基于FLUENT迷宫密封动力特性分析

利用CFD有限元软件Fluent计算迷宫密封三维流场,提出一种计算密封动力特性系数的方法,并研究了偏心率、入口预旋、涡动速度对转子密封动力特性的影响.计算结果表明:入口预旋是产生交叉刚度的主要原因,入口预旋越大交叉刚度越大;主刚度和交叉阻尼与偏心率的关系基本上是线性的,而交叉刚度和主阻尼随偏心率变化呈现明显的非线性.交叉刚度和主阻尼是影响密封转子系统稳定性的重要因素.     

迷宫密封临界稳定性研究

建立迷宫密封试验装置与数值分析模型,开展静态与动态稳定性分析,研究进口压力、转速及密封齿数对系统稳定性的影响,并以密封腔为单元对密封段转子受力进行分解,分析各密封腔对密封段转子整体切向气流力影响,提出"穿越齿数"与"临界稳定性"概念。研究表明:各密封腔对应转子切向气流力方向沿泄漏方向逐渐变化,并存在一个使切向气流力为零的穿越齿数。当密封齿数小于穿越齿数时,密封静态交叉刚度均为负值,且稳定性随转速与进口压力的提升而增加;当密封齿数大于穿越齿数时,密封静态交叉刚度均为正值,且稳定性随转速与进口压力的增加而降低;当齿数等于穿越齿数时系统处于临界稳定状态,切向气流力接近于零;转子涡动频率的增加将增大穿越齿数。     

轴承阻尼对高转速离心泵临界转速的影响

采用商用软件计算了泵用三油楔滑动轴承刚度和阻尼曲线。以多级离心泵转子为研究对象,采用ANSYS软件建立了三维转子有限元模型,在考虑滑动轴承和密封刚度、阻尼系数的情况下进行转子"湿"临界转速分析,计算结果表明在Campbell图中出现了低频涡动频率,且临界转速裕度不足。通过对滑动轴承主刚度、交叉刚度、主阻尼和交叉阻尼对涡动频率的分析得出,轴承主阻尼系数是产生该现象的主要原因。最后通过增加轴承孔半径0.01 mm,降低主阻尼系数,提高了涡动频率和临界转速,为多级离心泵动力学设计提供参考。     

基于动网格模型的液体动静压轴承刚度阻尼计算方法

针对雷诺方程不能反映高速油流周向惯性效应、轴颈周向动压效应和静压扩散效应之间的非线性耦合关系及其对三维流场特性的影响,进而导致动静压轴承刚度阻尼的计算精度难以满足高转速精密轴承设计需要之现状,提出基于纳维-斯托克斯方程的动网格计算轴承刚度阻尼新方法。该方法采用自定义程序实现轴颈的旋转速度、位移扰动和速度扰动以及扰动过程中油膜力的计算等功能,成功将轴颈的旋转动边界转换为静边界,有效避免因轴颈旋转引起的网格畸变,并利用弹簧光顺模型更新轴颈受速度扰动和位移扰动引起的油膜网格挤压变形。通过对比研究瞬态和稳态条件下油膜力的变化,界定计算刚度阻尼系数时速度扰动和位移扰动的合理取值范围。利用所提出的方法计算典型轴承的刚度阻尼系数,再现动静压轴承油膜厚度和三维流场压力分布的动态发展过程,并采用影响系数法对该轴承的刚度系数进行试验测试。通过对比试验数据和动网格计算结果发现两者基本吻合,表明所提出的计算方法是有效可行的。     

不同载荷作用下航空发动机前支承动刚度的有限元计算

目前航空发动机转子支承结构的动刚度计算不准确,严重影响转子动力特性计算结果的准确性.为此建立不同的转子支承结构三维模型,分别施加分布载荷和集中载荷并用有限元软件对其进行频率响应计算,再由所得位移曲线求出相应的动刚度曲线,然后进行对比分析.得出分布载荷的施加方法更符合实际发动机转子支承结构的受力情况,计算动刚度结果更加准确.最后给出一个求某型航空发动机前支承处动刚度的算例.所采用的计算方法和得到的结果对发动机转子支承结构的动刚度计算具有一定的参考价值.     

