Frequency Domain Characteristics Analysis Of Fluid Structure Coupling Vibration Of Civil Aircraft Hydraulic Bending Pipeline

As the blood vessels and muscles, hydraulic system is a sign of the aircraft physique, its domestic degree directly affects the advancement and development of our large aircraft project. It is of great significance to in-depth study of the hydraulic system. Vibration is the main factor causing the failure of hydraulic system, with the development of aircraft hydraulic system to high speed and high power weight ratio direction, how to suppress the vibration becomes particularly important. Most of the hydraulic system vibration is caused by the fluid structure interaction induced by flow pulsation of hydraulic pump flow, especially in the area of curve pipe, where the fluid structure interaction is more intense. Subject to the restrictions of the plane space, elbow is ubiquitous, its spatial structure, pipe material and fluid parameters will affect the vibration characteristics. Analysising of the effects of these parameters has important directive significance to the design of the pipeline.In view of the domestic civil aircraft flow solid coupling vibration in hydraulic elbow, this paper analysis laws of space structure, pipe material and fluid parameters affecting flow solid coupling frequency domain characteristics. The main research work is as follows:(1) 14-equation fluid structure interaction dynamics model of straight and curved pipe was established. The transfer matrix method for solving the model was researched. Boundary conditions under the mechanical shock excitation were derived, which can realize the accurate calculation of the pipeline.(2) In view of four situations- single bend, fixed length pipe bending, indefinite length pipe bending and the multi bend pipe- using the fluid structure interaction calculation method, laws of bending parameters of pipeline affectiong fluid structure interaction frequency domain characteristics were analyzed.(3) The influence of fluid pulsation frequency and fluid velocity on fluid structure interaction vibration was analyzed, and the influence of pipeline material parameters on natural frequency of the pipeline was analyzed.(4) Took expansion ring as the research object, analyzing the the luid structure interaction frequency domain characteristics, and using the conclusions of former analysis to optimize bending angle; Natural frequency of a segment pipe on the position of wing tip was analysised, and conducted normal flight environment analysis and functional impact analysis, at the same time the bending angle of the pipeline were optimizationed.(5) The modal experiment theory was introduced. The laws of bengding angle of fixed length pipe affecting natural frequency were verified through experiments. The influence of fluid pulsation frequency and velocity was verified through flow pulsation experiments; For the pipe in wing tip, modal experiment, normal flight vibration environment experiment, unctional impact experiment were conducted, which verified the accuracy of the simulation.