UAM Icing: Ice Accretion Experiments and CFD Icing Simulations on Rotors for eVTOL Unmanned Aircraft 2023-01-1391

Urban air mobility (UAM) is a fast-growing industry that utilizes electric vertical take-off and landing (eVTOL) technologies to operate in densely populated urban areas with limited space. However, atmospheric icing serves as a limitation to its operational envelope as in-flight icing can happen all year round anywhere around the globe. Since icing in smaller aviation systems is still an emerging topic, there is a necessity to study icing of eVTOL rotors specifically. Two rotor geometries were chosen for this study. A small 15-inch rotor was selected to illustrate a multirotor UAV drone, while a large 80-inch rotor was chosen to represent a UAM passenger aircraft. The ice accretion experiments were conducted in an icing wind tunnel on the small 15-inch rotor. The icing simulations were performed using FENSAP-ICE. The ice accretion simulations of the 15-inch rotor sections at –5 °C show a large, rather streamlined ice shape instead of the expected glaze ice characteristics. At –15 °C the numerical ice accretion presents the typical rime ice shape. The results of the 80-inch rotor simulation present more varied ice shapes, which could indicate higher sensitivity towards the icing condition. Ice horns formed at temperatures close to freezing and the flow separation aft of the ice led to significant aerodynamic penalties. The 3D ice accretion simulation of the 80-inch rotor shows discrepancies with the 2D results as it does not predict ice accretion at the outer region of the blades at – 15 °C. This could be due to the higher stagnation temperature, increased friction, and three-dimensional crossflows preventing ice accumulation. The performance degradation simulations show that ice accretion causes significant aerodynamic penalties, especially in cases where horn ice accretion forms. Finally, the anti-icing loads required to mitigate ice accretion thermally were calculated. Both rotors require high power consumption for a fully evaporative IPS design.