250 t高速动平衡机摆架的动刚度分析

高速动平衡机摆架的动力学性能直接影响动平衡试验的准确性及安全性。采用三维有限元法建立某公司250 t高速动平衡机摆架的计算模型,并对其动刚度进行计算分析,且与试验值进行比较。在此基础上计算4种主刚度杆改进方案下摆架的动刚度特性,分析主刚度杆的刚度对高速动平衡机摆架的动刚度曲线的影响。结果表明,计算所得摆架的动刚度曲线与实测值吻合较好,该计算模型接近实际情况。主刚度杆的结构尺寸及材料的弹性模量的增大均会使摆架的动刚度增大,适当地改变主刚度杆的结构尺寸及材料特性,可使高速动平衡机摆架满足大质量转子的高速动平衡试验要求。通过主刚度杆的改进并不能使摆架的动刚度随转速变化的曲线趋于平缓。     

进口总压畸变对压气机性能及流场影响的机理研究

采用全三维非定常数值方法研究进口周向总压畸变对轴流压气机转子性能及内部流场的影响,数值结果表明进口周向总压畸变后不仅降低压气机的稳定裕度,也使压气机等熵效率减少。通过详细地分析压气机内部流场,揭示了进口周向总压畸变对该压气机转子性能及流场影响的机理,即进口周向总压畸变后,明显降低50%～100%叶展内的气流进气角。同时增强产生叶尖泄漏运动的驱动力,提前使叶顶间隙泄漏涡涡核破碎,造成高的堵塞,最终触发压气机失速。     

基于不平衡响应的转子动刚度测量方法

基于转子不平衡响应原理,推导了转子动刚度计算方法,建立了一种转子系统动刚度测量方法。在某双盘转子试验器上开展了转子动刚度测量实验。实验结果表明:由转子动刚度曲线计算的一阶临界转速最大误差为1.5%;以盘一、盘二处的轴系静刚度为基准,由动刚度曲线计算的轴系静刚度最大测量误差为5.7%。利用转子动刚度研究了不同支座地脚螺栓拧紧力矩对转子系统的影响,结果表明:当支座反力小于支座拧紧力矩所能产生的最大静摩擦力时,增加支座连接刚度并不会改变转子系统的动刚度。     

新型涡流槽密封泄漏特性与动力特性研究

提出一种密封入口周向均匀设置有涡流槽的新型密封结构,建立了传统迷宫密封与新型涡流槽密封泄漏特性及动力特性求解模型,在实验验证数值计算方法准确性的基础上,通过比较分析了传统迷宫密封与新型涡流槽密封在不同进出口压比、预旋比工况下的泄漏特性与动力特性,研究了新型涡流槽结构对密封泄漏特性及动力特性的影响机理。研究结果表明：随着涡流槽数量的增加,涡流槽密封的泄漏量逐渐降低;在同一压比下,不同涡流槽数新型密封的泄漏量之间差值随着压比的增大而增大。当压比为6时,64涡流槽的新型密封较传统迷宫密封,泄漏量下降了3.37%;在高预旋比的工况下,不同涡流槽数量密封的切向气流力均与转子涡动方向相反,起到抑制转子涡动的作用,且随着涡流槽数量的增加,切向气流力也随着增大;随着转子涡动频率的增大,三种不同涡流槽数量密封的交叉刚度先减小到负值然后增大到正值。涡流槽密封的有效阻尼均高于传统迷宫密封,新型涡流槽密封可以提高转子系统的稳定性。     

一种永磁轴承的刚度特性分析

介绍了一种混合型磁悬浮轴承及其工作原理，根据磁荷法原理对一个有具体参数的径向磁轴承进行了磁力计算，对计算结果数据应用MATLAB软件求出了转子在各种位置时受到的磁力的数据，建立了转子的刚度矩阵，分析了各主刚度与牵连刚度特性。分析结果表明：该径向磁轴承在转子径向及偏转微动时具有使其自动稳定的能力。     

A novel negative dislocated seal and influential parameter analyses of static/rotordynamic characteristics

