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.     

螺旋槽端面密封脱开转速的理论及试验

提出螺旋槽端面密封脱开转速的理论分析模型,并建立适合于密封端面脱开后的内外双槽结构的非接触式端面密封数学模型。理论研究一种外螺旋槽和内人字槽组合的双螺旋槽端面密封的临界脱开转速,同时讨论该类非接触端面密封开启力、流量、摩擦力矩等随转速和密封间隙的变化规律。试验得到了直径100 mm、槽深3 μm的组合螺旋槽(外螺旋槽和内人字槽组合)端面密封在水介质(27 ℃)工况下的临界脱开转速,并将其与理论结果进行对比研究。研究结果表明,当密封转速超过约9 kr/min后,密封处在非接触状态,此时的密封泄漏量仅为1.2 mL/s。试验得到的端面密封脱开转速与理论结果一致(误差小于10%),从而有效地证实了端面脱开转速可作为对密封端面接触与否的判定依据。当密封转速高于脱开转速后,密封处在非接触状态,其工作寿命较长,泄漏量较小,这对于可重复使用火箭发动机涡轮泵端面密封的研制具有重要理论和试验参考价值。     

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。     

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.     

Experimental Investigations and Field Applications of Oil-Film-Lubricated Mechanical Face Seals with Spiral Grooves

The oil-film-lubricated mechanical face seal described here is a hydrodynamically lubricated, noncontacting, mechanical face seal with zero leakage. On the basis of systematic theoretical analyses, research on design methods, and experimental investigations, many field applications have been made. The experimental investigations include test rig development; long-time high-speed running tests; frequent start-up and shut-down tests; measurements of the seal leakage, face temperature, and characteristics of the self-circulating screw pump; observation, measurement, and solution of interface wear, and so on. Until now, this new seal design has been successfully applied in more than 40 high-speed turbocompressors in the oil refinery and petrochemical industries, achieving zero leakage and long operation. These seals are all designed with different face spiral-groove patterns, structure arrangements, and supporting systems.     

"零压差零泄漏"液体润滑螺旋槽机械密封性能的实验研究

通过实验方法,研究了内外双螺旋槽机械密封端面简的液膜压力和端面温升。液膜压力直接反映了密封端面的润滑状况,液膜压力开始随转速的增加而增大,当转速较大时,随转速的再增大而下降。正常运转时,端面温升很小。实验研究表明,螺旋槽机械密封能在保持零泄漏的同时,实现端面的非接触。     

螺旋槽上游泵送机械密封摩擦系数的解析分析

上游泵送机械密封是一种具有环保、长寿命、低能耗的高新密封技术,其应用前景将十分广阔。端面液膜特性是决定上游泵送机械密封工作寿命和密封性能好坏的关键因素。主要依据流体雷诺方程和Muijderman无限窄槽理论,再用端面槽型因子对其进行修正,推导了螺旋槽上游泵送机械密封端面间液膜的径向压力分布、泄漏率、承载力、摩擦力、摩擦系数等液膜特性参数的计算公式,并重点分析了操作参数与槽型参数对端面摩擦系数的影响。研究表明,摩擦系数随转速和粘度增加而增加,随压力增加而减小。槽深H'=2.5、槽数Ng=10~18、槽宽比B=0.6~0.8、槽长比l=0.6~0.7时,密封环端面间摩擦系数较小,液膜特性较好,这时端面间间隙对摩擦系数几乎没有影响。此研究结果可为上游泵送机械密封的正确使用和设计提供依据。     

基于Fluent的螺旋槽上游泵送机械密封三维微间隙流场数值模拟

密封端面微间隙液膜特性是上游泵送机械密封性能研究的关键。采用Pro/E wildfire软件建立参数化螺旋槽上游泵送机械密封端面微间隙液膜几何模型,以清水为工作介质,使用Fluent软件,对跨尺度密封端面微间隙流场进行三维数值模拟,得到开启力及压力分布规律,并与有关测试结果进行对比分析,实验数据与模拟数值基本吻合,表明所采用的模拟方案可对螺旋槽上游泵送机械密封微间隙三维流场进行较好地描述,该方法可用于密封端面微间隙流场及性能的系统研究;对端面压强分布进行分析,结果表明,在螺旋槽外槽根处存在最大静压,液膜开启力的增大主要来源于槽根产生的最大静压。     

