Abstract
Today’s design of tractor-trailers is significantly influenced by legislative boundary conditions regarding the overall vehicle dimensions. This fact in combination with the target of high transportation efficiency leads to brick-shaped vehicle outer geometries. Thus, investigations of aerodynamic optimization of commercial vehicle trailers are predominantly restricted to detail measures. This publication treats the aerodynamic optimization by application of general modifications at the outer contour of tractor-trailers with the target of a drag resistance reduction and thus a potential reduction of fuel consumption. Main objective of this study was to increase the transportation efficiency of commercial vehicles within present legislative boundaries. The research work is based on a generic, virtual 3D-CAD semi-trailer truck, which represents the characteristics of market-typical vehicles and serves as a basis for several modifications. In an aerodynamics study all geometrical modifications at the virtual reference vehicle are investigated and assessed by 3D-computational fluid dynamics simulations (CFD). The fuel consumptions of the aerodynamic optimized tractor-trailer versions were calculated in longitudinal vehicle dynamics simulations. Considering the goal of conformity with actual legislative boundaries and the simultaneous objective to increase the transportation efficiency of the vehicle arrangement, a novel solution was designed, which enables an application of aerodynamic optimized shapes at existing trailer body structures. As a result of the present work, different aerodynamic optimization measures are assessed and evaluated in comparison with a reference vehicle under consideration of the transportation volume. The research work demonstrates the big potential of aerodynamic optimization by application of general measures at the trailer outer contour under compliance with legislative boundary conditions. To prevent losses of payload space, a new approach has been developed to support high transportation efficiency. This approach enables a reduction of aerodynamic drag and the provision of required transportation volume at the same time by implementation of a variable outer shape of the trailer rear end. Considering the large number of journeys with reduced or without payload, this leads to the cognition, that the overall transportation efficiency can be increased significantly by application of a variable trailer body.
KEYWORDS aerodynamics optimization, commercial vehicle, transportation efficiency, variable trailer body, 3D-CFD