Experimental study on the icing hazards over the propeller of a Low-Altitude flight UAV under changeable liquid water content environment

Abstract

Low-altitude aerial operations frequently encounter rapidly varying ground meteorological conditions, leading to potential hazards for unmanned aerial vehicles (UAVs). To address this concern, a comprehensive experimental study was conducted to examine the icing hazards on UAV propellers, specifically in continuous and intermittent icing environments. The experiments were conducted in a specialized icing facility at Shanghai Jiao Tong University, designed to replicate flying conditions typical of UAVs, including continuous icing and intermittent precipitation scenarios. The findings reveal that, under identical durations of icing exposure, the intermittent icing environment resulted in more than 15% accumulation of ice mass on the propeller. This ice accretion led to a significant reduction in thrust coefficient, diminishing to less than 10% of its designed operational point, in contrast to a thrust coefficient of more than 16% observed under continuous icing conditions. Consequently, these results indicate that intermittent precipitation presents a greater hazard to UAV operations. Further analysis suggests that the disparity in heat transfer mechanisms, where the cold air and the propeller substrate have a prolonged interaction with the released latent heat, contributes to differing ice shape evolution patterns. This phenomenon resulted in a heightened local water collection rate during intermittent icing episodes, attributed to a reduced occurrence of ice and droplet shedding. As a consequence, there was a notable accumulation of larger ice formations at the leading-edge region of the propeller, with an increase of over 33% in the windward contact area across 95% of the spanwise distribution compared to baseline conditions. The presence of such icicles is expected to exacerbate local water collection rates, thereby leading to even more severe icing events for UAVs before the onset of ice shedding.