Ice accretion presents a major threat for performance and safety of aircraft. Electrothermal Ice Protection Systems present a reliable and flexible alternative to protect critical parts against it. Their main drawback is the high power consumption especially when operating in fully evaporative anti-ice mode. In this work, a genetic algorithm was deployed to optimize the power distribution on the fixed heaters of an electrothermal ice protection system for an airfoil operating in fully evaporative anti-ice mode. The GA is crossover based with a large population and no mutation. The reduction of the overall power consumption is sought. The objective function was constrained with the no-formation of ice in any location of the airfoil. The constraint has been included into the objective function by means of a penalty function. The freezing mass rate is numerically computed by means of the in-house developed code PoliMIce. The best solution encountered, could reduce the power consumption by 13.6% with respect to an intuitive design from literature. Moreover, the optimal layout of heat fluxes reduces the convective losses which are inefficiencies of the system.

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<div class="section abstract"><div class="htmlview paragraph">This study examines the impact of slip in aero-thermal conditions of supercooled large droplets (SLD) produced in an Icing Wind Tunnel (IWT) on the ice accretion characteristics. The study identifies potential biases in the SLD model development based on IWT data and numerical predictions that assume the SLD to be in aerothermal equilibrium with the IWT airflow. To obtain realistic temperature and velocity data for each droplet size class in the test section of the Braunschweig Icing Wind Tunnel (BIWT), a Lagrangian droplet tracking solver was used within a Monte Carlo framework. Results showed that SLDs experience considerable slips in velocity and temperature due to their higher inertia and short residence time in the Braunschweig IWT. Large droplets were found to be warmer and slower than the flow in the test section, with larger droplets experiencing larger aerothermal slips. To examine the impact of these slips, numerical ice accretion simulations were performed on a NACA 0012 airfoil using in-house icing software PoliMIce with realistic droplet slip conditions and ideal equilibrium conditions. Results showed that an increase in velocity slips with larger droplets led to a reduction in the impingement water mass rate and impingement limits. Further, the velocity slip reduced the splashed mass rate estimated by NASA LEWICE and ONERA SLD models. The reduced supercooling of larger droplets reduces the freezing fraction and produces extended runback limits at warmer temperatures ([-1, -5] °C). However, the influence of thermal slip is negligible below -5°C. The study concludes that aero-thermal slips significantly alter the ice accretion characteristics of SLD. It emphasizes the need to consider these slips in IWT data-driven SLD icing model development and subsequent SLD ice accretion simulations.</div></div>

<div class="section abstract"><div class="htmlview paragraph">This work presents a comprehensive numerical model for ice accretion and Ice Protection System (IPS) simulation over a 2D component, such as an airfoil. The model is based on the Myers model for ice accretion and extended to include the possibility of a heated substratum. Six different icing conditions that can occur during in-flight ice accretion with an Electro-Thermal Ice Protection System (ETIPS) activated are identified. Each condition presents one or more layers with a different water phase. Depending on the heat fluxes, there could be only liquid water, ice, or a combination of both on the substratum. The possible layers are the ice layer on the substratum, the running liquid film over ice or substratum, and the static liquid film between ice and substratum caused by ice melting. The last layer, which is always present, is the substratum. The physical model that describes the evolution of these layers is based on the Stefan problem. For each layer, one heat equation is solved. At the ice-water interface, a Stefan condition governs the phase transition. Lastly, mass conservation is imposed. Numerical simulations are compared to reference results, both experimental measurements and numerical simulations for both ice accretion and ETIPS operating in anti-icing and de-icing mode, showing good agreement. A posterior ice shedding analysis is then performed, taking into account the IPS in both anti-icing and de-icing operation modes. The stresses internal to the ice shapes when subjected to the aerodynamic loads are compared with the mechanical properties of ice such as the tensile and adhesion strength. The results show that the de-icing mode is more efficient in causing shedding due to the decrease in adhesion surface and the presence of the under-ice liquid film that tends to break the ice shape.</div></div>