Experimental Investigation of Simulated Horn Ice Shapes on Small-Scale Propeller Performance Degradation

This study presents an experimental investigation of horn ice accretion on propeller performance. A small-scale propeller was designed with the aid of an analytical Blade-Element Momentum method, to operate within the wind tunnel envelope. Simulated horn ice shapes were applied to the blade surface, and the effects of horn geometry were assessed through a parametric variation of its main geometric features, such as height, surface position and radial distribution. Reynolds and Mach numbers effects on performance were also studied. Wind-tunnel tests revealed that ice shapes located at leading-edge to lower surface positions showed unexpected results presenting a greater thrust and comparable, or even lower, torque than the clean propeller. A leading-edge flap and an effective chord increase effects were identified as responsible for such outcomes. The ice shapes located on the upper surface caused the greatest performance degradation. The effects of ice surface position were observed to be directly proportional to the ice shape height. Both clean and iced configurations exhibited significant variation in performance coefficients with changes in rotational speed, attributed to the low reference Reynolds numbers associated to the small-scale tests and the limited rotation speeds imposed by the structural constraints of the resin printed propellers. Consequently, extrapolating these results to full-scale commercial propeller performance is not recommended.