Whilst the primary function of the active grille shutters is to reduce the aerodynamic drag of the car, there are some secondary benefits like improving the warm up time of engine and also retaining engine heat when parked.
In turbocharged IC engines the air is compressed (heated) in the turbo and then cooled by a low temperature cooling system before going into the engine. When the air intake temperature exceeds a threshold value, the engine efficiency falls - this drives the need for the cooling airflow across the radiator in normal operation. Airflow is also required to manage the convective heat transfer across various components in the engine bay for its lifetime thermal durability. Grill shutters can also influence the aerodynamic lift balance thus impacting the vehicle dynamics at high speed. The vehicle HVAC system also relies on the condenser in the front heat exchanger pack disposing the waste heat off in the most efficient way. These requirements of maintaining optimal engine intake charge air temperature, managing condenser heat load, engine bay heat and aerodynamic lift balance pose contradicting challenges in finding the optimal energy balance within the control strategy.
This paper talks about the system engineering approach to the control strategy development of active grille shutters. A combination of 0D (Matlab-Simulink), 1D (GT Suite) and 3D CAE (Dassault Systemes Powerflow) tools were used to define the optimal control strategy. This paper also shows the testing & validation of the thermal results of a Jaguar Land Rover vehicle fitted with active grille shutters, with control strategy optimized to full scale wind tunnel, in a chassis dynamometer environment. The influence of the facility on the test results provides a unique insight into the relation between the facility fan (air handling unit) dimension and the charge air temperature of various different homologation chassis dynamometer emission facilities.