Fuel Savings from Truck Aerodynamic Drag Reducers and Correlation with Wind-Tunnel Data

Abstract

A 9347 km (5809 mi) cross-country fuel economy experiment was conducted to demonstrate typical fuel savings that can be obtained using drag-reducing devices on tractor-trail er trucks, and to ascertain the degree of correlation of the experimentally determined fuel savings with the fuel savings that could be predicted using data from drag reduction experiments on models in a wind-tunnel. Three trucks were used in the experiment. One truck was equipped with a commerically available wind deflector/vortex stabilizer system, another was equipped with a prototype streamline fairing/gap seal system developed at the University of Maryland, and the remaining vehicle was operated without any drag-reducing devices in order to obtain a basis from which to determine the fuel savings. The fuel savings per unit distance that resulted from use of the commerical drag reducing system was 0.029±.006 liter/km (0.012±.002 gal/mi), while that realized with the University-of-Maryland-developed prototype system was 0.057±.003 liter/km (0.024±.001 gal/mi). An analysis of the conditions under which these results were obtained indicated that they were conservative estimates of the fuel savings that would be realized with long-term operating of the vehicles and devices used in the experiment. Fuel savings predictions were performed using wind-tunnel drag reduction data, and relative airspeed and yaw angle data continuously measured in the fuel economy experiments. The measured fuel savings due to the commercial system was 75 ± 15% of the predicted value, and that due to the University of Maryland system was 78 ±4% of the predicted value. The differences obtained appear related to the nonsimulation of wind turbulence in the wind-tunnel experiments.