Performance Analysis And Multi-objective Optimization Of Circumferential Seal Based On Thermal-Fluid-Solid Coupling

With the overall promotion of the two major projects,breaking through the key technology of "two machines" has become the focus of the development of high-end equipment manufacturing industry.As an important part of aero-engine,the sealing performance of circumferential seal plays an important role in improving the performance of aero-engine.Aiming at the circumferential seal of the main bearing cavity of an aero-engine,this paper carries out the basic theoretical research on the thermal-fluid-solid coupling of the circumferential seal,and analyzes the sealing performance of the circumferential seal based on the thermal-fluid-solid coupling under the ideal conditions and the conditions of angular yaw and radial runout respectively.The multi-objective optimization design of the structural parameters of the circumferential seal ring is carried out by designing an experimental scheme.The main contents of this paper include:(1)The basic governing equations of gas flow field in circumferential seal are established,and the analysis and calculation of contact load,friction heat generation,follow-up characteristics of seal ring,seal condition and leakage under ideal working conditions are given.At the same time,for the circumferential seal with angular yaw,the calculation of gas load and total contact load is modified,and the calculation formula of impact load under radial runout condition is established.(2)The thermal fluid-solid coupling analysis model of circumferential seal is established,and the flow field analysis,thermal analysis,structural analysis and coupling analysis of different physical fields are carried out.The pressure distribution and velocity distribution of sealed gas,the distribution of temperature field of seal ring,the stress and deformation distribution of structural field,and the characteristic distribution law of coupling physical field are obtained.The results show that the pressure of the sealed gas decreases along the-Z axis and fluctuates greatly in the position of the lap joint,which is the main reason for the unbalanced load.After the sealed gas enters from the air guide slot and impinges to the main seal convex platform,the vortex flow is carried out in the unloading tank.The maximum temperature of the sealing ring is located in each section.The position of the main dense cover bump joint of the seal ring.The deformation and equivalent stress distribution of the sealing ring under different coupling analysis are compared.the results show that the deformation and equivalent stress distribution of the sealing ring are basically consistent with the thermal structure coupling analysis,and the maximum deformation is decreased,but the maximum stress is significantly increased.(3)The influence of runway speed,pressure difference and temperature difference on the performance of circumferential seal was studied.The results show that the maximum equivalent stress and deformation increase with the increase of runway speed,seal pressure difference and temperature difference,the change of temperature difference plays a major role in the deformation,and the change of seal pressure difference has a more significant effect on the maximum equivalent stress.The leakage of circumferential seal decreases with the increase of runway speed,and increases with the increase of seal pressure difference,which plays a decisive role in the leakage of circumferential seal.(4)The performance of circumferential seals with angular yaw and radial runout is studied.The results show that the angular deflection has an obvious influence on the pressure distribution of the sealed gas flow field.From the inlet 1 to the sealing gap,the pressure drop at the overlapping joints of the circumferential cross sections at different locations is shifted at a certain angle,and the circumferential pressure distribution at the inlet of the sealing gap presents a sinusoidal shape with a phase angle.On the contrary,the radial runout has little effect on the flow field of sealed gas.The maximum temperature of the seal ring is transferred from the convex lap joint of each section of the seal ring to the convex lap joint of the seal ring in the radial run-out direction,and the temperature rise of the seal ring is 30.5%higher than that of the ambient temperature of the sealed gas chamber than that of the ideal working condition.The deformation and equivalent stress of the seal ring increase with the increase of yaw angle and radial jump,and the radial jump is more significant.When the radial jump reaches 0.9 mm,the equivalent stress of the seal ring reaches the flexural strength and loses the sealing effect.(5)The optimal design variables of the seal ring structure parameters are determined.Based on the design and analysis of the optimal experimental scheme,the quadratic polynomial is used to fit the optimal target response surface,and the multi-objective genetic algorithm is used to optimize the sample points,and the non-dominated solution is obtained.The simulation results show that the temperature rise of the seal ring is reduced by 12%,the deformation of the optimized seal ring is reduced by 2%,the leakage of the seal mass is increased by 5%.(6)The thermal-fluid-structure coupling design and analysis system of circumferential seal is developed by using MFC,and the secondary development items in UG,FLUENT and Mechanical are used.The design and analysis of circumferential seal can be performed automatically by inputting the structural design and analysis parameters into the system interface,which greatly improves the efficiency of the design and analysis of circumferential seal.The research results of this paper provide a good basis for improving the performance of aeroengine circumferential seal and optimizing the design of aeroengine circumferential seal.