An Automotive Front-End Design Approach for Improved Aerodynamics and Cooling

With the increasing emphasis on and importance of aerodynamics on vehicle fuel economy and handling, conservative approaches to sizing front-end cooling openings based on projected radiator area need to be replaced by a performance-based method. The method would not only allow more flexibility in front-end styling, but would enable the design of the grille, cooling hardware and vehicle heat rejection requirements to be based on the cooling performance of the total vehicle. The reductions in cooling drag and front lift from smaller, but more functional, grille openings would improve vehicle fuel economy and handling.

A performance-based front-end design approach is described in the paper along with some selected experimental results. The method is based on an experimental technique for simultaneously measuring the total radiator airflow and vehicle aerodynamic performance in an aerodynamic wind tunnel. The measured cooling airflows are correlated to vehicle cooling performance and are shown to explain over 95% of the physical variation in the measured results. Based on this correlation, airflow targets for the front-end design of advanced models can be established with confidence. An air-side heat rejection analysis of vehicle cooling test data from three radiators yields very consistent heat rejection results. Grille open area as a design parameter is shown to be a poor predictor of ram airflow and cooling drag. There is need for a minimum interference technique for measuring coolant-side radiator/condenser heat rejection during a vehicle test, and more work needs to be done relative to underhood component cooling requirements.