基于ANSYS的带簧油封径向力分析

提出一种考虑弹簧初应力的油封径向力有限元计算方法,即通过二维轴对称模型实现带簧油封的径向力计算。该模型中通过圆管来等效油封弹簧,并可以实现弹簧初应力现象的模拟;圆管模型的材料属性由2种状态下(弹簧装配在油封上和油封装配在轴上)弹簧的拉力转换得到,转换关系通过试验与仿真相结合的办法获得,最终实现了带簧油封2种状态下的径向力有限元计算。通过径向力测量仪验证计算结果的正确性,同时发现弹簧所产生的径向力并非百分之百转化为油封径向力。     

Analysis of contact force and thermal behaviour of lip seals

Using the Mooney-Rivlin model, the contact force and thermal behaviour of a radial lip seal are studied numerically and experimentally as a function of the interference. The numerical and experimental results on the static contact forces show good correspondence with and without the garter spring. The FEM calculated results indicate that increased interference may increase the eracking of seal material due to the maximum contact stresses close to the contacting area of the seal lip and produce local separation between the seal lip and the shaft. Also a coupled thermal-mechanical analysis method will be a useful tool to predict the contact behaviour of rubber lip seals for small values of the interference.     

Thermofluids Considerations and the Dynamic Behavior of a Finger Seal Assembly

Finger seals represent a compliant seal configuration. What differentiates and makes them preferable to the brush seals is their potential hydrodynamic lifting capabilities, and thus their noncontacting nature. The fingers' compliance allows both axial and radial adjustment to rotor excursions without damage to the integrity of the seal. The work to be presented here concerns the mapping of the thermofluid and dynamic behavior of a repetitive section of the newly proposed design of a two-layer finger seal. The assembly contains four high-pressure and four low-pressure fingers arranged axially in a staggered configuration and subject to an axial pressure drop. The numerical three-dimensional temperature and pressure results were obtained using a customized Navier-Stokes–based commercial package, CFD-ACE+. The results were obtained in a parametric fashion where the high-pressure side, the speed of rotation, and the heat transfer coefficient are the controlling parameters; the gas compressibility and the viscosity are also considered in the model of the thermofluids seal behavior. The stiffness and damping characteristics of the padded/unpadded fingers and the fluid were obtained through numerical simulation and were then used to model the interaction with the motion of the shaft. It is shown that the proposed geometry provides satisfactory lifting capability for the fingers. The fingers follow the motion of the shaft and their stiffness is small when compared to that of the fluid; thus, the displacement transmissibility is in most cases close to 1. Lifting forces and seal leakages, as well as the interaction between the profiled backplate and the low-pressure fingers through Coulomb damping/friction forces, are also parametrically studied.     

Modelling of a rotor-ball bearings system using Timoshenko beam and effects of rotating shaft on their dynamics

This study has focused on the influence of rotating shaft on the dynamics of rotor-ball bearings system. A mathematical modelling of the system has been carried out by considering shaft as rotating Timoshenko beam model. The radial force of rotor unbalance varied with rotating speed. The contact between balls and races is considered as nonlinear spring, whose stiffness is obtained by using Hertzian contact deformation theory. After the modelling for shaft, the governing equation of bearing are derived. The proposed mathematical model is validated experimentally. Moreover, the proposed model is also validated with previous published studies. The bifurcation diagram and Lyapunov exponent are presented to define the state of the system as a function of rotational speed. Fast Fourier transform (FFT) and phase trajectory are used to investigate the influence of the shaft under dynamics of the system.     

高速主轴离心膨胀及对轴承动态特性的影响

以高速主轴系统为对象,将主轴转子和轴承内圈分别等效为等截面梁和空心圆盘,计算离心力作用下主轴转子和轴承内圈的径向弹性变形,并分析主轴转子与轴承连接状态随转速升高的变化趋势。考虑旋转部件的离心膨胀变形,建立高速主轴轴承动力学模型并进行试验验证。在此基础上,研究离心效应对主轴轴承径向预紧状态的影响,揭示高速主轴轴承动态特性随转速的变化规律。研究结果表明,离心力引起的径向膨胀变形使滚动体与轴承内、外圈之间的接触角减小,接触力增加。主轴轴承的轴向刚度和径向刚度均随转速的升高而降低。轴承内圈的离心膨胀变形对轴承轴向刚度的影响可以忽略不计,而能在一定程度上提高轴承的径向刚度。     

