Thermal Characteristics Analysis And Heat Transfer Enhancement Research Based On Heat Pipe Structure Of Ventilated Brake Disc

As one of the core components of vehicle braking system,the quality and performance of the brake are very critical.From the point of energy,most of the heat energy converted in the process of automobile braking is absorbed by the brake,which makes the surface temperature of brake rise sharply in a short time,causing the phenomenon of heat decline on the surface of brake and the decrease of braking performance.The thermal and stress coupling analysis of the brake is carried out,and then the heat transfer enhancement design is carried out,which is helpful to improve the performance of brake,and it has very important research value.This paper takes ventilated brake disc of a passenger car front wheel brake as the research object,establishes a three-dimensional model according to the actual size of the brake,and carries out the numerical simulation and related experiments of the thermal machine coupling.The results show: In emergency braking,the radial,circumferential and axial temperatures of ventilated brake disc have experienced a rapid increase and then a slow decline.The friction heat generation rate is dominant in the initial stage of braking process,while the surface convection heat transfer is gradually enhanced in the late braking stage.Besides,the radial temperature difference of ventilated brake disc is as high as 148 ?,which is obviously larger than the circumferential temperature difference.During the whole braking process,the equivalent stress is mainly expressed as thermal stress,the maximum value is about 150 MPa,which is far less than the safety strength required by the brake disc material.On the premise of ensuring the normal structure strength of the ventilated brake disc,combined with the above analysis results,the heat transfer research of high temperature zone on the surface of normal ventilated brake disc is carried out by using the heat pipe with good uniform temperature performance.It is shown that heat pipes are embedded on both sides of ventilated brake disc along the rotation direction of brake disc.Using the excellent heat conduction performance of heat pipe,the heat of high temperature area of ventilated brake disc is guided to the non friction area,and the highest temperature of ventilated brake disc is reduced,thus the braking performance of brake is improved.Two kinds of brake discs are tested under three different braking conditions: emergency braking,continuous multiple braking and long slope continuous braking.By comparing the experimental results,it is concluded that the overall temperature distribution of heat pipe ventilated brake disc is more uniform than that of normal ventilated brake disc.Under the three braking conditions,the temperature uniformity in radial direction of ventilated brake disc respectively increased 39.13%,46.67%,26.39%.Finally,the heat flux method is applied to simulate emergency braking,continuous braking and long slope continuous braking conditions of heat pipe ventilated brake disc and normal ventilated brake disc respectively.The analysis results show that the peak temperature of heat pipe ventilated brake disc decreases with the three braking conditions,and the temperature uniformity in the radial direction of ventilated brake disc increased by 13.43% and 18.62%,respectively.