In solving Reynolds equation with the conventional finite difference method, keeping the flow continuity has ofen been ignored, which will lead to an analysis error in the pressure distribution and leakage rate, especially for discontinuous clearance caused by step structures such as laser surface texturing sealing surfaces. In this paper, a finite difference method is introduced to satisfy the flow continuity to solve the Reynolds equation. Then, the pressure distribution for a typical rectangular step structure is obtained via two different methods: a numerical solution of the exact full Navier-Stokes equations, and a solution of the Reynolds equation solved by the previously mentioned method. A comparison between the two solution methods illustrates that, for both pressure flow and shear flow, the pressure distribution from the new difference method is in good agreement with that from the Navier-Stokes equations, and the new difference method can reflect the characteristic of the pressure sudden-change of the shear flow at the steps. Finally, the pressure distribution and leakage rate of a step-dimpled seal face are acquired with the presented method. The results show that the presented method allows gas-lubricating analysis of mechanical face seals with discontinuous clearance, and can keep the leakage rate continuous in the radial direction.

The hydrodynamic effect of a mechanical seal with directional multi-pores was studied by the zero-pressure-open experiments. Two kinds of different face structures with directional micropores onto their surfaces were studied. The film thickness and friction torque between the faces were measured at different speeds. The opening properties due to the hydrodynamic pressure of the gas film were analyzed. The results show that the directional micropores can increase opening force of such a gas face seal,and then to ensure the quick opening of the faces so that the face wear is avoided.

Laser surface texture (LST) can be used to enhance performance in hydrodynamic gas-lubricated mechanical seals. A mathematical model based on the solution of the Reynolds equation for the gas fluid is developed to study the influence of dimple orientation. Then, a parametric investigation of the texturing parameters such as dimple inclination angle, dimple depth, and dimple area rate are presented for the presented gas seal under different operating parameters of rotation speed, seal pressure, and seal clearance. Under the given operating conditions, the reasonable range of the structural parameters are given. A detailed dimensionless analysis of the texturing parameters is performed to achieve maximum gas film stiffness with minimum gas leakage.

A new type of hydrodynamic laser surface texturing gas seal with orientation ellipse dimples is introduced to improve hydrodynamic effect. Theoretical model is developed to study the hydrodynamic effect of this new gas seal. Then, a parametric investigation of the texturing parameters such as slender ratio, dimple inclination angle, dimple depth, and dimple area rate is presented for the presented gas seal under different operating parameters of rotation speed, seal pressure, and clearance. Results show that the orientation dimples can greatly improve hydrodynamic effect of laser surface texturing gas seals. Open force may be improved more than 20% greater by hydrodynamic effect in the analysis.