螺旋槽干气密封稳态特性分析模型的对比研究

干气密封的稳态特性是密封设计中的重要依据和指标。干气密封稳态特性可通过基于轴向力平衡的静态模型和轴向-角向耦合的动态模型两种途径获得。基于上述两种模型间存在的差异点,就动环偏摆角、静环静态偏摆角和副密封阻尼展开参数研究,讨论两种模型计算所得的稳态特性（膜厚与泄漏率）之间存在的差异,进而给出它们在干气密封稳态特性研究中的适用性分析。计算中,动力学方程和流场方程分别采用有限差分法和有限元法进行离散求解,以膜厚与泄漏量为稳态特性的主要指标。结果表明,当副密封阻尼较小时,角向偏摆角对于静环稳态特性的影响极小,可用静态模型来近似动态模型,以简化计算过程和缩短计算时间。而当副密封阻尼较大时,密封动静环的角向相位差较大,显著地影响密封静环的稳态特性,使用静态模型获得的结果与动态模型的结果差别较大,而且此时前者无法反映由于静环角向追随性较差引起两环端面易发生接触的问题,因此大阻尼情况下宜采用动态模型。     

波度及静环静态角偏差对螺旋槽气体端面密封稳态特性的影响

建立了考虑螺旋槽气体密封端面周向波度及静环静态角偏差的理论模型。利用有限元法数值求解稳态雷诺方程,得到了端面周向气膜压力分布,进一步分析了不同压缩数下周向波度及静环静态角偏差对密封稳态特性参数的影响规律。结果表明:中、高压缩数下,波度及静环静态角偏差对气膜周向压力分布及径向压力梯度产生显著影响;波幅及波数对密封稳态特性影响不尽相同;过大的静环静态角偏差会导致端面气膜压力出现不均匀的峰值及谷值,使密封产生剧烈偏摆,造成端面瞬间接触,加剧端面磨损,最终导致密封泄漏失效。     

机械密封浮动环处O形密封圈动态刚度和阻尼的测量

利用INSTRON高频疲劳试验机对O形辅助密封圈进行松弛试验,获得气体和水润滑2种状态下O形辅助密封圈载荷随时间的变化曲线,通过数据处理获得其轴向动态刚度和阻尼,根据经验公式进一步确定其角向刚度和阻尼。分析O形辅助密封圈在气体和水润滑下动态刚度和阻尼随着加载频率、位移、转速的变化规律。结果表明:在气体和水润滑下,在一定范围内辅助密封圈的动态刚度和阻尼值随加载频率的升高而增大;在水润滑状态下,随着加载位移量的增大,辅助密封圈的动态刚度和阻尼值逐渐变小;在气体和水润滑下,都存在一转速临界值,在临界值之前,随转速的增加,轴向动态刚度增大,轴向动态阻尼减小;在临界值之后,轴向动态刚度和阻尼值不再变化,稳定在某一值。     

油气两相动压密封自振稳定性流固热耦合分析

考虑热与变形对油气两相动压密封自振稳定性的影响,建立基于油气两相动压密封自振稳定性数学模型,采用流固热耦合有限元方法,研究油气比、转速、压差和O形圈阻尼等参数对油气两相动压密封受干扰后的轴向、角向自振稳定性能的影响。结果表明:转速较低时轴向自振稳定性较好而角向自振稳定性较差,转速高时两者相反,O形圈阻尼较低时轴向自振稳定性较差而角向自振稳定性较好,O形圈阻尼高时两者相反,因此在极端转速和取极端O形圈阻尼的情况下轴向或角向临界频率较小,不利于油气两相动压密封自振稳定;压差越大轴向临界频率越大,轴向自振稳定性越好,但角向临界频率越小,角向自振稳定性越差;随着两相介质油气比的增大,轴向临界频率减小而轴向临界质量增大,油气比在0.1～0.15时临界频率、质量以及转动惯量较大,密封综合自振稳定性能较好。     

Application of Fractal Contact Model in Dynamic Performance Analysis of Gas Face Seals

Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.     

