The Influence Of Surface Topography Of Hydrodynamic Groove On Sealing Performance Of Dry Gas Seal At Mid-low Speed

Under the mid-low speed condition,the existing problem of inadequate lubrication and unstable operation will cause friction and wear for face-to-face contact,which will affect the normal operation of gas seal and reduce its service life.Rational design of surface topography can bring about obvious hydrodynamic effect,which can improve the lubrication condition of gas seal.in order to further improve gas-film bearing characteristics and stability at mid-low speed,the theory and numerical analysis of surface-topography effect was conducted for spiral groove dry gas seal.First,considering the effect of groove surface topography on fluid lubrication characteristics,the modified lubrication model was established based on gas lubrication theories,then finite difference method was used for numerical analysis of mathematical model.Secondly,according to the modified lubrication model,the flow factors of rough surface was discussed by analyzing the effect of topography parameters and film thickness ratio on flow factors.The properties of gas film between seal face under shearing condition and pressure-driven condition was analyzed by analyzing the effect of operating parameters on gas velocity distribution and pressure distribution.Thirdly,considering the effect of surface roughness orientation on the lubrication condition,the sealing performance of spiral groove gas seal was analyzed.The discussion about bearing capacity and stiffness under different topography parameters,operating parameters and configuration parameters aimed at typical ?r=-45°,?r=45° surface and isotropic surface was conducted.therefore,the degree and the incidence of roughness-orientation effect on sealing performance under different conditions can be gained systematically.Finally,based on the objective function of gas-film bearing capacity and stiffness,the synergy between surface topography and groove was discussed,and,the variation of surface-topography effect with varing operating parameters was analyzed,then,the surface topography applicable to certain operating parameters and configuration parameters was gained.Meanwhile,the pattern spectrum of orientation angle was provided.so,the preliminary optimization of surface topography applicable to low-speed gas seal was achieved.Results showed that striated roughness whose orientation is closely parallel to the flow direction in groove can cause a good gas-film bearing capacity and stability for it can produce extra fluid dynamic pressure effect.The effect of striated roughness is more obvious under the condition of low pressure,small seal clearance,small groove depth and high speed.And it has a great influence on stiffness while causes little impact to bearing force.There's quite obviously a lot of synergy between groove and surface topography,In aspect of height,the larger the groove depth,the more obvious the synergy effect.In aspect of orientation,synergy effect remain unchanged at different spiral angle.In optimization,the pattern spectrum of orientation angle was gained with the change of pressure and speed.Under the condition of low pressure and high speed,it's rational to optimize surface topography by bearing capacity and stiffness.With the increase of speed and the decrease of pressure,the angle of striated roughness decreased.Under the condition of high pressure and low speed,it's rational to optimize surface topography by stiffness.The change of roughness orientation is irregular with the change of speed and pressure for different configurations.