Heavy commercial vehicles due to their un-streamlined body shapes are aerodynamically inefficient due to higher fuel consumption as compared to passenger vehicles. The rising demand and use of fossil fuel escalate the amount of carbon dioxide emitted to the environment, thus more efficient tractor-trailer design becomes necessary to be developed. Fuel consumption can be reduced by either improving the driveline losses or by reducing the external forces acting on the truck. These external forces include rolling resistance and aerodynamic drag. When driving at most of the fuel is used to overcome the drag force, thus aerodynamic drag proves an area of interest to study to develop an efficient tractor-trailer design. Tractor-trailers are equipped with standard add-on components such as roof defectors, boat tails and side skirts. Modification of these components helps reduce drag coefficient and improve fuel efficiency. The objective of this study is to determine the most effective geometry of trailer add-on devices in semi-truck trailer design to reduce the drag coefficient to improve fuel efficiency and vehicle stability.
The methodology consisted of CFD analysis on Mercedes Benz Actros using ANSYS FLUENT. The simulation was performed on the tractor-trailer at a speed of 30m/s. The analysis was performed with various types of add-on devices such as side skirts, boat tail and vortex generators. From the simulation results, it was observed that addition of tractor-trailer add-on devices proved beneficial over modifying trailer geometry. Combination of add-on devices in the trailer underbody, rear and front sections was more beneficial in reducing drag coefficient as compared to their individual application. Improving fuel efficiency by 17.74%. Stability of the tractor-trailer is improved due to the add-on devices creating a streamlined body and reducing the low-pressure region at the rear end of the trailer.