Development of Pressure Distribution Model in Ventilation Ducts of the Brake Disc with Forced Cooling
As the brake disc rotates, air flows into the ventilation ducts. The air flow cools the non-working surfaces of the brake disc during forced cooling. To increase the intensity of heat transfer from heated surfaces, forced cooling systems are often used. The main task of the systems for forced cooling of friction units is to reduce the thermal load. The heat transfer from the heated surfaces of the brake disc depends on the number of changes in the cooling air, i.e. from the throughput of the ventilation device. The parameters that affect the throughput of the ventilation device can be both geometric and aerodynamic (inlet pressure, coordinates of the cooled air supply source and its angle of attack). The paper presents theoretical studies in the form of a model of pressure distribution inside the ventilation ducts. According to the developed model, a pressure inversion is observed inside the ventilation ducts during the rotation of the brake disc. This affects the filling of the brake disc ventilation ducts with air, and subsequently, the thermal loading of the entire friction unit. The rib of the ventilation ducts in the developed pressure distribution model is represented as a plate placed in the air flow at a certain angle of attack. Using the calculation method, the conclusion about the pressure drop along the entire length of the rib of the partition of the ventilation duct was justified. The resulting pressure distribution inside the ventilation device can be replaced by the resulting force. Depending on the direction of action, it can be either an auxiliary force during braking or a resistance force. The direction of action of the resulting force depends on the sector of installation of the source of forced supply of cooling air. To confirm the theoretical research on the location of the cooled air supply source, computer simulation was carried out in the ANSYS Fluent software module. In the framework of computer modeling, the influence of the location of the air flow source on the distribution of pressure inside the ventilation ducts of the brake disc was investigated. The results obtained make it possible to speak about the influence of the location of the cooling air source on the pressure distribution inside the brake disc ventilation apparatus. This confirms the hypothesis that the coordinates of the air source and the angle of attack can be parameters for optimization when creating forced cooling systems. In addition to this result, computer simulation in the ANSYS Fluent module based on the CFD model made it possible to propose the points of application of the resulting forces relative to the length of the ventilation duct, depending on the coordinates of the location of the forced air supply source. The theoretical calculations are confirmed both by the calculation method with the substitution of the initial data in the distribution model, and by the method of computer modeling of the ventilated brake disc. The research results can assess the effectiveness of optimization of forced cooling systems, from the point of view of installing an air supply and pressure distribution in the radial ventilation ducts of the brake disc.