Numerical Study of Heat Transfer and Speed Air Flow on Performance of an Auto-Ventilated Disc Brake

Abstract

In the braking system, the heat dissipation generated by the friction between the disc and pad should be evacuated as quickly as possible. In this work, five common different automotive disc brakes were studied through mathematical theories of heat transfer and numerical methods using the ANSYS software. In addition, a direct comparison between experimental, theoretical, and simulation values found in the open literature was performed to propose a disc brake with an improved geometry in terms of dissipation of heat transfer. The numerical results were considered to propose two possible solutions of disc brake geometries using N-38 ventilation blades used in aeronautic engineering. An improvement in temperature dissipation was achieved by approximately 23.8% compared to the five geometries analyzed with a simple type N-38 ventilation blade. The heat dissipation in the brakes strongly depends on the geometry of the disc, the geometry of the blades, the material from which it is manufactured, the material of the pad, the weight of the vehicle, and the operating conditions, as can be verified with mathematical calculations and experiments. The results obtained demonstrate that the discs can be used effectively in extreme working conditions (80 km/h and 33°C), without affecting the safety of the occupants and the braking system.

Mechanical and Dynamic Maps of Disc Brakes under Different Operating Conditions

“…It was observed that the vehicle braking deceleration as to the angle of descent increases, the decelerations increase because the gravitational resistance increases, considering that, in this particular case, it is also a propelling force. It is important to mention that the results of the Equations presented in Table 6 were used to develop 2D maps, considering Equations ( 13), (17), and (18) under different braking operating conditions. Currently, in many cases, the driver could not exert enough force to stop the vehicle at the ideal distance; therefore, the force is multiplied using levers or hydraulic circuits, thus obtaining a greater friction force.…”

“…Depending on the force applied to the pedal, the higher efficiency of the process is obtained. On the other hand, the conditions of mathematical calculations are considered suitable concerning experimental and numerical calculations [17,29]. The mathematical analysis of the brake system is associated with braking force, resistance coefficient, rolling coefficient, deceleration, pedal force, peripheral speed, dissipated energy, braking deceleration, and dissipated power that aid to obtain the thermal calculations such as rise in temperature, surface temperature, and instantaneous temperature applying Newton's cooling law.…”

“…All equations were obtained from [1, 17,30] from different bibliographic sources. The disc brake characteristics considered in this study depend on the vehicle and disc brake capacity with the geometry detailed in Figure 1.…”

“…Braking Time Mathematical calculations (mechanical, dynamic and, thermal) were developed considering the assumptions proposed by [17], and the equations used are summarized in Table 3. Notice that this calculation is consecutive of each of these, which means that in order to use Equation ( 7), it is necessary to have calculated Equation (1).…”

“…Moreover, for a higher speed, the airflow counteracts the amount of heat generated at the moment of braking, as there is more energy to reduce [16]. García-León et al [17] evaluated five different geometries of disc brake to design a new disc with improved heat transfer properties using N-38 type blades. With these blades, the temperature dissipation was around 23.8%, related to the others studied through CFD analysis using ANSYS.…”