This paper proposes a new type of negative dislocated seal (NDS) based on the dislocated bearing theory to investigate the influential parameters of static rotor eccentricity and dislocated ratio on the static and rotordynamic characteristics of an example seal solved with computational fluid dynamics (CFD) the flow field. The rotordynamic characteristics of the NDS were investigated in respect of the effects of rotor whirling frequency on response force, stiffness coefficients, damping coefficients and rotor system stability, by multifrequency elliptical orbit rotor whirling model. Based on the studies, we reached the following conclusions. The circumferential pressure distribution of NDS and conventional labyrinth seal (LS) presents sine periodic variation approximately, while relative to the LS, the NDS has two divergent wedge gaps and reduces the hydrodynamic pressure effects, then the circumferential pressure difference and tangential force on rotor surface decreases by about 40 %~190 %. The leakage of the NDS linearly increases with the rising eccentricity ratio and dislocation ratio approximately, and is larger (about 0.9 %~1.5 %) than the LS. The direct stiffness coefficients of the two seals increase with the rise of rotor whirling frequency, while the absolute values of both the cross-coupled stiffness coefficients and the damping coefficients decrease with raising rotor whirling frequency. Compared with the LS, the NDS has smaller (about 28.8 %~206.2 %) cross-coupled stiffness coefficient, larger (about 26.15 %~60.39 %) effective damping coefficient, and good stability of rotor system. This study has developed a novel seal structure to improve the seal performance of turbomachinery such as aeroengine.     

设计工况下离心压气机内部动静部件耦合非定常流动的数值模拟

以设计工况下离心压气机内部动静部件耦合的非定常流场为研究对象,采用ＰＩＳＯ算法求解了包含绝对速度与相对速度的、统一形式的运动方程组。计算结果与试验测量结果比较,说明计算结果是可靠的;计算结果同时说明,只有采用非定常算法,才有可能较好地描述动静部件耦合的流场。     

An experimental identification model of rotordynamic coefficients of seals using unbalanced synchronous excitation method

This study presents an improved impedance method based on unbalanced synchronous excitation to identify the rotordynamic coefficients of labyrinth seals. The rotordynamic coefficient test is implemented near the cylinder resonance frequency to enlarge the influence of seal force. The force generated by the rotor unbalance is used to provide synchronous frequency excitation for the rotordynamic coefficient test. Four unique equations are set up under two sets of different rotor unbalance conditions to obtain four unknown complex rotordynamic coefficients. The factors that influence the rotordynamic coefficients of seals, namely, unbalance mass, inlet/outlet pressure ratio, and rotating speed, are considered. The dynamic coefficients are minimally affected by different rotor unbalances. The direct items are nearly equal with same signs, whereas the cross-coupled items are nearly equal with opposite signs. All coefficients increase with increasing inlet/outlet pressure ratio and rotating speed. The direct stiffness coefficients increase more quickly than the cross-coupled items. In addition, the effect stiffness and effect damping coefficients are analyzed; results indicate that both coefficients increase with increasing rotating speed.     

三维转子密封系统气流激振的研究

提出了分析三维转子密封系统气流激振流固耦合作用的数值计算方法。首先建立三维转子密封流固耦合模型,然后直接数值求解密封流场的非线性气动力,形成了考虑流固耦合效应的转子密封气流激振问题的分析方法。数值计算表明,对应于不同的转速、压比和预旋,转子振动的各个频率成分的幅值不同,但始终存在着转子一阶临界转速频率成分,而且该成分的幅值随着转速、气流进口压力和正向进气预旋的增高而增大,与工程和试验中的密封气流激振现象有较好的一致性,捕捉到了密封气流激振的基本特性。     

NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER

The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder.     

