An Optimized Hybrid Strategy for more Efficient Electrothermal Anti-Icing of UAV Rotors

An experimental study was conducted in Iowa State University’s Icing Research Tunnel (ISU-IRT) to test an optimized rotor-integrated electrothermal heating system (i.e., RIHS) for a wide range of icing conditions (i.e., glaze, mixed and rime ice). The optimized RIHS consists of rotor blades equipped with a minimized leading edge heating film, complemented by the application of a superhydrophobic (SHS) coating across the entirety of the blades' surfaces. To verify the effectiveness of the optimized RIHS, its anti-icing capabilities are compared to baseline tests of bare blades, blades coated with an SHS coating only and to rotor blades equipped with a complete surface heating film. During the tests, a “phase-locked” high-speed imaging technique was employed to reveal the instantaneous and important features of the anti/de-icing capabilities of the rotor-integrated electrothermal heating system. Moreover, the aerodynamic forces generated by the rotor model and its motor power consumption were measured real-time to quantify the benefits of employing the anti/de-icing heating system of this work. Results show that the SHS fails as a stand-alone anti-icing strategy since ice was seen to accrete on the rotor blade in a comparable fashion to the baseline hydrophilic blades. Moreover, rime ice accumulation over SHS coated blade showed delayed ice shedding, indicating a stronger ice adhesion to the surface. The major benefit of using the SHS coating was highlighted when used as part of a hybrid anti/de-icing strategy where the optimized RIHS with minimized leading-edge heating and SHS surface treatment showed excellent ice protection with up to 40% less energy requirements compared to the basic RIHS with hydrophilic surface properties.