Design and Experimental Study on the Controllable High-Speed Spiral Groove Face Seals

The spiral groove face seal is a prime candidate for application of the liquid oxygen and liquid hydrogen turbopump. The study investigated the designs of the electro-magnetic loading device (EMLD) and friction torque testing device (FTTD), and their application in the interface experiments of face seals with spiral grooves which used water as the sealing fluid. The seal performance parameters, including face temperature, face friction torque, film pressure at the seal dam, were measured under the static balance position, and the effects of the face closing force, which varied with the axial load generated from the EMLD, on the seal performance were tested under a specific controlled mode. The result indicated that both the pressure at the seal dam and face temperature increased with the rotating speed and that small friction was obtained when the face seal was fully film-lubricated. The separation speed of the controllable seal could also be controlled, which helped seal faces lift off and met the conditions of the face noncontact status. Additionally, with the application of the EMLD and FTTD, seal operation monitoring was rendered possible and a controllable face seal with desirable performance was achieved. The findings of the current study lend great insights into engineering seal design and its applications.     

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.     

Effect of Axially Grooved Oil Seals on the Leakage Flow and Stability of a Centrifugal Compressor

The results of an analytical investigation are given for the effect of axially grooved floating oil ring seals on the leakage flow and stability of a centrifugal gas compressor. The finite element method was used to solve the non-linear and coupled hydrodynamic and thermal equations for pressure and temperature distributions in the oil seal ring with and without the axial grooves. The peturbation technique was used to obtain the static and dynamic characteristics of the oil seal. The results for selected cases of axial grooving are presented in graphical form for operation at various eccentricities. The non-dimensional leakage flow results correlate well with previously published results calculated by narrow groove theory. The stability of a multi-stage gas compressor is evaluated for different configurations of the oil seal grooving geometry. The compressor rotor shaft finite element model includes a multi-level analysis for the oil seal rings that permits the evaluation of the floating seal influence on the total system stability. Results are given for both low and high-pressure sealing conditions, which simulate test stand and field operating conditions. The results show that the added grooves enhance the stable operation of the rotor system for low-pressure fixed seal conditions arid reduce the system stability at lower eccentricities for low-pressure floating seal conditions. In high pressure conditions the added grooves enhance the stability of the system for both fixed and floating seal conditions.     

螺旋槽-波锥坝组合型非接触式机械密封性能分析

针对液体润滑非接触式机械密封在低黏环境下承载性能不足的问题,提出一种新型螺旋槽-波锥坝动静压组合型机械密封结构,采用MATLAB软件利用有限差分法求解考虑质量守恒空化边界的雷诺方程,并将组合槽与螺旋槽、波锥坝的密封性能进行比较,进一步分析不同结构参数与工况参数对组合槽性能参数的影响规律。结果表明:新槽型波数与螺旋槽数重合时组合密封在径向出现2个压力峰值,相较于单一槽型结构拥有更好的承载能力与较小的摩擦扭矩;液膜力与泄漏量随波锥比或径向宽度比的增加而增大,外径压力和转速越大,组合槽的承载性能提升越显著,但外径压力的升高会造成较大的径向泄漏。组合槽结合了波锥槽的静压承载与螺旋槽的动压承载综合优势,将有效提升液体润滑非接触式机械密封在低黏环境下的润滑性能。     

双槽阶梯槽干气密封性能研究

针对干气密封系统在高转速工况下密封性能差、泄漏量大的问题,提出一种双槽阶梯槽端面密封结构.采用CFD对比分析不同压力、转速下单螺旋槽、双槽阶梯槽、阶梯槽3种槽型的密封性能,探讨槽深、螺旋角对密封性能的影响,得出了双槽阶梯槽型优化的结构参数.结果表明:双槽阶梯槽在降低泄漏量和提高综合密封性能上要优于阶梯槽和单螺旋槽;在槽...     

