Numerical simulation of novel cooling fan concept for BEVs. Investigation of aerodynamic performance of novel cooling fan concept and comparison with conventional fan concept using Computational Fluid Dynamics

Abstract

The automotive industry is heading towards fully electric vehicles, Volvo Cars, it self, is aiming at becoming a fully electric car maker by 2030. With this change comes new challenges, and one of them is the development of the cooling fan. With battery electric vehicles, focus is put on efficiency, lower noise levels and fitting the operating range of the cooling fan to meet the cooling demand of battery packs. To meet these new requirements, a new cooling fan concept never used in passenger cars before is being investigated in order to replace the conventional axial fans still employed in the automotive industry nowadays. In this thesis work, the purpose is to develop a CFD model of this novel fan concept in order to test the aerodynamic performance of the fan. The CFD simulations are performed in two different testing configurations, and the results obtained are then validated by comparing with data from testing conducted at Volvo and by the fan supplier. The same configurations are then simulated for the conventional axial fan in order to compare the performance of the two fan concepts. Finally, ram air simulations are done in order to understand the performance of the fan at different vehicle speeds. The simulations are performed using a steady state solver together with the real izable k-ε turbulence model, and the fan is modelled with the Moving Reference Frame approach. The impact of using unsteady solver with fan modelled by Rigid Body Motion as well as the impact of using SST k-ω turbulence model are also investigated. The results show a maximum deviation of less than 13% from the test data from supplier, which indicates that the model performs well. Regarding the comparison with axial fan, the results in open configuration show globally better performance and efficiency for the axial fan. However, the ducted configuration shows globally similar performance but better performance for the mixed flow fan at the points where the two fans will operate given a system of two radiators. The main conclusion from this work is that mixed flow fan does not show really better performance with a system composed of two radiators, yet the vehicle is com posed of more components that create pressure resistance and, in that case, the mixed flow fan presents some advantages in comparison to axial fan.