Aerodynamic drag reduction and energy-saving performance of road vehicles via motor-driven vertical-axis wind turbine

Aerodynamic drag dominates energy consumption for highway vehicles – especially square-back heavy vehicles – at high speeds, so improving aerodynamic efficiency is critical for energy saving and emissions reduction. This study proposes and validates a novel strategy: integrating a motor-driven drag-type vertical-axis turbine at the vehicle’s front roof edge as a form of ’moving-surface boundary-layer control’ to suppress flow separation. Our experimental investigation employed a GM bus model to systematically evaluate the effects of key turbine parameters – including placement, rotation direction, and blade orientation – on aerodynamic drag. The methodology integrated force measurements, surface pressure mapping, and particle image velocimetry (PIV) across two wind tunnel facilities. Results show that the front-edge placement with anticlockwise rotation performs best, reducing the drag coefficient by 18.5% at a motor-controlled tip speed ratio (TSR) of 1.12 and maintaining a consistent 13%–15% reduction over the typical TSR range. The mechanism involves suppressed front-edge separation, a contracted wake vortex, and improved base-pressure recovery. For a full-scale vehicle at 90 km/h, the system saves 12.06 kW traction power while requiring only 1.8 kW to drive the turbine, ensuring a positive net energy balance. Combining low power demand, self-powering potential, and easy integration with vehicle control systems, the approach shows strong engineering value and scalability for coaches, tractor-trailers, rail, and other streamlined vehicles.