A Transient Dynamic Analysis of Mechanical Seals Including Asperity Contact and Face Deformation

Face seals are typically designed to be in contact at standstill. However, as speed and pressure build up, the seal faces deform from their factory flat conditions because of viscous and dry friction heating, as well as mechanical and centrifugal effects. It is imperative that such deformations form a converging gap for radial flow to ensure stable operation and to promote favorable dynamic tracking between stator and rotor. A numerical simulation is presented for the transient response of a face seal that is subjected to forcing misalignments while speeds and pressures are ramped up and down. Asperity contact forces and transient face deformation caused by viscous heating are included. A new closed-form solution is obtained for the elastoplastic contact model, which allows seamless transition between contacting and noncontacting modes of operation. The model is then used to calculate face contact forces that occur predominantly during startup and shutdown. The viscous heating model shows that the time-dependent deformation (coning) is hereditary and that it lags behind the instantaneous heat generation. The dynamic analysis provides a numerical solution for the seal motion in axial and angular modes. The eventual build up of hydrostatic pressure and coning during startup generates opening forces and moments that separate the seal faces, resulting in noncontacting operation. The reverse occurs during shutdown; however, because of the thermal time constant a seal may continue to leak even after it returns to standstill. The analysis and simulation results compare very well with a closed-form solution that predicts a critical speed of separation of contacting seals.     

不同活塞杆用密封件应力松弛现象研究

该文利用广州机械科学研究院有限公司自有的油封径向力测试仪以及定制加工的轴套对Y圈,轴用方形圈,轴用阶梯圈以及V组等4种不同类型的活塞杆用橡塑密封件在特定温度下以及在宽温域下的应力松弛现象进行了研究。结果表明,随着温度的升高以及时间的推移,4种同一轴径、不同材料、不同结构形式的活塞杆用密封件均出现了应力松弛的现象,且不同密封件,其径向力初始值以及应力松弛的规律不同。     

气门油封结构参数设计及优化

为研究发动机气门油封结构参数对油封密封性能的影响,在有限元分析基础上,对油面唇角、气面唇角、安装过盈、唇口圆角半径、弹簧刚度等结构参数进行正交试验设计,研究油封结构参数对气门油封唇口最大接触压力和单位周长径向力的影响;以最大接触压力和最小单位周长径向力为优化目标,获取气门油封最优参数组合。研究结果表明:油封唇口圆角半径对油封唇口最大接触压力和单位周长径向力的影响程度都为最大;气面唇角对单位周长径向力有较显著的影响;油面唇角对油封唇口最大接触压力有较强的影响,但对单位周长径向力影响较小;弹簧刚度对单位周长径向力和最大接触压力影响均较小。结合均值最优水平分析,获得满足优化目标的油封参数组合,优化后油封比初始油封最大接触压力提升了85.61%,单位周长径向力降低了20.54%,在保证油封密封性的前提下,大大改善了油封唇口的磨损情况,提高了油封的使用寿命。     

Design considerations towards the construction of hybrid floating brush seal (HFBS)

The hybrid floating brush seal (HFBS) represents an advance in brush seal technology by combining brush seal and film riding face seal technologies to create a hybrid seal that allows both axial and radial excursions of the sealed shaft without damage to seal integrity. At the same time, it eliminates interface surface speeds between the rotor and the brush bristles. This accomplishment is possible because the brush seal, which forms the primary seal, rotates with the shaft, while floating against a hydrodynamic face seal surface, which makes up the secondary seal. The present paper presents continuation work (Int J of Rotating Machinery, 7, 2002) and will concentrate on the methodology of (i) designing and choosing brush characteristics, and (ii) the design of the face seal that allows the floating of the brush plates against it. The brush simplified analytical model predicts the effects of centrifugal force on the bristles and allows implementation of a methodology for choosing and optimizing bristle geometry. The face seal design concentrates on ensuring seal integrity and dynamic stability of the entire assembly.     

