Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results

Paper #:
  • 2018-01-0740

Published:
  • 2018-04-03
Abstract:
The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body; this airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag, known as cooling interference drag. Cooling drag generally contributes up to 10% of total vehicle drag and is difficult to predict, due to influences from many direct (engine bay airflow path) and indirect (cooling interference airflow path) factors. Active grille shutters (AGS) are a commonly used mechanism to influence the engine bay airflow drag contribution of cooling drag. For certain driving conditions the AGS system can restrict airflow from passing through the heat exchangers which significantly reduces cooling drag. The difference in drag between AGS vanes being open and closed is referred to as AGS drag. Chin spoilers are components that lie within cooling interference airflow paths for many vehicles and can be used/designed to affect cooling drag. This study focuses on understanding the influence of the chin spoiler on cooling and AGS drag of a production level F-150. The chin spoiler variables tested were height and curvature, all experiments were conducted in both static and moving ground wind tunnel conditions at 80 MPH between yaw angles of +/-7°. In addition to overall vehicle drag coefficients, surface pressures at discrete locations and cooling pack airflow rates were measured to provide better insight into the internal and external airflow behaviour.
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