Coupling Analysis And Optimization Design Of Multiple Physical Fields In High Circumferential Velocity Graphite Seals

With the continuous pursuit of high parameters of aero-engine,the sealing environment of bearing cavity is becoming more and more severe.As a contact sealing structure,graphite seal has excellent sealing performance and is widely used in aero-engines.In this paper,based on the four-lobe graphite seal,a multi-physical field coupling analysis model is established,the sealing characteristics of high circumferential velocity graphite seal are obtained,the friction heat transfer mechanism of graphite seal is analyzed and the structure of graphite seal is optimized.First of all,the multi-physical field coupling analysis model is established,the calculation method of seal clearance is put forward according to the experimental data,and the fluid field,temperature field and structural field characteristics of high circumferential velocity graphite seal under multi-physical field coupling are obtained.The results show that the leakage decreases with the increase of sealing circumferential velocity and increases with the increase of seal pressure difference,and the sealing gas pressure is unbalanced at the lap of circumferential groove and seal ring,the velocity distribution is uneven and is disordered near the outlet of the flow field;the maximum temperature of the sealing ring is at the lap of the ring and decreases gradually along the radial direction,and the circumferential and axial grooves can effectively reduce the temperature.The maximum deformation of the sealing ring is at the lap of the ring section,and the maximum stress is near the anti-rotation pin,in which the friction heat has a significant effect on the sealing structure.Secondly,the friction characteristics of high circumferential velocity graphite seal are analyzed by finite element method.The results show that the contact state between the sealing ring and the runway gradually develops into a close state after the initial slip and proximity,and adhesive wear occurs at the ring joint,and the sealing friction heat transfer shows that the temperature of the sealing ring is always higher than that of the runway.the highest temperature is in the lap position of the ring,and the uneven temperature distribution of the sealing ring is caused by the friction heat of the contact surface of the sealing ring and the heat conduction inside the ring.The higher the temperature and pressure of the sealing gas,the higher the maximum temperature of the sealing ring,and the high temperature is concentrated on the lap and high pressure side of the sealing ring;the temperature,deformation and stress of the sealing ring increase with the increase of the circumferential velocity;with the increase of the circumferential velocity,the maximum deformation of the sealing ring is transferred from the inner circular joint to the concave-convex lap,and the maximum stress is transferred from the inner circular joint to the anti-turning pin.The circumferential and axial spring forces have little influence on the sealing structure.When the seal ring is close to the seal seat,the smaller the axial spring force is,the better,and the circumferential spring force is better between 2N and 3N.Thirdly,the wear amount of the sealing ring is studied by establishing the Archard wear equation.The results show that the wear of the convex joint of the sealing ring is the largest,and there is a small amount of wear in the middle part of the ring and decreases to both sides,and the wear of the sealing ring is closely related to the force acting on the contact surface.According to the optimization of the joint of the sealing ring,it is concluded that the deformation and equivalent stress distribution of the sealing ring are more uniform,the wear is the smallest and the sealing performance is the best when the gap of the sealing ring is about 1 °.The maximum deformation of the triangular joint is the smallest,and the overall deformation distribution of the sealing ring is more uniform,and the comprehensive performance is better.When the lapping angle of the concave-convex joint is about 30 °,the equivalent stress distribution of the sealing ring is more uniform,the wear is the smallest,and the sealing structure performance is the best.When there is an inclination of 1 °at the end face of the sealing ring joint,the maximum deformation and wear of the sealing ring can be reduced,but the stress value will increase,and the inclination of the convex joint has no obvious effect on the sealing structure.Finally,in order to reduce the friction and wear of the sealing contact surface,the anti-fishbone groove is designed for the inner surface of the sealing ring,and the fishbone groove is optimized for the runway.The results show that the overall temperature distribution of the contact surface of the sealing ring is more uniform,and the highest temperature is concentrated in the lap joint.The deformation of the sealing ring decreases from the lap of the ring to the middle of the ring,and the stress distribution on the inner surface of the sealing ring is more uniform,but it will also increase a small amount of wear.In addition,a fishbone groove is set up in the contact area of the runway.The research shows that the runway slotting can reduce the temperature,deformation and wear of the sealing ring,but increase the stress value of the contact surface.In this paper,the sealing characteristics,leakage characteristics,friction and wear characteristics of high circumferential velocity graphite seal are obtained,and the seal structure is optimized,which provides a theoretical basis for the sealing performance and optimization of graphite seal.