De Rosa, Francesco
Electrically heated composite leading edges for aircraft anti-icing applications.
[Tesi di dottorato]
An investigation was conducted in the Aerospace Engineering Department (DIAS) at Federico II University of Naples aiming to evaluate the feasibility and the performance of an electrically heated composite leading edge for anti-icing and de-icing applications. A 283 [mm] chord NACA0012 airfoil prototype was designed, manufactured and equipped with an High Temperature composite leading edge with embedded Ni-Cr heating element. The heating element was fed by a DC power supply unit and the average power densities supplied to the leading edge were ranging 1.0 to 30.0 [kW m-2]. The present investigation focused on thermal tests experimentally performed under fixed icing conditions with zero AOA, Mach=0.2, total temperature of -20 [°C], liquid water content LWC=0.6 [g m-3] and average mean volume droplet diameter MVD=35 [µm]. These fixed conditions represented the top icing performance of the Icing Flow Facility (IFF) available at DIAS and therefore it has represented the “sizing design case” for the tested prototype. An analytical model has been also developed both for the preliminary sizing and test guidance. Running wet and fully evaporative functional modes have been verified both analytically and experimentally with reasonable agreement. A room temperature thermal endurance test has been run for 104 cycles with max thermal load representative of 1.5 times the max temperature experienced within the leading edge in fully evaporative conditions aiming to verify the integrity of the composite laminate after the imposed thermal stress through micrographic inspection. The achieved results, despite obtained under limited icing conditions imposed by the IFF wind tunnel, showed great potentialities for the proposed Icing Protection System named EHCLE (Electrical Heated Composite Leading Edge) which has been constantly working below 60% of its maximum operative temperatures under the given icing conditions and the explored power densities. This potentiality justify the need for future development in a larger scale under more severe icing condition for a final assessment about the applicability of such Icing Protection System to real aircrafts.
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