Optimization And Experimental Test Of Drag Torque Model For Wet Brake Based On Cavitation Effect

Brakes are an important component of vehicle braking systems,and wet brakes are widely used in heavy-duty vehicles due to their superior performance.During the non braking period of the wet brake,due to the viscous effect of the cooling oil,there will be generate drag torque,causing a portion of the engine’s power to be consumed in the brake,resulting in a decrease in the overall efficiency of the transmission system.When the drag torque is too high,the problem of high friction plate temperature and reduced service life of the friction pair may also occur.Therefore,the optimization of the model based on the theory of drag torque has always been a focus of relevant research.In order to improve the accuracy of the theoretical model of drag torque,a detailed analysis is conducted on the cavitation effect in the oil film flow field at medium and low speeds.The cavitation effect can cause air to enter the flow field in advance,damage the integrity of the oil film,and cause prediction errors.In this paper,the cavitation effect in the oil film flow field is modeled by using the cavitation inception theory,calculated by using the finite difference method,and analyzed the calculation results to study the influence of groove parameters and working parameters on the cavitation effect.Afterwards,based on the differential equation of fluid motion,the flow field of the wet brake was modeled,and combined with cavitation theory,an optimized drag torque model was obtained.An in-depth analysis was conducted on the cavitation effect and drag torque in the flow field using an optimization model.According to the theoretical part,conduct a wet brake drag torque test to verify the optimization model through the test results.At the same time,analyze the influencing factors of drag torque to verify the correctness of the theoretical analysis.Finally,by comparing and calculating the torque models with different grooves,the influence of groove structure on the torque was analyzed.The research results indicate that cavitation effect does not occur in the flow field without grooves,but in the flow field with grooves,cavitation effect occurs in the upstream region of the radial groove.The larger the width of the groove,the deeper the depth of the groove,the larger the initial cavitation area,and the stronger the cavitation effect.The initial cavitation area fraction increases and then decreases with the increase of rotational speed,and cavitation effect does not occur in the high rotational speed region.The larger the flow rate,the greater the maximum value of the initial cavitation area fraction,and the corresponding rotational speed of the maximum value is also higher.The larger the gap,the smaller the maximum value of the initial cavitation area fraction,and the smaller the speed range in which cavitation effects occur.The superiority of the model was verified by comparing the theoretical model with experimental data.In terms of predicting the peak drag torque discharge,the optimized model reduced the error by 72.16% compared to the pre optimized model.Within the speed range of 0-2000 r/min,the optimized model reduced an average error of 55.71%.The optimization model has better optimization effect and smaller prediction error under medium to high traffic conditions.By calculating and analyzing the drag torque model with different grooves,it is found that the structural features of the spiral strip,such as radial composite grooves,waffle grooves,and double arc grooves,can all reduce the drag torque.Among them,the double arc groove has the best torque reduction effect,followed by the Waffle groove,and finally the spiral belt radial composite groove.In addition,the increase of grooves will also reduce the drag torque,with the radial groove having the most obvious torque reduction effect,approximately reducing the drag torque by 25.9%,followed by the closed groove and finally the spiral groove.