Shaoxian Bai

Thermoelastohydrodynamic Behavior of Gas Spiral Groove Face Seals Operating at High Pressure and Speed

A numerical modeling of thermoelastohydrodynamic gas spiral groove face seal behavior is presented. Temperature fields of the fluid film and the seal rings are computed, as they are the elastic and thermal distortions of the rings. Numerical analysis is carried out on a gas spiral groove face seal taking into account of choked flow effect. Analysis results show that both elastic and thermal distortions induce strong influence on the geometry of the fluid film, forming obvious divergent clearance which leads to significant decrease of minimum equilibrium clearance, exceeding 50% in degree. Thermal distortion may induce the same influence degree as elastic distortion on the minimum equilibrium clearance in high pressure cases, but the rotation speed has no obvious influence on the minimum clearance when both elastic and thermal distortions are considered. The thermal distortion as well as elastic distortion should be concerned in high pressure analysis.

Frictional Performance of a Textured Surface with Elliptical Dimples: Geometric and Distribution Effects

Geometric and distribution effects of inclined dimples on the friction and wear performance of a textured surface were experimentally investigated. The frictional coefficients and face temperatures of four different kinds of elliptical surfaces were measured under various conditions of rotation speed, load, and viscosity. Experimental results showed that distribution parameters significantly affected frictional performance. From the experiments it was found that surfaces with double-row elliptical dimples have smaller frictional coefficients and lower face temperatures than that of the single-row elliptical dimples and had a 59% decrease in frictional coefficient and a 58% decrease in face temperature rise. This means that double-row elliptical dimples can lead to a more profound hydrodynamic effect as well as possess a lower chance of surface contact and wear. Moreover, a larger dimple diameter and slender ratio further improved the frictional performance of the textured surface with double-row elliptical dimples.

Modeling of Gas Thermal Effect Based on Energy Equipartition Principle

In the present article, a gas thermal effect is modeled based on the energy equipartition principle. Two new independent state equations for an ideal gas are developed that provide a new way to analyze thermal effects in gas lubrication. Furthermore, the energy equation is derived for gas lubrication and the analysis of thermal effects is carried out on a gas spiral thrust bearing and a gas hydrostatic journal bearing. The results show that gas temperature increases significantly in the lubricated region at high speed for both the thrust and hydrostatic journal bearings, and the thermal effect positively influences the load capacity of the thrust bearing. The gas expansion effect makes the gas temperature decrease in the hydrostatic journal bearing, and the gas temperature decreases with an increase in the inlet pressure.

Pseudo-Nine-Point Finite Difference Method for Numerical Analysis of Lubrication

Contours of surface texture of contact faces are not always parallel to the directions of the axis in solving Reynolds equations with finite difference method, and this often induces significant pressure saw-tooth effect, which results in an unignored analysis error. In this paper, pseudo-nine-point finite difference, as a new finite difference method, is introduced to solve the lubrication numerical problem of pressure saw-tooth. Also, application is carried out in gas lubrication of hard disk systems to verify the validity of the new method. In analysis, pressure distributions and gas floating forces are calculated for two different types of sliders, and the astringency and efficiency of the new method is discussed. Numerical results show that the pseudo-nine-point finite difference method can restrain pressure saw-tooth evidently, and presents better astringency and efficiency than the traditional five-point finite difference method. With the increase in mesh density, pressure distribution and gas floating force trend to steady. Also, numerical values of the floating force agree well with the experimental ones.

Experimental Investigation of an Inclined Ellipse Dimpled Gas Face Seal

An inclined elliptical dimpled gas face seal was experimentally investigated in order to provide evidence for theoretical study. An experimental setup and theoretical model were developed to study the hydrodynamic effect of this gas seal. Then, opening and steady performance of the seal was measured under different rotational speed and seal pressure. The clearance and leakage rate are discussed for different cases of pressure and rotational speed. The results showed that there was a good correlation between theory and experiment. Both the clearance and the leakage rate increased significantly with increasing rotational speed and seal pressure. The inclined elliptical dimpled gas face seal was a type of hydrodynamic seal.

Thermoelastohydrodynamic Gas Lubrication of Spiral-Groove Face Seals: Modeling and Analysis of Vapor Condensation

ABSTRACT Vapor condensation in gas lubrication of high-pressure spiral-groove face seals is analyzed in this article. A mathematical model of vapor condensation elastohydrodynamic lubrication (EHL) is developed taking into account gas humidity and thermoelastic deformation of seal rings. Vapor condensation is numerically predicted at high speed and pressure. It is found that vapor condensation usually occurs in the sealing dam region, where the lubrication state changes from gas lubrication to gas–liquid lubrication. The vapor condensation rate increases with an increase in humidity and seal pressure. Under high-pressure conditions, seal clearance has a significant influence on the vapor condensing rate but the rotational speed does not.