Effect Of Surface Roughness On Cavitation Characteristics Of Fluid Film And Performance Of Spiral Groove Face Seal

Because the roughness of the seal face is close to the size of the seal clearance in scale,the effect of roughness on the flow characteristics and sealing performance of the liquid film in the clearance can not be ignored.For the study of the surface roughness on the hydrodynamic mechanical seal,there are plenty of problems,such as the difficulty in simulating the surface roughness of the end face,especially for the simulation of the lubrication fluid flow in the end clearance of the micro-modeling,and the simulation of its rough boundary is still in the exploration.Therefore,this paper takes the hydrodynamic mechanical seal with liquid lubrication film as the research object,carries out the research on the influence mechanism of seal end face roughness on liquid film cavitation characteristics and sealing properties,in order to provide theoretical reference for the further research and development of high performance seals.The main research work and conclusions are as follows:Firstly,taking the upstream pumped mechanical seal as an example,an approximate characterization method of seal end surface roughness is proposed.The calculation model of the internal flow field of the lubrication film is established,which involves the surface roughness and the cavitation of the liquid film,and the effectiveness of the calculation model is verified.Secondly,the influence law of surface roughness on the cavitation characteristics and hydrodynamic effect of upstream pumped mechanical seals was studied.The results show that the micro-scale step effect formed by the rough element of the seal end face can produce the micro-cavitation and hydrodynamic effect,and make the roughness area form a tiny alternating pressure distribution of high and low pressure.When the groove area of the moving ring is rough,the pressure value of the low-pressure area in the groove is improved to some extent.The hydrodynamic effect of rough element increases with the increase of rotational speed and the roughness of the groove area.To some extent,the roughness of the groove area can inhibit the cavitation of the liquid film.The roughness on the non-groove area of the moving ring makes the pressure value of the high pressure area of outer groove root improve and expand to the groove area,weir area and dam area obviously.The higher the rotational speed,the more obvious the shrinkage and weakening of the cavitation area will be,while the liquid film micro-cavitation will not be obvious in the higher pressure area.The surface roughness of the static ring makes the high pressure area of the liquid film expand to the groove area and the dam area,and the pressure value increases with the increase of the roughness.The influence of the surface roughness of the static ring on the macro-cavitation of the liquid film is weaker than that of the other areas.Thirdly,the effects of rotational speed,medium pressure and surface roughness on the sealing performance were studied.The results show that the open force of the liquid film increases with the increase of the roughness of the groove area of the moving ring and the higher the rotational speed,the more obvious the increase is.When the non-groove area of the moving ring is rough,the lift of the open force is much larger than that of groove area,and it increases significantly with the increase of the rotational speed.The open force of the liquid film increases with the increase of the surface roughness of the static ring,and the higher the rotational speed is,the more obvious the increasing trend is.The variation of seal leakage with the roughness of groove area is relatively small.When the non-groove area of the moving ring is rough,the seal leakage is positive,but it changes weakly with the surface roughness.When the end face of the stationary ring is rough,the positive leakage at low speed and the negative leakage at high speed both decrease with the increase of roughness.The effect of roughness on friction torque is only obvious at high rotational speed.The change of the medium pressure has little effect on the variation of open force,leakage and friction torque with roughness.Fourthly,the influence of groove parameters on the sealing performance when the end face of the moving ring is rough is studied.The results show that the roughness of the end face of the moving ring has no effect on the change of the sealing performance with groove parameters.It can only increase the open force of the liquid film and shift the sealing leakage to positive leakage,and the corresponding optimal groove parameters may change.Fifthly,based on the uniform test and the Design Expert data analysis software,the predictive regression equations of sealing performance under the two models of smooth sealing end face and rough moving ring end face are established respectively.The interaction influence between groove parameters and sealing performance of the two models are analyzed by the response surface method.According to the research results,under the conditions of parameter range and the roughness of the groove area studied in this paper,when?=0.40,?=0.50,h_c=9~12?m,?=12°~14°,a greater open force can be obtained.When?=0.40,?=0.56~0.75,h_c=9~11.5?m,?=12°~16°,a fewer l sealing leakage can be obtained.