Modification Of 14-Equation Model For Fluid-Structure Interaction And Vibration Characteristic Analysis Of Hydraulic Pipeline

With the development of hydraulic system towards high speed,high pressure and high power-weight ratio,the fluid-structure interaction(FSI)effect of hydraulic pipeline is enhanced and the vibration and noise are intensified,which directly affect the safety and reliability of the whole hydraulic system,the research on FSI vibration of pipeline has also become a frontier and hot issue in related fields at home and abroad.Based on the mechanism of FSI of pipeline,establishment,modification,solution and verification of14-equation FSI model for hydraulic pipeline,FSI vibration analysis and verification of pipeline with complex boundary conditions are carried out in this thesis,which has both academic research value and engineering application prospect.The main research works are as follows:(1)Establishment and modification of 14-equation FSI model for hydraulic pipeline.Based on the fluid wave equation and Timoshenko beam model,the 14-equation FSI model of straight pipe and elbow pipe unit is built and modified.In this model,the effects of quasi-steady friction term,unsteady Zielke friction term and Brunone friction term on axial vibration are considered,the impacts of gravity,centrifugal force,Coriolis force and moment of inertia on lateral vibration are taken into account.Then,the matrix expression of 14-equation FSI model is given,which lays a foundation for the subsequent resolving process.(2)Solution and test of 14-equation FSI model for hydraulic pipeline.Based on transfer matrix method(TMM),the frequency domain solution method and time domain solution method are derived: Laplace transform transfer matrix method and discrete time transfer matrix method.The mathematical models of boundary conditions and pipeline excitation for solving 14-equation FSI model by transfer matrix method are established.Taking a typical elbow pipe of C919 aircraft left wing for research object,a validation example of the elbow pipe excited by force impact is designed to study its vibration characteristics,the unity of numerical results and test results demonstrated the correctness of the model and solution method.(3)Analysis of FSI vibration characteristics of pipeline considering complex boundary conditions.Taking an aircraft hydraulic expansion ring as the research object,FSI vibration analysis system for hydraulic pipeline with complex boundary conditions is designed,and four analysis conditions are determined.The characterization method of flow pulsation and pressure boundary condition is obtained based on the flow pulsation characteristics of hydraulic piston pump.Six-degree of freedom equivalent stiffness of P-type elastic clamp is obtained by using finite element method.The vibration response of hydraulic expansion ring under different working conditions is analyzed,and the influence of system parameters on the vibration characteristics of pipeline is summarized.(4)Experimental study of FSI vibration characteristics of pipeline considering complex boundary conditions.The performance test platform of vibration property of the hydraulic pipeline is built,the test project is designed,and the numerical results of FSI vibration of aircraft hydraulic expansion ring are verified under four working conditions.The error is analyzed and the error sources is summarized in the experiment,the unity of numerical and test results demonstrated the correctness of the model and solution method.