| Hydraulic retarder,as the auxiliary brake of automobile,has been widely used in the field of commercial vehicles with its unique advantages of hydraulic retarder braking.However,the hydraulic retarder working under high speed conditions will cause cavitation erosion,which will cause discontinuities in fluid transmission and exacerbate the vibration and noise of automotive transmission systems,which will seriously affect the reliability of the system.Bubble burst during the process will also impact the solid wall surface of the retarder,causing fatigue damage to the wall surface,thereby shortening the service life of the hydraulic retarder.Therefore,it is particularly important to suppress the cavitation erosion of the retarder.Aiming at the above problems,this study takes a reference model of a retarder as the research object,and studies the cavitation mechanism of the transient coupling flow field of the hydraulic retarder.Based on this,the multi-objective optimization design of the structural parameters is carried out.The main research contents of this study are as follows:1.The numerical calculation method study of the transient coupling cavitation flow of the hydraulic retarder is carried out.For the transient two-phase flow in the cavitation process of the hydraulic retarder,the current advanced Hybrid RANS/LES turbulence model is introduced to calculate the cavitation flow.The model verification is performed using the prediction error of the braking torque as a criterion,and the comparative analysis of the simulation results of different turbulence models is also studied.2.The transient cavitation flow field of the retarder based on the SBES model with high calculation accuracy in Hybrid RANS/LES is analyzed.The main analysis is the cavitation erosion mechanism of hydraulic retarder and the transient evolution law of important physical quantities in cavitation flow field.3.Based on the numerical calculation of the transient coupling cavitation flow field of the hydraulic retarder,a multi-objective optimization design of structural parameters of retarder is carried out.In the optimization process,the blade wedge angle,blade inclination angle,and the number of oil inlets and outlets of the hydraulic retarder are selected as optimization design variables.The braking torque of the hydraulic retarder,the total flow channel volume,and the total volume of bubbles generated under high-speed conditions are selected as the optimization objective.The NSGA-? is selected as optimization algorithm,specifies the weight and scale factor of sub-objective to obtain the optimal solution.Finally,the braking torque,volume,bubble volume value and optimization rate at each speed are compared and analyzed.4.The sensitivity analysis of structural parameters and multi-objective optimization process is carefully studied.On the one hand the correlation and influence of structural parameters on each optimization sub-objective is analyzed.On the other hand the multi-objective optimization process of the retarder is analyzed in detail.The purpose is to find the reason why the retarder performance is improved after optimization. |
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