锥度对螺旋槽气体端面密封稳态特性的影响

提出一种考虑螺旋槽气体密封端面径向锥度的理论模型。利用有限元法求解密封端面间气膜控制方程——雷诺方程，得到了端面膜压分布。计算了密封稳态性能参数，并与有关文献值进行了比较。分析了端面锥度对密封稳态特性的影响，进一步预测了密封端面出现接触摩擦的临界锥度。结果表明，锥度改变了端面膜压分布，并显著影响开启力、气膜刚度以及泄漏率等参数；过度变形将会导致密封因端面接触或大量泄漏而失效。     

Gas film disturbance characteristics analysis of high-speed and high-pressure dry gas seal

The dry gas seal(DGS) has been widely used in high parameters centrifugal compressor, but the intense vibrations of shafting,especially in high-speed condition, usually result in DGS's failure. So the DGS's ability of resisting outside interference has become a determining factor of the further development of centrifugal compressor. However, the systematic researches of which about gas film disturbance characteristics of high parameters DGS are very little. In order to study gas film disturbance characteristics of high-speed and high-pressure spiral groove dry gas seal(S-DGS) with a flexibly mounted stator, rotor axial runout and misalignment are taken into consideration, and the finite difference method and analytical method are used to analyze the influence of gas film thickness disturbance on sealing performance parameters, what's more, the effects of many key factors on gas film thickness disturbance are systematically investigated. The results show that, when sealed pressure is 10.1MPa and seal face average linear velocity is 107.3 m/s, gas film thickness disturbance has a significant effect on leakage rate, but has relatively litter effect on open force; Excessively large excitation amplitude or excessively high excitation frequency can lead to severe gas film thickness disturbance; And it is beneficial to assure a smaller gas film thickness disturbance when the stator material density is between 3.1 g/cm~3 to 8.4 g/cm~3; Ensuring sealing performance while minimizing support axial stiffness and support axial damping can help to improve dynamic tracking property of dry gas seal. The proposed research provides the instruction to optimize dynamic tracking property of the DGS.     

Clearance Regulation of Mechanical Gas Face Seals: Part II—Analysis and Control

This article presents the analysis and control of noncontacting mechanical gas face seals based on the state space model developed in Part I. Methods to analyze the controllability and observability of axial and tilt modes are described. The controllability analysis determines to what extent the dynamic response of the seal system modes can be shaped in a closed-loop feedback system, and the observability analysis determines if the seal system modes can be reconstructed from specific state measurements of the axial clearance and stator tilts. The error state-space method is employed to design a tracking controller to regulate the seal at a prescribed axial clearance. The control law is a function of all axial states; therefore, reduced order linear observers are designed to observe the unmeasured axial and tilt seal states. The axial clearance and tilt state estimates are used to reconstruct the gas film axial force and moments, which cannot be directly measured, for design and analysis. The analysis and control techniques are applied to the illustrative example presented in Part I. The results demonstrate that the gas film forces and moments can be estimated well and the seal system can be satisfactorily regulated with a sufficiently damped response that is within the bandwidth of today's electropneumatic actuators.     

Parametric Study of Spiral Groove Gas Face Seals

A finite element analysis for the isothermal flow in spiral groove gas face seals is detailed along with a successive approximation method for the iterative solution of the nonlinear Reynolds equation. Zeroth- and first-order pressure fields are calculated for evaluation of the seal opening force and leakage and the axial stiffness and damping force coefficients, respectively. A parametric study shows the static and dynamic force behavior of a baseline SGFS operating with a large pressure ratio. The recommended geometric parameters presented ensure large static stiffness and damping force coefficients while still allowing for low seal leakage rates. A reduction in the power loss and a significant increase in the seal static stiffness coefficient are unique features of thin seal dams.     

螺旋槽气体润滑机械密封温度场有限元分析

应用有限元法计算了螺旋槽气体润滑机械密封的稳态温度场分布.计算了不同压力、转速及导热材料下密封环温度分布,并与实验值做以比较,并对计算结果进行分析.     

