袋型阻尼密封泄漏特性和转子动力特性的研究

发布时间：2018-03-20 03:21

  本文选题：袋型阻尼密封　切入点：泄漏特性　出处：《西安交通大学》2017年博士论文　论文类型：学位论文

【摘要】：旋转密封是叶轮机械中的关键部件,控制着通过动静间隙从高压区域向低压区域的泄漏流动。虽然旋转密封的主要功能是抑制泄漏流动,但其在控制泄漏流动的同时会产生流体激振力,对叶轮机械的转子系统稳定性具有显著影响。相比于传统的迷宫密封,袋型阻尼密封具有与之相近的密封性能和非常优越的抑制转子振动的能力,目前被应用于多级高转速离心压气机中,替代迷宫密封达到控制泄漏和改善转子系统稳定性的目的。本文的主要目的是通过对袋型阻尼密封泄漏特性和转子动力特性的深入研究,阐明其密封和阻尼机理。首先,针对高参数叶轮机械中旋转密封有效间隙会在高转速作用下偏离其设计值的问题,率先提出了适用于袋型阻尼密封在高转速下、考虑流固耦合效应时的泄漏特性研究的有限元分析(FEA)和计算流体动力学(CFD)相耦合的数值方法(FEA/CFD),系统分析了运行工况和几何参数对袋型阻尼密封泄漏特性的影响,得出了相应的泄漏特性曲线。计算了典型袋型阻尼密封实验件在3种转速、3种压降下的泄漏量,数值结果与实验值吻合良好,验证了FEA/CFD数值方法的准确性和有效性。在此基础上,研究了压比、密封间隙和转速对袋型阻尼密封泄漏特性的影响规律,并与传统迷宫密封进行了比较。研究结果表明:高转速下,采用FEA数值方法考虑转子半径伸长的影响能够显著提高密封泄漏量的预测精度;相比于压比和转速,密封间隙对泄漏量的影响更为显著,周向挡板对泄漏量几乎没有影响;袋型阻尼密封泄漏量随压比的减小而增大,并逐渐趋于临界状态对应的最大值;高转速对泄漏特性的影响可分为两个方面:粘性耗散效应和几何效应;袋型阻尼密封的周向挡板结构能够显著地减小密封腔室内的周向旋流速度。其次,发展了一种基于Bulk Flow理论的适用于袋型阻尼密封转子动力特性系数预测的理想气体单控制体等温Bulk Flow计算模型和数值算法,并开发了具有自主知识产权的计算程序。计算了4种典型袋型阻尼密封实验件的频率相关的转子动力特性系数,预测结果与实验值吻合良好,验证了所发展的Bulk Flow计算模型和数值算法的有效性。选用目前常用的8种迷宫密封泄漏量预测模型,分析了泄漏量预测模型对所发展的Bulk Flow模型预测精度的影响,选出了最优的泄漏模型。在此基础上,研究了密封齿数、密封间隙、密封间隙比和腔室深度等几何设计参数对袋型阻尼密封转子动力特性的影响。结果表明:袋型阻尼密封的密封齿数和腔室深度均存在一个最优值使其具有最大的阻尼;较小的密封间隙对提高袋型阻尼密封的阻尼是有利的。再着,首次提出了预测旋转密封转子动力特性的多频涡动模型和非定常CFD数值方法,包括转子多频涡动位移的三种数学模型(直线涡动轨迹模型、圆涡动轨迹模型和椭圆涡动轨迹模型)、非定常流体激振力的CFD求解方法和转子动力特性系数的频域提取方法。基于多频椭圆涡动模型,计算分析了三种典型的旋转密封实验件(迷宫密封、袋型阻尼密封和孔型密封)在不同转速、进口预旋条件下、20~300Hz频率范围内的频率相关的转子动力特性系数,三种旋转密封的预测结果均与实验值吻合良好,验证了所提出的多频涡动模型和CFD数值方法的准确性和适用性。分析了多频涡动位移数学模型和湍流模型对预测结果的影响。研究结果表明:多频涡动模型只需进行一次非定常求解便可获得多个频率下的转子动力特性系数,具有预测精度高、计算速度快和对不同的旋转密封结构普遍适用的优点;多频涡动模型的预测结果不受转子涡动轨迹的影响;从预测精度和计算时间两个方面综合考虑,在旋转密封转子动力特性系数的数值预测中,标准k-?湍流模型是一种经济适用的湍流模型。最后,采用所提出的多频椭圆涡动模型和非定常CFD数值方法,系统全面地评估了运行工况(压比、转速、进口预旋)和几何结构参数(周向挡板数、腔室深度)对袋型阻尼密封转子动力特性的影响规律。研究结果表明:相比于密封出口压力,密封进口压力对袋型阻尼密封转子动力特性的影响更为显著;袋型阻尼密封的有效阻尼随进口压力的增大而显著增大;袋型阻尼密封更适宜安装在进口压力高,进出口压差大的位置。转速和进口预旋均使袋型阻尼密封的交叉刚度绝对值明显增大,使有效阻尼系数显著减小,其中进口预旋的影响更为显著。相比于迷宫密封,袋型阻尼密封能够提供更大的频率相关的直接刚度和直接阻尼;增加袋型阻尼密封的周向挡板数能显著地增大直接刚度,但对有效阻尼的增大效果有限。相比于直通光滑环形密封,袋型阻尼密封具有较大的直接刚度和较小的有效阻尼;袋型阻尼密封的腔室深度存在一个最优值使其同时具有较大的直接刚度和较大的有效阻尼。本文针对袋型阻尼密封在高转速下的非定常泄漏流动和转子动力特性开展了深入的数值研究。所提出的FEA/CFD耦合的泄漏特性数值分析方法、Bulk Flow分析模型和基于多频涡动模型的转子动力特性数值预测方法为进一步提高叶轮机械运行效率和稳定性的高性能袋型阻尼密封设计提供了理论基础和技术支撑。
[Abstract]:The rotary sealing is a key component in turbomachinery, controlled by clearance from the high pressure to low pressure leakage flow. Although the main function of rotating seal leakage flow is suppressed, but at the same time, the leakage flow in the control will produce fluid exciting force, has a significant impact on the stability of rotor system of turbine machinery. Compared to the the traditional labyrinth seal, pocket damper seal ability has the similar sealing performance and excellent suppression of rotor vibration, has been used in high speed multistage centrifugal compressor, instead of labyrinth seal to control leakage and improve the stability of the rotor system. The main purpose of this paper is through in-depth study of the characteristics and the seal leakage the rotor dynamic characteristics of the pocket damper, the sealing and damping mechanism. Firstly, aiming at the high mechanical parameters of the impeller rotating seal in effective clearance at The design value of the deviation from the high speed under the action, first proposed for pocket damper seal at high speed, the finite element analysis of the leakage of the