NUMERICAL-EXPERIMENTAL COMPARISON OF THE PERFORMANCE OF A MIXED-FLOW FAN DESIGNED FOR ELECTRIC VEHICLES

Due to the ecological-green transition, Battery Electric Vehicles (BEV) will replace the Internal Combustion Engine (ICE) ones, since they are less pollutant in terms of carbon and noise emissions. Inside a BEV one of the major sources of noise, especially during battery charging, is related to the cooling system, which is composed of one or two axial fans and the heat exchangers. This work aims to investigate the possibility of reducing the noise emission, and increasing the efficiency of the cooling system, using a mixed-flow fan rather than an axial-flow one. In fact, it can supply comparable performances when compared to an axial fan but with quite lower rotational speed, i.e. with lower noise and reduced friction losses. In the first phase of the present work, the mixed-flow fan has been designed with a design procedure based on the available literature, starting from the inputs received from the customer, i.e. geometrical constraints, pressure rise, and power consumption. After this preliminary design process, detailed CFD simulations have been performed in order to validate the assumptions made. Thereafter the initial fan geometry has been modified to take into account the manufacturability constraints, related to the plastic injection molding process, and the fan geometry has been optimized and finalized. Different numerical approaches have been investigated to evaluate the influence of the numerical setup on the results. Finally, the optimized geometry has been prototyped and tested in a standard airflow test bench in order to assess the real performance of the mixed-flow fan and to identify the most suitable numerical approach that should be used to simulate this kind of turbomachine.