Performance Analysis And Multi-Objective Optimization Of Circumferential Seal For Oil Cooling

Circumferential seal is an advanced seal technology that has been successfully applied to the sealsystem of aero-engines to improve the effects of oil leakage from the bearing cavity,and improve the life of the engine and the utilization rate of the oil.Considering the influence of oil on the performance of the circumferential seal,the theoretical model of circumferential seal oil cooling is established to analyze the friction and wear of the main sealing through experiments,which lays the foundation for the analysis of friction heat and structural field.Analyzing the law of flow field,temperature field,structure field and coupled physical field,and calculating the leakage amount of seal gas.At the same time,carry out multi-objective optimization analysis,and complete the secondary development of the circumferential seal oil cooling software.(1)Establish mathematical model of circumferential seal oil cooling.Simplify the cooling process of circumferential seal oil cooling,and summarize the models of circumferential seal heat generation,heat conduction and heat dissipation.An approximate replacement model for the convective heat transfer coefficient of the sealed runway,gas cavity and bearing cavity is established.At the same time,complete the circumferential seal friction heat generation and heat distribution model,and obtain the internal wall surface of the seal runway and the internal wall surface of the oil force analysis model.(2)The friction and wear rules between graphite M210 and sealing runway 40CrNiMoA is analyzed,which lays a foundation for the calculation of friction heat and structure field in temperature field.The average friction factor increases with the increase of sliding speed,and shows a trend of increasing and then decreasing with the increase of contact stress and temperature.The wear rate of graphite M210 and 40CrNiMoA materials increases with the increase of sliding speed and contact stress.The wear rate of M210 increases and then decreases with the increase of temperature.40CrNiMoA wear rate increases with the increase of temperature.The SEM analysis showed that the wear mechanism was mainly abrasive wear.(3)The analysis of circumferential seal flow field,temperature field and structural field is carried out,and the optimal oil supply and leakage of sealing gas for circumferential seal is given.The oil on the wall surface is evenly distributed.Along the direction of the inner wall to the outlet,the oil pressure has a decreasing trend and increasing afterwards,and the oil speed has a decreasing initially and increases afterwards.With different inclination angles of the inner wall,the oil speed first decreases and increases afterwards,and the oil pressure shows an increasing-decreasing-increasing change pattern.Compared with the temperature field without oil cooling,the maximum temperature of the sealing runway decreases by 177.2℃when the oil is cooled,but the maximum temperature difference of the sealing runway increases.The heat transfer coefficient of the inner wall along the oil flow direction presents decreasing-increasing-decreasing rule.The maximum value of the heat transfer coefficient of the inner wall at the position of the main sealing.As the speed and cooling oil inlet ratio increases,the maximum temperature of the sealing runway decreases instead.Under different inlet pressures,the temperature of the inner wall drops rapidly along the axial position,and then changes steadily.The heat transfer coefficient increases and decreases afterwards along the axial position,while the heat transfer coefficient of the inner wall surface oil corresponding to the main sealing area reaches the maximum.Combining the wall heat transfer coefficient and cooling state,the optimal oil supply pressure is 0.6 MPa.The results show that the maximum deformation and maximum stress of the sealing runway are near the outlet.The deformation and stress are the same among each sealing ring,the uniformity of deformation distribution on the main sealing surface is worse than that on the auxiliary sealing surface,with larger stress values on the main and auxiliary sealing surfaces.Deformation of sealing runway and each seal ring of each flap under fluid-solid coupling is not uneven.The effect of temperature field on the structural field is greater than that of the flow field.The total leakage volume of sealing gas is 1.73 ×104m3/s.(4)Completing the multi-objective optimization analysis of circumferential seal oil cooling.Research the influence of each optimization design variable on the optimization target,establish the influence degree of different optimization design variables on the optimization target through local sensitivity,and complete the accuracy of the quadratic polynomial fitted response surface.The multi-objective genetic algorithm MOGA was used to establish the Pareto space map,and it was found that the maximum temperature of the sealing runway decreased by 2.6%,the maximum stress of the sealing ring decreased by 22.2%,the maximum deformation decreased by 12.2%,and the leakage decreased by 23.1%.(5)Develop circumferential seal oil cooling analysis software to simplify finite element operation steps and improve work efficiency.Rely on Fluent scripting language,APDL and C++language to realize the data interaction of the crucial parameters,and use Journal and Insert Command commands to realize the program call.The research results provide quantitative analysis data for the performance analysis of high linear velocity graphite circumferential seals,and provide theoretical support for the optimization of the performance and life of circumferential seal devices in the future.