对阀杆填料密封问题的探讨

经过对阀杆填料密封时力的分析，得出填料的径向压力沿轴向方向的分布规律，并进一步分析了影响阀杆填料密封的主要因素。     

Light and short arc rubs in rotating machines: Experimental tests and modelling

Rotor-to-stator rub is a non-linear phenomenon which has been analyzed many times in rotordynamics literature, but very often these studies are devoted simply to highlight non-linearities, using very simple rotors, rather than to present reliable models. However, rotor-to-stator rub is actually one of the most common faults during the operation of rotating machinery. The frequency of its occurrence is increasing due to the trend of reducing the radial clearance between the seal and the rotor in modern turbine units, pumps and compressors in order to increase efficiency. Often the rub occurs between rotor and seals and the analysis of the phenomenon cannot set aside the consideration of the different relative stiffness. This paper presents some experimental results obtained by means of a test rig in which rub conditions of real machines are reproduced. In particular short arc rubs are considered and the shaft is stiffer than the obstacle. Then a model, suitable to be employed for real rotating machinery, is presented and the simulations obtained are compared with the experimental results. The model is able to reproduce the behaviour of the test rig.     

Performance evaluation of high pressure sleeve seal

Sealing problems for reciprocating pumps or intensifiers operating at high pressures (above 100 MPa) may be solved by adopting a closely fitting externally pressurized sleeve. This paper presents an elastohydrodynamic (EHD) analysis for such high pressure sleeve type seals and examines the effects of structural and operational parameters on their high pressure performance characteristics. The effects of pressure on the viscosity and density of the working fluid are also considered in the analysis. The numerical results clearly indicate that the sealing efficiency of high pressure sleeve seals can be enhanced with elastic deformation of both the sleeve and the plunger. The effect of working pressure on the stiffness of the sleeve seal and the induced frictional force are also presented. The study of the effect of eccentricity on the radial stiffness shows that it leads to a large radial force and the plunger is pressed on the sleeve surface, hereby termed ‘hydraulic locking’. This phenomenon results in an increase in frictional forces which is one of the key factors for the limited working life of the seal.     

偏心及部分进汽下密封间隙流体激振力数值研究

喷嘴配汽汽轮机在部分进汽时调节级附近会形成极不均匀的流场,不仅影响调节级动叶轮周力的分布,还会对临近密封间隙内的流场及流体对转子的作用力产生扰动。以某国产300MW汽轮机端部汽封间隙为参考,建立密封间隙CFD模型,求解三维、粘性、可压缩N-S方程,研究了不同进汽方式、偏心情况下流场特性及流体对转子作用力。结果表明:部分进汽的位置、转子的偏心距及两者的相对位置对汽流力的大小、方向和变化趋势产生了较大的影响。在某些部分进汽情况下,偏心距增大也会减小汽流力。     

斜直深槽机械密封环端面变形研究

深槽密封是通过力变形和热变形在密封面形成周向的波度和径向的锥度,从而产生热流体动力楔效应。通过热平衡分析和模型简化,应用有限元软件建立斜直深槽机械密封有限元分析模型,并对密封环温度场、力热变形进行求解,获得斜直深槽密封环的温度分布规律以及热变形规律。分析结果表明:斜直深槽密封端面结构产生的变形,能够形成周向波度和径向锥度,能够产生一定的流体动压效应,但规则波形的产生同流体槽的结构参数有关,需针对具体的工况参数进行相应的优化设计,方能达到所需要的流体动压效果。     

具有圆度误差的径向金属密封接触应力研究

由于加工圆度误差的影响,井下流量控制阀径向金属密封接触应力分布不均匀,从而影响密封性能。利用有限元方法研究具有圆度误差的径向金属密封唇部接触应力分布,并分析圆度误差对径向金属密封接触应力的影响;基于有限元分析结果提出径向金属密封接触应力分布的理论解析式,并进行误差分析。具有圆度误差的径向金属密封唇部接触应力分布的理论解与数值解相符,各参数引起的最大接触应力的平均相对误差约为10%。根据具有圆度误差的径向金属密封副接触应力的分布规律,提出合理的过盈量函数,修正了径向金属密封轴对称结构的悬臂梁模型的接触应力理论关系式,得出了圆度误差下的径向金属密封接触应力分布规律。研究结果为井下流量控制阀径向金属密封的设计提供了理论指导。     

Analysis of flow field around a ribbed helix lip seal

In this study, a direct numerical simulation model has been developed to elucidate the pumping mechanism of a radial lip seal with helical ribs. The flow field around the contact region between the seal lip and the shaft surface in the environment of a pumping-rate test rig, where both air and oil sides are filled with oil initially, was simulated. The streamline pattern and pressure field around the seal lip were examined. Complicate three-dimensional streamline topology was depicted. On the air side, high pressures built up on the windward faces of ribbed helices next to the lip helping to pump oil back to the sump. The vortex generated next to the lip on the oil side rotates such to create an inward pumping effect too. The pumping rates were calculated at shaft speeds, ranging from 2000 to 6000 rpm, and compared to the measured values from the test rig. Good agreement was observed. Both calculated and measured pumping rates increase as the shaft speed increases. The current results demonstrate the promising application of CFD in the design of radial lip seals.     