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。     

阶梯收敛槽机械密封空化效应及密封性能优化分析

为解决波度端面机械密封精密加工困难的问题,基于收敛型槽具有较低的泄漏量和较高的流体静压效应的特点,提出一种由波度端面机械密封结构衍生变化的阶梯收敛槽机械密封结构,考虑空化作用,对不同结构参数及工况参数下机械密封密封性能进行CFD流体仿真分析。结果表明：工况参数及结构参数对液膜空化效应有显著的影响,其中随着膜厚、密封压力以及槽深的增加,液膜空化效应均减弱,随着转速的增大,液膜空化效应变强。以开漏比评价密封性能,结果表明,阶梯收敛槽机械密封在小膜厚、高转速、较低密封压力以及较小静环开槽深度下运行时可获得最优密封性能;但为保证密封端面液膜具有足够的承载力,开槽深度不宜过小。     

A Model for Mechanical Seals with Regular Microsurface Structure

A mathematical model is developed to allow performance prediction of all-liquid noncontacting mechanical seals with regular microsurface structure in the form of hemispherical pores. Seal performance such as the equilibrium face separation, friction torque and leakage across the seal are calculated and presented for a range of sealed pressure, pore size and pore ratio of ring surface area. An optimum pore size is found that depends on the other variables and corresponds to maximum axial stiffness and minimum friction torque. Also, a critical pore size is found above which seal failure is possible.     

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。     

机械密封的功率消耗试验及测量方法

随着机械密封应用的普及、机械密封的失效已成为石油化工等部门的回转机械（离心泵等）工作不可靠的重要因素,机械密封的端面摩擦不但直接消耗能源,而且,因端面摩擦过度而引起的密封失效泄漏所造成的损失则更大。本文在试验的基础上,研究了机械密封消耗的构成,介绍机械密封摩擦功率的测量方法,对机械密封不同工况不功率消耗的变化进行了分析,提出了降低机械密封功率消耗和改善密封功能,提高机械密封的工作可靠性的途径。     

On the Dynamic Behavior of Two Gas-Lubricated Two-Lobe Journal Bearing Configurations

A Finite Element model for the noncontacting gas face seal is developed based on the modified Reynolds Equation developed by Fukui and Kaneko (4), (5) that considers the slip flow effects. Numerical studies of a representative spiral groove seal at the slow speed (≤, 500 rpm) and the low pressure (≤ .303 MPa) conditions showed that slip flow can significantly affect the seal performances such as the lift-off speed, leakage rate, load carrying capacities. Without the consideration of the slip flow effect, the lift-off speed and the corresponding leakage rate would be greatly underestimated, especially at near ambient pressure condition. By examining the F-h characteristic curves, it was found that under the parameters presented in the present study the slip flow could be significant for Knudsen number, Kn as small as .05, and the slip flow in effect reduces the viscous pumping resulting in a loss of load carrying capacities.     

内圆弧槽机械密封液膜流场特性分析

以内圆弧槽流体动压型机械密封为研究对象,建立了动静环端面间液膜的三维模型,运用计算流体动力学理论和有限体积法对端面间液膜的流场特性和装置的密封性能进行了模拟和数值分析。对处于不同工况、不同密封介质条件下的液膜流场,得到了其压力、泄漏量、开启力和摩擦扭矩的变化规律及相互影响关系。结果表明:圆弧槽能够产生明显的动压效应,动压效应的大小与动环转速呈正比;液膜的压力沿径向由内径到外径逐次降低;泄露量的大小随动环转速或介质压力的增大而增大;开启力的大小与动环端面的总压力具有相似的变化规律。