Nonlinear Numerical Prediction of a Rotor–Bearing System Using Damped Flexure Pivot Tilting Pad Gas Bearings

Flexure pivot tilting pad gas bearings with pad radial compliance (FPTPGB-Cs) and metal mesh dampers (MMDs) in parallel (FPTPGB-C-MMDs) have been considered for application to high-speed and high-performance turbomachinery because of their advantages of high effective damping level and adequate compliance with variations in rotor geometry or misalignment. Although the dynamic coefficients of FPTPGB-C-MMDs have been predicted using the linear method, a nonlinear study is urgently needed for their high nonlinear behavior. A nonlinear numerical investigation on the rotor–bearing system supported by FPTPGB-C-MMDs is presented in this study by using the time domain orbit simulation method that couples rotor motion equations, the unsteady Reynolds equation, and pad motion (considering MMDs) equations. The nonlinear predictions are verified by the prediction and experimental results of a published paper.FPTPGB-C-MMDs can effectively suppress the subsynchronous vibrations compared with the rotor system supported by FPTPGB-Cs. The prediction results show that a high damper mesh density has a more positive effect on improving the stability of the rotor system by reducing the subsynchronous vibrations. Investigation shows that MMDs can improve the ability of the rotor system to sustain the effect of destabilizing forces. A high damper mesh density can sustain large destabilizing forces. The simulation results also indicate that low pad radial stiffness or preload leads to high amplitudes of subsynchronous vibrations. A small clearance results in an increase in critical speed and its synchronous amplitude. Moreover, large clearance results in a wide speed range that leads to the occurrence of subsynchronous vibrations with large amplitudes.     

隐极发电机转子扭转刚度的边界元法分析

应用非圆截面柱体的扭转理论分析了隐机发电机转子的扭转刚度问题,得到了两极型隐极发电机转子扭转刚度的边界元解,讨论了转子极夹角和导线槽对扭转刚度的影响。与有限元结果比较,本文方法具有计算简便、准确的优点。     

基于Kriging插值的失谐叶盘气动 结构耦合振动特性分析

以某型航空发动机压气机转子为研究对象,考虑叶盘间动静干涉的影响,对压气机叶盘转子内部的三维流场进行了模拟。通过静频试验引入叶片失谐量,基于Kriging模型完成了耦合界面载荷数据的传递,分析了压气机转子叶片表面非定常气动载荷的分布规律,并讨论了失谐和气动载荷对压气机转子叶盘系统振动特性的影响。结果表明：压气机叶片受到的气动载荷为非定常脉动压力,主导频率为动静干涉频率f0的倍频;在干涉周期T内,压力面和吸力面气动载荷的变化呈相反趋势,且压力面气动载荷的非定常性明显大于吸力面气动载荷的非定常性;失谐和气动载荷的作用加剧了叶盘系统的振动。研究结果为压气机叶盘转子系统的动力学设计提供了理论依据。     

离心压缩机蜂窝阻尼密封动力特性及转子稳定性*

新一代蜂窝阻尼密封在提升透平机械转子稳定性方面有优越的表现,其动力特性是评价转子稳定性的重要参数。应用非定常动网格技术和多频涡动模型,研究蜂窝密封动特性系数随转子涡动频率的变化规律,并与迷宫密封进行对比。结果表明：蜂窝密封动特性受转子涡动频率影响较大,直接刚度系数和交叉阻尼系数随涡动频率增大而增大,交叉刚度和直接阻尼系数随涡动频率增大而减小;迷宫密封动特性系数随涡动频率变化特征不明显;在低频率区蜂窝密封的有效阻尼远高于迷宫密封。在实际压缩机转子上的应用结果表明,蜂窝密封能显著提升转子稳定性。     

对转风扇排间干涉效应对下游转子颤振特性影响的数值模拟研究

为了探究对转风扇排间干涉效应对下游转子颤振特性的影响,在多叶排环境下,使用谐波平衡法进行振荡叶片非定常流数值模拟。通过颤振预测的能量法考察两种不同多排模型下叶片表面非定常压力响应和气流做功的差异,探讨了对转结构下上游扰动对下游转子气动弹性稳定性的作用机制。研究结果显示:下游振荡叶排的气动阻尼因上游转子的气动干涉而降低,造成这种颤振特性差异的主要原因除了排间非定常扰动引起时均流场中激波形态的变化,还有上游尾迹传播引发的下游转子进口气流角的周期性波动。