Feasibility Study of a Hybrid Ice Protection System

Abstract

A key design factor impacting the use of electrical power to drive aircraft systems and subsystems is energy efficiency. With the design of an all-electric, hybrid ice protection system, energy consumption can be reduced to a large extent. The hybridization is achieved through an intentional partitioning of the ice at the stagnation line by melting via surface heating and ice shedding in the unheated regions of the airfoil surface via an electromechanical deicing system based on piezoelectric multilayer actuators. To further reduce energy consumption, the adhesion forces between the ice and the airfoil surface can be reduced using an ultrasmooth, nanostructured surface with water- and ice-repellent properties that encourages ice shedding. Experimental investigations, performed in a laboratory-scale icing wind tunnel for a small-scale configuration, reveal that the hybrid approach for ice protection reliably sheds the ice accreted on the airfoil surface. Compared with an all-thermoelectric system for ice protection investigated in the same icing wind tunnel facility using identical test conditions, the hybrid approach was demonstrated to reduce power consumption up to 91%. Beyond the laboratory tests, numerical simulations of the hybrid strategy analogous to the one used for the experiments are performed. The time history of the residual ice shapes aft of the heated region is simulated using the ice accretion prediction software LEWICE2D for a wet-running anti-icing subsystem. Finite element analyses of the effects of the piezoelectric actuators are then performed using Abaqus to investigate the ice-shedding capability in the unheated regions of the airfoil surface. The numerical results show that the variation in the different ice shapes affects the stiffness of the model. It becomes obvious that the critical threshold for ice shedding, that is, the stiffness that determines whether residual ice delaminates from the airfoil surface, is affected to a minor extent by the interfacial area and predominantly by the thickness of the ice layer. Further, the simulation results correlate well with experimental results obtained in the icing wind tunnel. It can be concluded that reliable operation of the hybrid system for ice shedding can be guaranteed when using a harmonic sweep excitation able to excite the structure at its resonance.