Research On Vibration Reduction Technology Of Aircraft Converging Hydraulic Pipelines Under Two Excitation Sources

As the “life channel” for aircraft hydraulic system to transmit energy and actuator action,pipeline vibration is a hidden danger of flight safety.The aircraft hydraulic pipeline is subjected to the high pressure pulse excitation from the pump source and the random vibration excitation transmitted by the engine through the body in the working environment.These two excitation sources may cause severe fluid-solid coupling vibration and structural vibration of the pipeline and its components.If the natural frequency of the pipeline system is close to the pulsation frequency of the pump and the fundamental frequency of the engine,it is very likely to induce mechanical resonance.In addition,the high-pressure pulsating oil output by the dual-pump cooperative work is converged through the three-way joint to meet the peak hydraulic requirements of flight control during take-off and landing,which is common in large aircrafts.In the complex vibration source environment with both double excitation sources and double pump confluence disturbance,how to integrate the confluence pulsation control and the structural layout optimization of pipeline support parts to realize the vibration suppression of the confluence pipeline structure has important theoretical research significance and engineering application value.Therefore,this thesis mainly launches the following research work:Vibration simulation analysis and experimental verification of aircraft hydraulic pipeline.The corresponding simplified modeling method is proposed for the CAD model of aircraft hydraulic pipeline,and the contact setting and mesh type suitable for aircraft hydraulic pipeline are selected.The correctness and effectiveness of the simplified model and simulation analysis method are verified by comparing the natural frequency and vibration mode between the modal test and the simulation simplified model.Analysis and equivalent simplification of pulsating excitation of the pump source.Combined with the test results under pulsating excitation,on the one hand,the rationality of the dynamic simulation method is verified.On the other hand,the mechanism of pump source pulsation is analyzed analytically.Three methods,namely FFT analysis combined with harmonic expression fitting,analytical solution of pressure pulsation and Fourier series simulation,are used to obtain good fitting effect on the test pressure pulsation curve.The equivalent simplification based on single sine function is proposed according to the frequency doubling characteristics of pump source pulsating excitation,and the feasibility of using single pulsating pressure with fundamental frequency to approximate the equivalent periodic pulsating pressure with high harmonics is demonstrated.Research on the suppression technology of pressure fluctuation amplitude by the phase difference of double pump confluences.The functional expression of the relationship between the pressure fluctuation at the outlet of the pipeline and the amplitude and phase of the pressure fluctuation at the two inlets is established.The numerical solution curves of the outlet pressure fluctuation function under two typical working conditions are analyzed by MATLAB programming.The consistency with the numerical solution of the equation is verified by the finite element fluid-solid coupling simulation analysis results.For the twopump cross-phase pressure supply pipeline,the outlet pressure changes with the phase difference.The outlet pressure pulsation under the excitation of the same type of double pump increases with the phase difference of the two confluence pulsation,and the pressure pulsation amplitude gradually weakens to the mean level.The pressure pulsation amplitude is worthy of effective suppression.Vibration reduction design of combined hydraulic pipeline for dual excitation sources.The optimization mathematical model is established with the support position as the design variable,the engine fundamental frequency and the pump source fundamental frequency as constraints,and the objective is to reduce the stress response under engine excitation.The multi-objective genetic algorithm is used to obtain the dynamic optimization solution.Then,the 180° pulse response of the two-pump staggered phase is solved,and the double excitation stress response on the confluence pipe is compared under the condition of no phase difference before optimization and 180° phase difference after optimization.The numerical analysis results show that the stress value of the optimized pipeline structure is significantly reduced.The integrated vibration control technology of structural optimization design and dual pump phase stagger adjustment provides a useful reference for the vibration reduction design of the assembly pipeline.