Design and Evaluation of a Conceptual Zero-Emission Truck Model Considering Aerodynamic Efficiency

Emerging zero-emission-powertrain concepts for heavy trucks are providing opportunities to re-shape the vehicle for improved aerodynamics, leading to improved energy efficiency and range resulting from reduced drag. A multi-phase project was initiated to investigate the possibility of improving the aerodynamic efficiency of Class 8 trucks with internal-combustion, battery-electric, and hydrogen-fuel-cell powertrains. Early phases included a scaled-model wind-tunnel test that demonstrated the potential for up to 9% drag reduction from simple shape adaptations, with a follow-up CFD study providing guidance towards further optimization. This paper presents wind-tunnel-test results using a high-fidelity 30%-scale model of the final design concept, with comparison to a conventional North American Class 8 truck with a modern aerodynamic package and identical wheelbase. The study included the investigation of the new model along with individual parts such as air dams, underbody panels, grill/cooling-flow configurations, mirrors, wheel fairings, cab extenders, etc. The new model provided a 16% drag reduction compared to the conventional model with the same trailer configuration. To examine the potential for a low-drag tractor-trailer combination, the new tractor concept was paired with a low-drag-trailer concept, showing up to a 42% drag reduction compared to the conventional tractor with a standard box-van trailer. This configuration provided a wind-averaged drag coefficient of around 0.33 which was nearly insensitive to crosswinds. Specifically, when considering zero crosswind (lower yaw angles), about a 40% drag reduction was observed, while at higher crosswinds (15° yaw angle), up to 56% drag reduction was observed.