多因素下迷宫密封泄漏分析及实验验证

Analysis and experimental verification on the leakage of labyrinth seals under multiple factors

迷宫密封作为转轴密封的主要形式,被广泛应用于离心式压缩机、航空发动机和膨胀透平机等旋转机械。为提高迷宫密封的密封性能和满足现代旋转机械需求,需要从多角度开展迷宫密封的结构优化研究。该文基于FLUENT软件进行迷宫密封流场仿真,采用计算流体动力学(computational fluid dynamics, CFD)方法,分析了迷宫密封几何参数及齿形结构对泄漏量的影响规律;提出了占空比、深宽比2种参数定义,通过调整参数设置,可以消除空腔高度、空腔宽度、齿厚和齿距4种参数间的耦合影响,可为参数优化设计提供重要参考;建立了高转速迷宫密封实验系统,通过实验验证,仿真结果最大误差仅为3%。结果表明:在工况参数中,压差对泄漏量具有显著影响,而转速基本不会影响泄漏量;在几何参数中,密封间隙对泄漏量具有显著影响,而占空比、深宽比和齿距对泄漏量的影响较小;在齿形结构中,斜齿具有更小的泄漏量,并且减小前齿与后齿倾斜角将有益于降低泄漏量。

[Objective]As the main form of shaft seal,labyrinth seals provide several advantages,such as simple structure,convenient disassembly and assembly,and the ability to withstand high pressure and other harsh working conditions.They are widely used in centrifugal compressors,aeroengines,expansion turbines,and other rotating machinery.The diversity of labyrinth seal structures and the complexity of real working conditions make its internal gas flow and heat transfer very complex.The current literature reveals several factors that affect the leakage of labyrinth seals;however,comprehensive studies on the leakage characteristics of the multifactor coupling effect have been scarce.To improve the sealing performance of the labyrinth seal and reach the development trend of modern rotating machinery,performing detailed research on the structure optimization of labyrinth seals from multiple angles is crucial.[Methods]In this study,the flow field of the labyrinth seal was simulated by FLUENT software,the influences of geometric parameters and tooth structure of the labyrinth seal on leakage were analyzed by computational fluid dynamics(CFD).The labyrinth seal experimental system was established,which could realize the labyrinth seal experimental conditions under a maximum speed of 10000 r/min and a gas supply pressure of 0.6 MPa.[Results]The experimental results exhibited that in the operating parameters,the pressure difference had a significant impact on the leakage,while the speed basically had no impact on the leakage.Moreover,comparison of the experimental results with the mathematical model showed that the maximum error between the mathematical model and the experimental results was 3%.The orthogonal experiment results indicated that the geometric parameters of the four tooth profiles had different degrees of influence on the leakage.Thus,the seal clearance had a remarkable effect on the leakage,while the duty cycle,depth width ratio,and tooth pitch had little effect on the leakage.After analyzing the tooth shape parameters,it was found that in the tooth shape structure,the inclined teeth had smaller leakage and reducing the inclination angle between the front teeth and the rear teeth would be beneficial to reducing the leakage.Analysis of the number of sealing teeth revealed that increasing the number of teeth was conducive to reducing the leakage without increasing the axial length.Moreover,this phenomenon was more obvious with increasing pressure difference.Therefore,when the total pressure difference was a constant value,the impact of the increasing number of teeth on the leakage rate would not change significantly.[Conclusions]In this study,the CFD model of the labyrinth seal is established by FLUENT software,and the internal flow field distribution and leakage characteristics of the labyrinth seal are revealed.Two geometric mechanism parameter definitions,namely,duty cycle and depth width ratio,are proposed.The parameter definition can effectively eliminate the coupling effect between the parameters,such as tooth height and tooth thickness,and provide an important reference for parameter optimization design.A sealing experimental system that can realize the working conditions of high speed and large pressure difference is generated and can monitor the leakage in real time.Moreover,the impacts of the working condition parameters,geometric parameters,number of seal teeth,and structural parameters on the leakage of the labyrinth seal are studied by the CFD model.This study is of great importance for the structural design of labyrinth seals.