轮胎稳态运动学与六分力预报Ⅰ:理论与方法

提出一种新的轮胎运动学描述和六分力预报理论。滚动接触是汽车轮胎力学、轮轨动力学的核心问题,由于涉及刚体转动与有限变形,滚动接触运动学与动力学的描述与求解非常困难。用拉格朗日—欧拉混合描述法分析大变形滚动接触结构的速度场、加速度场和接触变形。以车轮定位角为卡尔丹角,用拉格朗日描述,得到了包含刚体转动和弹性变形的轮胎速度场。而接触区域的变形和受力用欧拉描述,通过欧拉网格和拉格朗日网格的信息传递,完成滚动结构动力学分析。所提出的理论可以退化到Fiala模型,并可以从理论上解释子午线轮胎的伪侧偏和伪侧倾现象。基于所建立的运动学理论和非线性有限元,建立轮胎六分力预报方法。针对某轿车子午线轮胎,分析轮胎接地面滑移速度、接地面积、接地压力、侧向剪力分布等随着侧偏角的变化规律,并研究该轮胎侧偏力和回正力矩随着胎面刚度和摩擦因数的参数敏感性。结果表明轮胎侧偏刚度和回正刚度主要受结构刚度控制,而峰值侧偏力和峰值回正力矩主要受摩擦因数控制。将利用所建立的方法和试验,探讨带束层结构对大规格子午线轮胎侧偏特性的影响规律,进一步验证所提出的理论和方法的正确性。所提出的理论和方法开辟了直接从轮胎设计预报轮胎六分力的新途径。     

非驱动轮毂轴承单元法兰盘轴颈静强度计算及试验

针对轮毂单元静强度计算及试验验证问题,根据第三代非驱动轮毂轴承单元的受力情况,提供了一种用CAE仿真分析方法以外的简便数值分析计算方法,即在车辆受到侧向1.2 g的临界侧向加速度下,将轮毂轴承单元受到的外部径向力和轴向力,通过轮毂轴承单元内部受力分析,转化为轴承内部双列滚道的两个载荷中心的径向力和轴向力;并将轮毂轴承单元法兰盘内侧受力轴颈简化等效为实心悬臂梁的处理方法,来计算法兰盘轴颈静强度;并用侧向静强度试验方法,通过构建适当的试验方案,来验证轮毂轴承单元法兰盘静强度,为设计优化提供简便的分析验证方法。研究结果表明,该简化模型计算结果能够与侧向静强度试验结果保持一致,为笔者利用简化计算方法来简便快速地定量选取轴径和轴颈r角大小提供了可能;该方法计算简便有效,结果可靠。     

压缩机径向泄漏通道润滑油量的实验研究

在压缩机运行过程中,通过径向泄漏通道从压缩腔泄漏到吸气腔的气体泄漏量与堆积在该处的润滑油量有极大的关系,为了准确描述径向间隙处的润滑油量,以滚动活塞压缩机本体为基础设计一套试验装置,采用高速摄影技术对径向间隙处的润滑油进行观察和图像采集,将采集的图像导入MatLab进行图像处理,得到滚动活塞压缩机在运行过程中的径向间隙处的润滑油量。以润滑油密封角为衡量润滑油量大小的指标,分析润滑油密封角与偏心轴转速、供油量、润滑油黏度的关系。结果表明:以汽缸中心点和活塞与汽缸的理论接触点的连线作为分界线,润滑油并不以该分界线作为对称中心均匀地分布在吸气腔和压缩腔两侧,而是整体偏向压缩腔侧,并且该分布规律与润滑油黏度、偏心轴转速和供油量都无关;润滑油密封角随着转速的提高而增大,随着供油量的增大而增大,随润滑油黏度的增加而减小。