Design And Performance Research Of Magnetorheological Fluid Retarder For Wheelside Drive Vehicle

Retarder is an auxiliary braking device independent of the travel braking system,which can make the downhill vehicle maintain a uniform speed or smooth deceleration,and ensure the safety of drive when braking continuously.Wheel-side drive uses distributed drive form,compact installation space,the traditional retarder is large,not suitable for wheel-side drive vehicles.The magneto-rheological liquid retarder is small in size,small in weight and controllable in braking torque.Based on the advantages of magneto-rheological retarder,the paper designs a magneto-rheological retarder for wheel-side drive vehicles,and optimizes the performance of the designed magneto-rheological retarder through theoretical analysis and finite element simulation.The main research of the thesis are as follows:(1)The rheological properties,density and settling stability experiments of MRF-350 magnetorheological fluid were carried out by using Anton Paar rheometer to analyze the shear stress and viscosity of magnetorheological fluid with shear rate under zero magnetic field,the shear stress with shear rate under different current strengths and the shear yield stress with magnetic induction strength,and to establish the mathematical model of the relationship between shear yield stress and magnetic induction strength.(2)Taking a freight wheel-side drive vehicle as the research object,according to the national standard GB12676-IIA-2014 on the braking requirements of commercial vehicle retarder,combined with the selected model full load mass,wheelbase,center of gravity height and other parameters index,analyze the target braking torque required for the retarder,according to which the preliminary design of magnetorheological fluid retarder structure.(3)Maxwell software is used to conduct electromagnetic field finite element simulation of the designed magnetorheological retarder,analyze the distribution of magnetic lines of force in the magnetorheological retarder and the magnetic induction intensity at the magnetorheological fluid working gap,and optimize the inner shell thickness,the outermost magnetorheological fluid working gap and the position of the heat dissipation channel based on the magnetic induction intensity simulation results.After optimization,the magnetic lines are evenly distributed in the magnetorheological fluid retarder,and the magnetic induction at the working gap increases from 0.27 T to0.54 T when 1A current is input to the excitation coil,which exceeds the target magnetic induction of 0.5T and meets the demand of retarded braking torque.(4)Fluent software was used to simulate the flow pattern of the coolant in the cooling channel of the magnetorheological fluid retarder,and the inlet position of the coolant was optimized according to the simulation results of the velocity vector and trace diagram of the coolant in the cooling channel.The transient temperature field simulation,steady-state temperature field simulation and thermosolid coupling simulation of temperature field and structural field were carried out by Workbench software for the magnetorheological fluid retarder under braking conditions.Combined with the national standard for the retarder continuous braking 720 s requirements,the transient temperature field simulation of the maximum temperature of the retarder is 92.31℃;steady-state temperature field simulation of the retarder to reach steady state after the maximum operating temperature of 114.2℃,in the magnetorheological fluid-40℃～150℃ working temperature range;using the coupled field simulation of the maximum temperature of the magnetorheological fluid retarder thermal stress and thermal strain distribution.The results show that the designed magnetorheological fluid retarder meets the requirements of braking regulations.