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.     

干式气体端面密封的研究现状

非接触式干式气体端面密封(DGS)是一种新型机械密封,在旋转机泵的转轴轴端密封装置中已经得到成功应用.对DGS的研究进展进行了总结,着重介绍了密封性能的理论分析与数值计算方法,端面微槽的优化设计方法,试验研究方法以及考虑端面微尺度效应和滑移流效应基础研究等方面的研究现状.指出在高参数条件下DGS端面的热流固耦合与解耦分析,低速或低压条件下密封的启动与停车性能的准确预测及结构优化是DGS技术未来研究的重点,也是进一步拓广DGS应用领域、提高其工作可靠性的关键.     

衍生螺旋槽对超临界二氧化碳干气密封微气膜稳态特性影响*

以衍生螺旋槽为研究对象,建立衍生螺旋槽端面微气膜三维流动模型,通过软件REFPROP获取CO2在不同压力温度下的物性参数,并导入Fluent计算得到了衍生螺旋槽和经典螺旋槽的膜压分布。对比分析衍生螺旋槽和经典螺旋槽S-CO2干气密封开启力、泄漏率和气膜刚度,讨论不同入口压力和转速下湍流效应、实际气体效应以及离心惯性力对密封稳态性能的影响,揭示多种效应交互耦合对S-CO2干气密封气膜动态特性的密封机制。结果表明：衍生螺旋槽的气膜开启力、泄漏率和气膜刚度等性能参数优于经典螺旋槽,这是衍生螺旋槽两级台阶作用的结果;随着转速的增加,在湍流效应和离心惯性力的交互耦合作用下,开启力、泄漏率及气膜刚度先增大后减小,随入口压力的增大,气膜开启力、泄漏率和气膜刚度均呈近似线性增大,且压力越大衍生螺旋槽和经典螺旋槽的差异越来越明显。     

新型组合槽端面干气密封特性研究

为了进一步提升干气密封端面流体膜动压效应,提出一种新型组合槽端面干气密封,该组合槽由两个相邻的螺旋槽周向部分重叠组合而成,包括一个长螺旋槽,一个短螺旋槽,两槽的槽深及径向长度不同。建立该组合槽与传统槽端面密封的数学模型,并运用有限差分法对其密封性能进行数值分析。结果表明:新型组合槽在端面间隙约小于1.5μm区域,流体膜开启力大于传统槽,且间隙越小,两者差值越大;泄漏量亦大于传统槽,但其值远小于泄漏量的设计值;在端面间隙约小于3.5μm区域,新型组合槽流体膜刚度显著大于传统槽,且间隙越小,两者差值越大。鉴于组合槽在泄漏量不超标的情况下,在间隙较小时端面流体膜具有更大的刚度、开启力及刚漏比,其综合性能显著优于传统槽型密封。     

Pressure dam influence on the performance of gas face seals

The introduction of grooves, micropores, and other forms of surface geometric modifications onto the mating seal plates has been performed to enhance the gas face seal performance. Reducing fluid leakage through the seal surface has been the main motivation for the development of efficient sealing technology for industrial turbomachinery. Pressure dams are generally etched on the seal inner and outer radii to improve even more the seal capability of reducing the gas leakage to atmosphere. This paper presents a finite element analysis carried out to determine the opening force, the flow leakage and the dynamic force coefficients of flat gas face seals with pressure dams operating under stringent conditions. Several curves of steady-state and dynamic seal performance characteristics depict the influence of the pressure dam position and width on the seal performance and efficiency.     

