Improved Pneumatic Aerodynamics for Drag Reduction, Fuel Economy, Safety and Stability Increase for Heavy Vehicles 2005-01-3627

Aerodynamic drag is the major component of Heavy Vehicle (HV) resistance at typical highway speeds, and thus strongly impacts related fuel economy because horsepower required to overcome this drag increases as the cube of vehicle speed. In an ongoing drag-reduction program for HVs conducted for the US Department of Energy (DOE), Georgia Tech Research Institute (GTRI) has been applying advanced new aerodynamic technology previously developed for aircraft. This technology uses tangential blowing to reduce the drag generated by these bluff-based high-drag vehicles, particularly the trailer. Drag reduction can be accomplished by this blown concept without moving surfaces, and it also offers the potential to increase drag for braking if needed and to overcome both increasing drag and destabilizing side forces due to large side winds and gusts. Wind-tunnel evaluations of baseline unmodified HVs and of the latest blown Pneumatic Heavy Vehicle (PHV) configurations have confirmed drag coefficient reductions of up to 31% below the baseline due to these new pneumatic configuration improvements. These tunnel results have led to a recent full-scale on-track SAE Type-II fuel economy evaluation of this concept installed on a Volvo-Great Dane test vehicle combo. Test-track results have shown an 11-12% Fuel Economy Increase (FEI) for this blown vehicle, which is reduced somewhat to 8-9% FEI once the fuel to drive the proof-of-concept onboard test blowers is included. Since 1% FEI represents approximately 200 million gallons of diesel fuel saved if employed by the entire US HV fleet, optimistic promise is shown by this data. These model- scale and full-scale results are presented in this paper, as are experimental results showing aerodynamic braking and side-wind control resulting from slight modifications to the blown system applied to advanced PHV configurations.