| In recent years,China’s high-speed railway technology has developed rapidly and has become a new national business card.By the end of 2022,the mileage of China’s high-speed rail will have reached 42,000 kilometers.As one of the nine key technologies of high-speed trains,the advancement and reliability of braking system technology restrict the further development of high-speed railway technology.When the train speed exceeds 400 km/h,the existing regenerative braking and disc braking systems will face more severe challenges.This thesis innovatively proposes an eddy current-magnetic track composite braking technology scheme applied to high-speed trains to solve the problem that the existing braking system is limited by the wheel-rail adhesion characteristics and the braking safety decreases at ultra-high speed.The thesis uses the research method of combining theoretical analysis,finite element numerical calculation and experimental verification to carry out in-depth research on the structural principle and braking mechanism of composite brake,electromagnetic field model,multi-objective optimization method,brake dynamics model,temperature rise and wear.The specific research contents are as follows:The preliminary design of the eddy current-magnetic track composite brake was carried out on the basis of investigating the size limit standard of railway vehicle brakes and the existing non-adhesive braking technology.The realization method and braking mechanism of eddy current braking mode and magnetic track braking mode are analyzed and studied.The permanent magnet and magnetic circuit materials are designed and selected,and the dimensions of the main components are determined.The finite element simulation method is used to simulate and verify the initial structural model.In order to deeply reveal the braking mechanism of the composite brake,the electromagnetic characteristics of the brake are modeled.The equivalent magnetic circuit method(MEC)is applied to the analysis and modeling of the static magnetic field of the composite brake,and the influence of the magnetic flux leakage between components and the overall magnetic saturation effect are fully considered.A concise analytical calculation method for transient air gap magnetic field distribution and braking force prediction is proposed.Based on the Ampere circuital theorem,the eddy current reaction magnetic field intensity distribution function is deduced and defined,and a novel double iterative algorithm is designed and programmed to realize the calculation of the transient air gap flux density.The validity and usability of the model are verified by finite element simulation.Multi-objective optimization of the main structural parameters of the composite brake is carried out.A multi-objective optimization model is established for the permanent magnet brake section and the electromagnetic brake section,with the maximum magnetic attraction,the minimum permanent magnet consumption and the minimum excitation power as the optimization objectives.The Kriging surrogate models of the two brake sections are obtained through training,and the Pareto optimal frontier solution set of the optimization objective is obtained by using the improved fast non-dominated sorting genetic algorithm(NSGA-II).After optimization,brake performance is further improved.The braking performance of high-speed trains combined with composite brakes is studied,and a braking dynamics model is established by taking CRH380B high-speed trains as an example.Using theoretical analysis and Matlab/Simulink simulation tools,the braking deceleration process of high-speed trains after the fusion of composite brakes is studied,and the characteristics of braking distance,braking deceleration,and braking speed are simulated and calculated.A numerical model of the temperature field of the wear plate is established on the basis of the basic theory of heat transfer.The time-varying equivalent heat source model of the wear plate and the calculation method of the time-varying convective heat dissipation coefficient are studied.Using the Fluent finite element simulation software,the numerical simulation is carried out on the temperature field distribution inside the wear plate and the brake section during the magnetic track braking process.According to the Archard wear theory,the wear plate wear model under the magnetic track braking mode is established,and the dynamic wear process of the wear plate during the magnetic track braking process is studied.Finally,the prototypes of the permanent magnet brake section and the electromagnetic brake section were designed and manufactured with optimized structural parameters.Design and build a test bench that can simultaneously realize the measurement of suction force and eddy current braking force.The maximum magnetic attraction force in the static state and the eddy current braking force in the dynamic state are tested.The test results show that the error between the maximum magnetic attraction force and the theoretical simulation calculation is 1.2%and that a braking deceleration of not less than 0.3 m/s~2 can be achieved in the magnetic track working mode.In the eddy current braking mode,the braking force is not less than 1.2 k N,which has certain advantages compared with the Japanese"Shinkansen"rotating eddy current braking device. |
