Reduced Drag and Adequate Cooling For Passenger Vehicles Using Variable Area Front Air Intakes

摘要

Engine cooling systems are usually designed to meet two rare and extreme conditions; driving at maximum speed and driving up a specified gradient at full throttle while towing a trailer of maximum permitted mass. At all other times, the cooling system operates below its maximum capacity with an incurred drag penalty. In this work it is being suggested to design the system using the existing methods and then vary the area of the cooling air intakes to permit the minimum amount of cooling air for adequate engine cooling. A full-size, Australian-made Ford Falcon car (a large modern "family" saloon) was tested at the Monash University Aero-acoustic Wind Tunnel. The cooling air intakes of the vehicle were shielded progressively until fully blocked. Four different possibilities of shielding were investigated with the aim of determining the variation of drag reduction with the shielding method employed. Results from these tests found the optimum method for shielding the cooling intakes for minimizing the drag coefficient was vertical strips. This enables the airflow to be attached smoothly to the body. For a sealed cooling system, the drag reduction achieved was about 7% which corresponds to a prediction of about 2.9% and 1.7% in reducing fuel consumption on highway and urban driving conditions respectively.