fluid solid coupling effect considered (FEA) and computational fluid dynamics (CFD) numerical method of coupled system (FEA/CFD), analyzes the influence of operating conditions geometrical parameters and characteristics of the pocket damper seal leakage, leakage characteristic curves are obtained. The experiment in 3 kinds of sealing speed typical pocket damper was calculated, the 3 pressure drop under the leakage, numerical results are in good agreement with experimental results, verify the accuracy of the FEA/CFD value and the effectiveness of the method. On the basis of on the study of the ratio of pressure, the sealing effect of clearance and speed of the pocket damper seal leakage characteristics, and compared with the traditional labyrinth seal. The results show that the high speed, considering the rotor radius extension using FEA numerical method Long effect can significantly improve the prediction accuracy of leakage; compared to the pressure ratio and rotational speed, the sealing effect of the clearance on the leakage is more significant, the peripheral barrier has almost no effect on the leakage; leakage increases with the decrease of pressure ratio of pocket damper seal, the maximum value and gradually to the critical state of the corresponding high speed; influence on the leakage characteristics can be divided into two aspects: the viscous dissipation effect and geometric effect; pocket damper seal circumferential baffle structure can significantly reduce the sealing chamber circumferential flow. Secondly, the development of an ideal gas for Bulk Flow based on the theory of dynamic in pocket damper seal the prediction coefficients of rotor single control volume isothermal Bulk Flow calculation model and numerical algorithm, a computer program is developed with independent intellectual property rights. The calculated frequency of 4 typical experimental pieces of pocket damper seal The rotor dynamic coefficients, the prediction results in good agreement with experimental results, verify the effectiveness of the development of the Bulk Flow calculation model and numerical algorithm. The 8 kinds of commonly used labyrinth seal leakage prediction model, analyzes the leakage prediction model on the impact of Bulk Flow model development, selected leakage the best model. On this basis, the effect of sealing tooth number, seal clearance, seal clearance ratio and chamber depth geometric design parameters of the pocket damper seal rotor dynamic characteristics. The results show that the pocket damper seal teeth and chamber depth has an optimal value so that it has the maximum damping the smaller; the seal gap is favorable to improving the pocket damper seal damping. Then, for the first time put forward a prediction of multi frequency eddy rotary seal dynamic characteristics of rotor dynamic model and unsteady numerical method CFD, The rotor includes three kinds of mathematical models of multi frequency eddy displacement (the linear eddy trajectory model, circular whirl orbit model and elliptic vortex trajectory model), frequency domain from the unsteady fluid force CFD method and rotor dynamic characteristic coefficient method. A multi frequency elliptical vortex model based on calculation and analysis three typical rotary seal test (labyrinth seal, pocket damper seal and seal groove) at different rotational speed, inlet swirl, the frequency range of 20~300Hz frequency dependent rotordynamic coefficient, the three prediction results of rotating seal in good agreement with experimental results, verify the accuracy of the model and CFD the numerical method of multi frequency eddy and the applicability of the proposed analysis. The multi frequency eddy displacement mathematical model and turbulence model on the prediction results. The results show that the multi frequency eddy model only one unsteady solution will Can obtain the rotordynamic coefficients at multiple frequencies, with high accuracy and fast calculation speed of different rotary sealing structure has the advantages of universal application; effect of multi frequency eddy model prediction results are not affected by the rotor whirl orbit; considered from the two aspects of prediction accuracy and computation time, standard in k- numerical prediction of rotary seal rotordynamic coefficients in? Turbulence model is a turbulent economic applicable model. Finally, a multi frequency elliptical vortex with the proposed dynamic model and unsteady CFD numerical method, system and comprehensive assessment of the operating conditions (pressure ratio, rotational speed, inlet swirl) and geometric structure the parameters (circumferential baffle number, cavity depth) influence of rotor dynamic characteristics of the pocket damper seal. The results show that: compared to the seal sealing the inlet pressure outlet pressure, rotor dynamic characteristics of pocket damper seal more Significant; effective damping pocket damper seal with the increase of the inlet pressure increases significantly; pocket damper seal is more suitable for installation in the inlet pressure, outlet pressure difference large position. Increased cross speed and inlet pre swirl the pocket damper seal stiffness of the absolute value of the effective damping coefficient decreased significantly among them, the influence of inlet pre swirl is more significant. Compared to the labyrinth seal, pocket damper seal can provide more direct frequency dependent stiffness and damping directly; increase the pocket damper seal circumferential baffle number can obviously increase the stiffness, but the effective damping is increased compared to the limited effect. Through the smooth annular seal pocket damper seal effective damping has greater direct stiffness and smaller; the chamber depth of the pocket damper seal has an optimal value so that it also has a larger direct stiffness and more effective Damping. In this paper the pocket damper seal in high speed under the unsteady leakage flow and rotor dynamic characteristics was carried out extensive numerical simulations. Numerical analysis method of leakage characteristics of FEA/CFD coupling of the proposed Bulk Flow model and rotor dynamic characteristics numerical prediction method of multi frequency eddy model based on seal design the theoretical basis and technical support to further improve the performance of high damping bag type impeller mechanical efficiency and stability.

【学位授予单位】：西安交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH136
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本文编号：1637293