Research On End Face Deformation And Liquid Film Vaporization Characteristics Of High Temperature Noncontact Mechanical Face Seal

When high temperature non-contact mechanical face seal being researched,thermodynamic deformation of seal end face and vaporization of liquid film in seal gap are difficult to deal with.The collective effect of end face deformation and the liquid film vaporization will have a significant impact on the sealing performance,which will lead to the sealing failure or even worse,the destruction of seals.So,it is of great academic and practical value to carry out related research in depth.In this paper,a fluidsolid-thermal coupling model concerning end face thermal deformation and film vaporization was established to study the influence mechanism of the deformation on the vaporization characteristics and the relationship between the sealing performance and the end face deformation.The main conclusions are as follows:1.On the basis of investigation and theoretical analysis,a fluid-solid-thermal coupling model,which involves high temperature sealing medium,viscositytemperature relationship,thermal deformation of sealing ring and vapor-liquid twophase flow of lubrication film,was established and verified.2.The established model being used,the end face deformation and the vaporliquid two-phase flow field were simulated and analyzed,and the influence law of the end face axial deformation on the lubrication film was studied.Studies have shown that axial deformation of the end faces of the rotational and stationary rings is greater on the inner diameter side than that on the outer diameter side.The deformation of the inner diameter side takes wavy changes periodically along the circumferential direction,the maximum deformation is located in the weir area on the windward side of the spiral groove,while the minimum deformation in the leeward side of the spiral groove;axial deformation of the end face results in the increase of the high pressure area and the contraction of the negative pressure area;the film temperature is affected considerably by the end face axial deformation because it lets the film temperature in the sealing dam area and the high pressure area in the groove rise and the low temperature area inside the groove shrink slightly.It was also found that the degree of vaporization of lubricating film in groove-weir area is obviously higher than that in dam area.The fiercest vaporization occurs at the weir area near the leeward side of the groove and some vaporizes slightly at the inner groove root on the groove leeward side.The vaporization of the groove area shows periodic variation.Axial deformation of the end face leads to a higher vaporization degree in whole and a significant reduction of the weak vaporization area.3.Research on the influence law of working condition parameters on axial deformation of end face and vaporization characteristics of liquid film reveals that the influence of sealing medium pressure on the end face axial deformation is limited;as the medium pressure increases,the lubrication film vaporization is inhibited,and the high vaporization area compresses to the low-pressure area on the inner diameter side.With the increase of rotation speed,the end faces axial deformation is dented,and the degree of vaporization in the groove-weir area is obviously enhanced.When the temperature of the sealing medium increases,the end faces axial deformation increases obviously,and the circumferential wavy deformation near the inner diameter side also increases.The vapor volume fraction in the sealing dam area increases first and then decreases as medium temperature rises,while the vapor volume fraction in the grooveweir area apparently increases.4.Research on the influence law of working condition parameters on the internal temperature and internal equivalent stress distribution of rotational and stationary rings shows that the back and outer diameter areas of the rotational ring are high temperature areas,the temperature of the stationary ring is higher only at the outside diameter of the end face.The temperature of the outer diameter side of the sealing end face is the highest and gradually decreases to the inner diameter side;the equivalent stress inside the rotational and stationary rings is larger on the back side and smaller on the end face side.The maximum stress of both the rotational and stationary rings appears at the outer diameter of the back side.As the medium pressure increases,the temperature at the outer diameter side of the rotational ring increases,but it has little effect on the internal equivalent stress of the sealing ring,and the increase of the maximum stress of the stationary ring is much larger than that of the rotational ring.With the increase of rotational speed,the local temperature of the rotational and stationary rings decreases,and the stress in the stationary rings tends to expand from the low stress zone to the back of the ring.The maximum stress of the rotational and stationary rings decreases with the increase of rotational speed.With the increase of medium temperature,the temperature of the rotational and stationary rings increased significantly,and both showed the change law of the expansion of the high stress zone,the maximum stress value increased,and the low stress area decreased.The maximum stress value of the silicon carbide rotational ring was much higher than that of the stationary ring,and it tended to cause plastic deformation more easily.5.The circumferential and radial deformation and stress characteristics of the sealing ring are discussed and analyzed.The research shows that the increase of medium temperature has obvious influence on the radial deformation of the seal ring,but the radial deformation stress is much smaller than that of the axial deformation.The reverse torsional deformation of the cross sections of the rotational and stationary rings under high temperature conditions was studied,which resulted in the convergent seal clearance with narrow inner diameter and wide outer diameter;thermal deformation leads to the increase of leakage with the increase of medium temperature;under high temperature conditions,the stiffness of the lubricating film decreases,and the bearing capacity of the lubricating film decreases.At the same time,the influence of lubrication film stability,end face contact and leakage on the lubrication failure caused by high temperature sealing medium is preliminarily analyzed.