Research On Performance Optimization And Experimental Of Aircraft Actuator Seal Based On Step Seal

Reciprocating sealing is a type of fluid sealing technology.Its simple and compact structure is widely used in aerospace,engineering machinery,mining engineering and other fields to achieve sealing effects and prevent foreign substances from entering the mechanical system.In mechanical systems,the failure of the reciprocating sealing ring will directly affect the efficiency of the whole machine and cause economic losses,and in serious cases will cause a safety accident.Aircraft actuator seal is a reciprocating seal.It is an important part of the flight control function.Its sealing performance directly affects the smoothness and safety of aircraft.In this paper,the step seal applied to aerospace actuators was the research object of reciprocating seals.Based on the reciprocating seal mechanism and theoretical analysis of the system,a fluid-solid-heat multi-field coupled reciprocating seal hybrid lubrication numerical model was established.Based on the forward and reverse solution theory,the change law of each parameter of step seal under different working conditions was analyzed,and the influencing factors of the sealing performance of the reciprocating seal system were qualitatively and quantitatively analyzed in combination with experimental measurements.Aiming at improving the sealing performance and prolonging the service life of the seal,an optimization scheme based on the step seal and piston rod coating materials was proposed.Based on the reciprocating seal mechanism and theoretical analysis of the system,a fluid-solid-heat multi-field coupled reciprocating seal hybrid lubrication numerical model was established.In this paper,a set of multi-objective optimization methods for reciprocating sealing systems based on a combination of theoretical analysis,bench experimental testing,and interface micro-testing analysis was formed,a reciprocating sealing experimental bench was designed and built,a bench test method and performance parameter test method was constructed,which has important theoretical significance and engineering value.First,researched the material of the step seal,and tested the materials of the components of the step seal——D-ring and step ring through uniaxial compression experiments,to obtain the stress-strain relationship and elastic modulus of the material.A material constitutive model was established to provide material parameters for finite element simulation analysis.Then used ABAQUS software to carry out finite element simulation analysis of the step seal.By setting the structure,material,working conditions and other parameters of the reciprocating seal system,a finite element model of the reciprocating seal system was established.The analysis obtained the stress-strain cloud diagrams,the contact pressure distribution and contact width of the step lip and the bottom of step seal in the interference installation,different oil pressure and different reciprocating stroke conditions.It provides an effective basis for the theoretical calculation of the reciprocating seal.Secondly,based on the sealing mechanism of the reciprocating seal,the Reynolds equation was solved in the forward direction,and the oil film thickness formula and system leakage formula for calculating the instrokel and outstroke of the system were obtained,and a hydrodynamic model was established.The G-W model was used to derive the contact stress formula between the step ring lip and the piston rod,and a contact mechanical model was established.The contact pressure distribution of the stepped ring lip was obtained through the finite element simulation analysis of the step seal,and a solid mechanical model was established.According to the viscosity-temperature effect of the lubricating oil,the influence of temperature on the viscosity of the lubricating oil was obtained,and thermal analysis was performed.Based on the above four analyses,the fluid-solid-thermal coupling of the reciprocating seal system was considered,and the dynamic pressure effect of the inlet was taken into account.A multi-field coupled reciprocating seal hybrid lubrication numerical model was established.Then,based on the forward and reverse lubrication solution theory,taking the nitrile rubber D-ring and step ring as the PTFE seal with MoS₂ and glass fiber as an example,the piston rod coating material is chromium(Cr),obtained contact stress distribution,oil film thickness,leakage(reverse pumping rate),friction and other sealing performance parameters under different oil pressures(10MPa,20MPa,30MPa and 35MPa),different reciprocating speeds(100mm/s,200mm/s,300mm/s,400mm/s and 500mm/s),and different temperatures(-60?,-40?,20?,40?and 100?)by using Matlab software.The influence of different operating conditions on the sealing performance of the reciprocating seal system was analyzed according to the actual situation.Thirdly,a reciprocating sealing experimental bench was designed and built.The piston rod was fixed at one end of the experimental bench to eliminate its inertial force.The measurement and control system was used to control the hydraulic cylinder to perform reciprocating motions at different oil pressures,different reciprocating speeds and different temperatures.The friction force data of the reciprocating seal system under different working conditions was obtained through a tension and pressure sensor installed at the fixed end of the piston rod,and compared with the numerical results obtained through the numerical solution of the mixed lubrication model of the reciprocating seal.The results of the two were basically the same,which verified the correctness of the numerical model and calculation results of the reciprocating seal mixed lubrication.Then,based on the established reciprocating seal hybrid lubrication numerical model,the leakage and friction were used as the evaluation index of the sealing performance of the reciprocating seal system.The influence of different structural parameters and materials on the sealing performance of the system was obtained through numerical calculation and analysis.Therefore,the appropriate surface topography parameters,lip surface topography parameters and materials were selected to optimize the design of the sealing ring.The step rings of different step ring materials(with MoS₂and glass fiber,copper powder,and carbon fiber added PTFE)were used for reciprocating seal bench experiments.The correctness of the theoretical calculation was verified through experiments,and an optimal design scheme of the reciprocating seal was proposed.Finally,based on the established reciprocating seal hybrid lubrication numerical model,the effects of different coating materials(Cr and DLC)of the piston rod on the leakage and friction of the reciprocating seal system were obtained through numerical analysis.Piston rods with different material seals and coating materials were selected for reciprocating seal bench test experiments.The correctness of the optimization conclusions obtained by theoretical calculations was verified by experiments.At the same time,the step seals used in the experiments were tested for surface abrasion,surface morphology,and abrasion surface element measurements of the seal lips,and the reason for the seal wear was deduced.Based on theoretical calculations,reciprocating seal bench experiments and friction and wear measurement experiments,an optimization scheme for piston rod coating was proposed,and a multi-objective optimization design method for reciprocating seal systems based on friction,leakage,and friction and wear rates was proposed.