Rapid Blade Shape Optimization for Contra-Rotating Propellers for eVTOL Aircraft Considering the Aerodynamic Interference

Abstract

The rising interest in the evolvability of electric vertical takeoff and landing (eVTOL) promises substantial potential in the field of urban air mobility (UAM). Challenges in energy storage density and geometry restriction both emphasize the propeller efficiency for endurance and takeoff weight, whereas the contra-rotating propellers (CRP) advantage is balancing high thrust and efficiency over a single propeller. The aim of this paper is twofold: (i) to present a novel rapid CRP blade shape optimization framework and (ii) to study the impact of the dual propellers revolution speed allocations on the overall CRP power efficiency. The core of the framework is the blade element momentum theory (BEMT)-based blade shape optimization considering the wake effect of the upper propeller by the rotational CFD (computational fluid dynamics) actuator-disc simulation method. The results show that for the same thrust, the optimized CRP at the equal revolution speed is superior to the original (upper-lower-identical) one by 5.9% in thrust-to-power ratio. The overall efficiency can be additionally lifted by 5.3% when the dual propellers share similar torques. By excluding the integral propeller CFD simulation and empirical parameters estimation, the framework enables the swift obtaining of an optimized CRP scheme while maintaining robustness as well.

Aerodynamic Performance and Numerical Analysis of the Coaxial Contra-Rotating Propeller Lift System in eVTOL Vehicles

“…Based on this advantage, coaxial counter rotating propellers have been widely used in the field of unmanned aerial vehicles (UAV) [8,9]. As the core component of the lift system for eVTOL vehicles, the aerodynamic performance of coaxial counterrotating propellers plays a decisive role in the overall performance and safety of eVTOL vehicles [10]. Therefore, a deep understanding and accurate simulation of the aerodynamic interactions between coaxial counter-rotating propellers and the precise evaluation of their aerodynamic performance are crucial factors that need to be considered in the design process of eVTOL vehicles.…”

Aerodynamic optimization of eVTOL rotor profiles

“…Qiao et al [5] presented a rapid contra-rotating propellers (CRP) blade shape optimization framework and studied the impact of the dual propellers revolution speed allocations on overall CRP efficiency. Their investigations were based on the blade element momentum theory (BEMT).…”