沿着汽流方向发生轴向偏移后,则系统的稳定性降低.为此提出:在汽轮机安装时,使转子逆汽流方向有一定的热膨胀预留量,可提高系统的稳定性.     

Investigations of the conjugate heat transfer and windage effect in stepped labyrinth seals

In the current paper, conjugate heat transfer and windage heating in the stepped labyrinth seals with smooth and honeycomb lands are numerically investigated by using the commercial software ANSYS CFX11.0. Firstly, the utilized numerical approaches, such as the turbulence model and grid independence analysis, are determined to ensure a suitable numerical method for the present study. Based on the obtained measurement data, the computed heat transfer coefficients on the rotor and stator surfaces are carefully validated. To reveal the influence of the solid domain on the heat transfer computations, the comparisons between the results with and without solid domain are performed. It shows that the predicted heat transfer coefficient distributions with the presented conjugate heat transfer methods (with solid domain) agree well with the experimental data. Difference between the numerical results with and without solid domain only exists in the high temperature gradient region. Compared to the smooth labyrinth seal, the presence of honeycomb cells increases the temperature gradient in the labyrinth fin (solid domain) and significantly decreases the temperature gradient in the stator (solid domain). Secondly, in order to assess the influence of the rotating effect on the windage heating for the stepped labyrinth seal, total temperature difference between the seal inlet and outlet are computed under different effective pressure ratios for both the smooth and honeycomb configurations. Based on the energy conservation law, the windage loss for the high speed rotating seal is also obtained by taking the heat transfer between the fluid and solid into consideration. Finally, the influences of the effective pressure ratio and inlet preswirl ratio on the heat transfer coefficient distributions of rotor and stator for both the smooth and honeycomb configurations are discussed in detail.     

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...     

迷宫密封转子动力学特性的数值模拟

采用数值求解三维Reynolds-Averaged Navier-Stokes(RANS)方程,研究了具有16个齿的迷宫密封转子动力学特性,分析了在两种转速条件下进口预旋对迷宫密封转子动力特性系数的影响,计算了无进口预旋时,在两种压比条件下,迷宫密封系统的交叉刚度和直接阻尼系数随转速的变化关系,并将计算结果与实验值和两控制容积BF(Bulk Flow)方法计算值进行了比较.研究结果表明:所采用的数值方法能较好地预测迷宫密封的转子动力特性,且计算结果优于两控制容积BF方法.对于迷宫密封,交叉刚度与进口预旋近似成正比关系,且随着转速的增大而增大;直接阻尼对转速和进口预旋均不敏感,但随压比的增大而显著增大.过大的进口预旋和转速均会使转子的稳定性降低;工作在较大转速下的迷宫密封系统可以通过施加合理的进口预旋来增强转子的稳定性.     

Dimensional analysis on resistance characteristics of labyrinth seals

Experimental investigation of stepped and straight-through labyrinth seals was designed to study the sealing performance of two different typical labyrinth seals.In order to facilitate dimensional analysis on the flow resistance characteristics of labyrinth seals,the variable cross-section of the flow channels are considered as constant cross-section flow.The mechanical energy loss of flow caused by throttle turbulence intensity is considered as caused by friction along the way.The friction coefficient of stepped labyrinth seals is bigger than that of straight-through labyrinth seals by more than 40% for the same Reynolds number and the ratio of equivalent diameter and the seal length.The expression of friction coefficient /and /Re are obtained from experimental data.The verifications indicate that the expressions are highly accurate.The contribution to the total pressure drop of each tooth cavity gradually becomes less along the flow direction.     

基于声学有限元的柴油机增压器压气机气动噪声研究

为研究船用低速柴油机增压器压气机气动噪声,采用计算流体动力学和声学有限元的混合计算方法进行了数值预测。通过试验对压气机计算模型进行了验证。在3个工况下对压气机非定常流场进行了计算,其中压力脉动被用作声学计算中的声源信息;采用声学有限元方法对压气机气动噪声进行了预测。结果表明:计算流体力学和声学有限元的混合计算方法具有较高的计算精度,可以用于压气机气动噪声数值预测;压气机进口气动噪声主要谱成分为离散单音噪声和宽频噪声;离散单音噪声在叶片通过频率处有明显的指向性,存在两个突出峰值。     

节流件阻力特性的CFD研究

增加沸腾管入口段流动阻力是抑制沸腾管内流动不稳定性的主要措施之一。本文采用商用CFD软件CFX对带有微小节流件的沸腾管入口段进行计算分析,得到了计算该段摩擦阻力的关系式,并能与现有的实验数据吻合。