Study On Vibration Transfer Characteristics Of Hydraulic Pipeline System In Aircraft Engine Pylon

With the improvement of the pressure of the civil aircraft hydraulic system,the vibration of the hydraulic pipeline is becoming more and more prominent.As an i mportant part of civil aircraft,engine pylon plays a key role in transmitting the thrust and absorbing the vibration of the engine.The space configuration and working env ironment of the hydraulic pipeline in the pylon are more complex,and the load chara cteristic is changeable.Strong mechanical vibration,noise and high temperature environment can easily cause pipeline failure and even aircraft accidents.Therefore,the vibration suppression and transfer characteristics analysis of the hydraulic pipeline system in the pylon has gradually become the important content and direction of the reliability research for the aircraft hydraulic system.Under the environment of strong mechanical vibration,the vibration transfer characteristics of aircraft hydraulic pipeline system is researched,which is the premise and foundation for effective control of vibration.A certain section of the space pip eline system in the ARJ21-700 aircraft pylon is taken as the research object,and the vibration transmissibility is studied.The main research contents are as follows.(1)Considering the structure and load characteristics of aircraft pylon hydraulic pipeline system,the general mechanical vibration system consisting of airframe stru cture,support components and hydraulic pipelines is constructed.The vibration of airframe structure caused by engine is regarded as a single excitation source.The support components and hydraulic pipelines are used as vibration isolation components and vibration receptors respectively.The mobility method and four-pole parameters analysis method are used to describe and deduce the vibration transfer equation of the system,and preliminary analysis of multidimensional vibration transfer is carried out.The above research will lay the foundation for the theory and method of the follow-up work.(2)For the above mechanical vibration system,the dynamic stiffness and acceleration admittance of pipeline support components are analyzed.The airframe struc-ture is considered as an elastomer,and the quality,damping and rigidity of the support components are taken into account.Based on the classical vibration isolation theory,the two degrees of freedom physical model of pipeline support components is esta blished.In the model,the vibration of the airframe structure is the excitation source,and the hydraulic pipeline is the vibration receptor.The displacement and force tran smissibility of the support component is deduced by using the four-pole parameters analysis method,and the influencing factors of displacement transmissibility are an alyzed.(3)Mechanical analysis of tube-shell structure is carried out.Based on the theory of finite element power flow,the multidimensional vibration energy transfer of a pip eline system in the ARJ21-700 aircraft pylon area is analyzed by ABAQUS software.Identify the main path of vibration energy passing along the airframe structure and support components(bracket)to pipeline damaged parts.At the same time,the natural characteristics of the pipeline system are analyzed.(4)Modal hammering test and mechanical vibration response test for the hydraulic pipeline system in the pylon area are carried out,and acceleration response is measured.Combined vibration theory,the natural frequency and power flow transfer characteristics are experimentally studied to verify the correctness of the t heoretical analysis.