Study On Performance Of Helium Bellows Mechanical Seal Under High-speed And Dry Friction Condition

High-speed dry friction mechanical seals are used in harsh working conditions,but their design has always been a difficult point in the design of mechanical seals.In this paper,the high-speed dry friction mechanical seal is deeply studied from the influencing factors of the performance of the sealed end face,combined with the fractal theory system,to obtain the theoretical basis for designing,manufacturing,and maintaining high-speed dry friction mechanical seals.A numerical analysis model of the bellows assembly was established to analyze the changes in the equilibrium diameter and stiffness of the bellows before and after contact with the diaphragm,and the accurate closing force of the dry friction mechanical seal was obtained.The results of the study showed that when the diaphragm comes into contact,its effective diameter shifts toward the inner diameter side,and the amount of displacement is affected by the number of diaphragms and the position of the contact point.Considering the effects of film back pressure,end face deformation,end face temperature and compensation ring closing force on the performance of the seal face,a numerical analysis model of the seal face was established.Performance parameters such as pbV value,frictional power dissipation,end face temperature,wear rate,and leak rate have been obtained,which influencing dry friction mechanical seal performance.Based on the fractal theory,the bearing characteristics of the seal face were analyzed,and the load bearing characteristic parameters of the sealed end face were calculated in order,such as elastic contact area,plastic contact area,elastic contact load and plastic contact load.The analysis results show that when the sealing end face comes in contact,the micro-convex body mainly undergoes elastic deformation,and the plastic deformation accounts for a very small proportion.The real contact area only accounts for about half of the nominal contact area.A comprehensive analysis of the effects of operating parameters,structural parameters,and material parameters on the performance of the seal face was performed.The analysis results show that the structural parameters of the dry friction mechanical seal under design condition are end face height of 1.7?1.9mm,end face width of 1.4?1.6mm,load factor of 0.5-0.7,and the most suitable material parameter is the linear expansion coefficient of 6.5 × 10-6?7×10-·6/K,friction coefficient 0.7?1.3.A high-speed dry friction mechanical seal test stand was developed and set up.The frictional power consumption,face temperature,wear rate,and leakage rate of the seal face were experimentally measured.The experimental results are compared with the numerical analysis results,which shows that the theoretical analysis of the seal face performance is reliable.In this paper,the numerical analysis and experimental research on the mechanical seal of high-speed dry bellows helium gas are carried out in combination with the fractal theory.The application of fractal theory in the field of mechanical seal is expanded,which provides a new idea and method for the design and development of high-speed dry friction mechanical seal.