Feasibility study of a hybrid ice protection system based on passive removal of residual ice

Aircraft icing is considered a serious weather hazard during flight. Against the background of a more-electric aircraft, electro-thermal systems for ice protection are well-suited to remove in-flight ice accretions from aircraft components. This effort intends to investigate the performance of a wet-running electro-thermal ice protection system and the extent to which surface coatings with low ice adhesion properties enable passive, aerodynamically-induced ice shedding. A heater systematically partitions the ice accreted around the leading edge into an upper and a lower part by melting the ice in the region near the stagnation line. The region of the airfoil aft of the heated region is treated to reduce the adhesion of the ice to the surface and facilitate aerodynamically-induced ice shedding. To demonstrate the feasibility of this approach, a prototype system is tested in a laboratory-scale icing wind tunnel. A numerical model of a NACA 0012 airfoil with a slender thermoelectric heater at the stagnation line is also studied. The aerodynamic forces acting on the residual ice shapes are predicted using a computational fluid dynamics simulation. The resulting loads acting on the ice shape are incorporated into a finite element analysis to determine if the stresses in the ice shape produce delamination from the airfoil surface. The aerodynamic forces required to shed the ice in the unheated area are numerically analyzed and compared to experimental data obtained in a laboratory-scale icing wind tunnel. It can be concluded from both the numerical simulations and the experimental investigations that, except for the warm and mushy glaze ice cases, passive ice shedding due to the aerodynamic forces of the airstream is obtained once the ice layer is thick enough.