液体润滑分段螺旋槽端面密封性能分析

为探讨螺旋槽衍生槽型液体润滑端面密封性能,以中间开槽密封为研究对象,建立考虑质量守恒JFO空化边界条件的雷诺方程,采用有限差分法进行数值求解,对螺旋槽、二段槽以及三段槽的性能进行对比分析,探讨结构参数和操作参数对其泵送能力、动压承载能力以及空化情况的影响,计算域中槽区边界处的膜厚值采用调和平均处理。结果表明:在所给参数范围内,3种槽型的泵送率几乎均为正值,即均可实现上游泵送;三段槽的流体膜承载力受转速影响的程度明显小于另2种槽型;相同条件下三段槽更不易诱发空化,其次为二段槽;相比于螺旋槽和二段槽,三段槽受结构参数和操作参数的影响更小,具有更稳定的流体膜承载力及上游泵送性能。     

Automatic Feedback Control of Mechanical Gas Face Seals via Clearance Control

A new analytical approach is presented for designing controllers to regulate the axial clearance of a coned-face flexibly mounted stator mechanical gas face seal. The seal axial clearance is controlled by regulating the back-pressure force acting on the stator. The controllers are systematically designed using a completely analytical seal system model in which the linearized gas film stiffness and damping properties are represented by a constitutive model. An algorithm based on this model is derived to calculate the critical axial clearance where the seal is marginally stable, and a stable reference axial clearance is chosen. Proportional and proportional-plus-integral controllers are designed and analytically studied in terms of closed-loop stability and speed of response using the system model. The controllers are verified using a full numerical simulation (including nonlinear effects) of the mechanical gas face seal system, and the results demonstrate the effectiveness of both controllers to maintain the reference axial clearance.     

Dynamic Tracking of Angular Misalignment in Liquid-Lubricated End-Face Seals

End-face seals sometimes fail because the flexibly mounted face is unable to track the inevitable angular misalignment (relative to the shaft axis) of the fixed face, resulting in rubbing contact. It is important, then, that the critical amount of misalignment just to cause contact in a fully liquid-lubricated seal should be known so allowances can be made in the manufacturing and assembly tolerances.

An analysis of dynamic tracking is presented for both common end-face seal arrangements. Expressions for critical misalignment are derived in terms of inertia, elastomer stiffness and damping, and fluid-film hydrostatic and hydrodynamic moment effects in the diametral tilt mode.

Fluid-film effects are found to promote tracking, elastomer effects to resist. Tilt inertia resists tracking only for the flexibly mounted stator arrangement. However, as the inertia term is generally insignificant, this arrangement is preferred because, in practice, it is much easier to achieve good alignment of a rotating face fixed to the shaft than a stationary face fixed in a housing.     

Theoretical Analyses and Field Applications of Gas-Film Lubricated Mechanical Face Seals with Herringbone Spiral Grooves

The gas-film-lubricated mechanical face seal is a combined hydrodynamic and hydrostatic seal with positive leakage. Up to now, it has been widely accepted by end, users and builders of high-speed turbo compressors. The groove technology on the sealing face of the seat is one of the core technologies of dry gas seals. This article presents a patented herringbone spiral-grooved gas seal. Its one-dimensional analytical solution and two-dimensional numerical solution methods for the gas-film pressure distribution on the sealing face are presented. Up to now, more than 200 gas seals adopting this groove technology have been applied successfully in high-speed turbo compressors that deal with dangerous process gas in the oil refinery and petrochemical industries. The theoretical analyses and field applications show that gas seals with herringbone spiral grooves are advanced and practicable.     

智能往复密封件摩擦力检测装置的研制

Aiming at the problem of automatic detection of the friction of hydraulic reciprocating seals under the condition of high pressure and multi-cycle times,based on the detection principle of the starting friction and the dynamic friction of the reciprocating seals,a detecting system was designed,and the hardware configuration,PLC software design and man-machine interface design of the control system of the detecting device were done,the friction detecting device of reciprocating seals was eventually obtained based on PLC and kingview. The friction test of O-ring seals under the pressure of 25 MPa and recurring 1 000 times was done by the detecting device. The results indicate that the detecting device can detect the dynamic and starting friction of reciprocating seals under the complex condition of high pressure and achieve the test operation process and detection process in the man-machine interface,realize the detection accuracy of 0.65 N,the detection process is stable and reliable a high degree of automation and human-computer interaction. [ABSTRACT FROM AUTHOR]