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

Emerging zero-emission-powertrain concepts are providing opportunities to re-shape heavy trucks for improved aerodynamic performance. To investigate the potential for energy savings through aerodynamic improvements, with a goal to inform operators and regulators of such benefits, a multi-phase project was initiated to design and evaluate aerodynamic improvements for Class 8 tractor-trailer combinations. While the focus was battery-electric and hydrogen-fuel-cell powered trucks, improvements for internal-combustion powered trucks were also examined. Previously-reported activities 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 a new aerodynamic tractor concept, with comparison to a conventional North American Class 8 tractor with a modern aerodynamic package and identical wheelbase. The study included testing of the new tractor concept along with individual parts such as air dams, under-body panels, grill/cooling-flow configurations, mirrors, wheel fairings, cab extenders, etc. The battery-electric variant of the new tractor provided a 16% drag reduction compared to the conventional truck model when using the same trailer configuration. When paired with a low-drag-trailer concept, the new tractor-trailer combination demonstrated up to 41% drag reduction compared to the conventional tractor with a standard box-van trailer. This configuration is shown to be nearly insensitive to crosswinds with a wind-averaged drag coefficient of 0.34. Examining additional cooling-flow configurations necessary for hydrogen-fuel-cell trucks showed up to 3% increase in drag associated with the extra cooling drag. Additionally, the new tractor-shaping concept applied to a conventional internal-combustion-powertrain arrangement generated 8% drag reduction compared to the conventional tractor.