Active grille shutter systems development of front engine vehicles

In this study, it is aimed to implement a methodology of analyzing the engine compartment thermal performance and the vehicle drag of an M2-class vehicle. The work comprises two phases; the preliminary phase is to obtain air and thermal flow under-the-hood using CFD tools. The second phase is to develop an AGS (Active Grille Shutter) prototype and the control of the active system with respect to driving conditions. In the second phase, extensive indoor and road testing done for gathering temperature effects caused by AGS prototype usage. We have started from reviewing the literature and patents which are related to underhood vehicle thermal management and AGS concepts. For flow analysis, aerodynamic underhood CFD model has been generated. All vehicle surfaces and subsystems obtained as CAD data. Engine compartment has been transferred from CAD PLM system and main powertrain components modeled. The engine cooling module (including radiator, CAC, shroud, fan), AIS, exhaust manifold and DPF subsystems have also been added to 3D model. Wraping mesh technique was used for grid generation. Different mesh densities have been applied for engine, body and front grille surfaces. For simulation setup, predefined vehicle speeds have been selected for both AGS- ON and OFF conditions. As results, one can obtain detailed visualizations in pressure, velocity and temperature distributions inside the engine compartment and also streamlines can be visualized for better understanding of the flow characteristics. Ram air pressure contribution has been extracted for underhood components beginning from front grille to exit plane of DPF. For various vehicle speeds the pressure differential can be analyzed for AGS cases. Also the simulation temperature map in engine compartment has been extracted for better understanding of cooling variations. One of the key point of this study is understanding the aerodynamic cooling drag forces by controlling the grill shutter, so this results in fuel saving. EPA's report mentioned 3% or more decreasing in aerodynamic drag (CD) potential of using such active flow systems. AGS systems are already in the market, generally on passenger cars.