Self‐Limited Ice Formation and Efficient De‐Icing on Superhydrophobic Micro‐Structured Airfoils through Direct Laser Interference Patterning

Abstract

Surface contamination by ice poses a hazard to industries ranging from power transmission to transportation by ground, sea and air. The aviation industry is particularly affected by icing phenomena that manifest as a reduction in fuel efficiency and compromised aerodynamic lift, which can impair flight safety. [1] Consequently, there is a worldwide scientific effort to understand the physics of icing, aiming to develop effective and efficient anti-icing and de-icing strategies. [2] Icing can occur while aircraft are on the ground or in the air. On the ground, when freezing precipitation contaminates the surfaces of an aircraft, safety protocols delay that aircraft's scheduled flight. In fact, contamination necessarily needs to be removed since it alters aerodynamic properties and, like on a snow-covered car, ice fragments can be sheared off by aerodynamic drag and fly into the engines. A typical ground de-icing operation consists in directly spraying an aircraft with a mixture of warm water and glycol. [3] Generally, ice contamination in the air is caused by the impact of supercooled water droplets found in clouds. Depending on several conditions, droplets may either stick to a surface at the point of impact or flow along the surface in the direction of airflow. In the latter case they form a thin film of water, where surface tension forces them into rivulets. [1,4] While fixed-wing aircraft cruise at altitudes above where icing can occur, helicopters operate at altitudes where supercooled water droplets are known to occur (temperature range between −40 and 0 °C). [5] Aviation safety authorities demand to avoid flying into known icing conditions and, as an additional precaution, they enforce through certification, the equipment of ice protection systems (IPS) to all commercial aircraft. [6] IPS can provide either anti-icing, de-icing, or both countermeasures. [1,7] Thermal anti-icing describes a condition where all impinging water droplets are evaporated by a high-temperature surface. A de-icing countermeasure is one where ice is removed from a surface once it has reached a subjectively critical size. [7] Commercial airliners, for the most part, are equipped with thermal IPS that use hot air drawn from the compressor of their turbofan engines, which is diverted to critical surfaces Forward facing aerodynamic surfaces such as rotors and wings are susceptible to ice build-up when exposed to atmospheric icing conditions. If not removed, accumulated ice on aircraft surfaces affects aerodynamics or rotation balance, which can ultimately lead to increased fuel consumption, reduced operational performance and to potentially hazardous situations. Laser surface structuring is proposed as an alternative technology to coatings for achieving icephobic properties and support anti-icing and de-icing processes on aerodynamic surfaces. However, to authors' knowledge, no study available in the literature reports on the icing behavior of microtextured curved aerodynamic profiles and the effect of the laser surface treatment on the...

Icephobic Performance of Multi-Scale Laser-Textured Aluminum Surfaces for Aeronautic Applications

“…A novel approach to target these objectives are micro-textured functional surfaces with icephobic properties. An icephobic surface has per definition the following properties: (i) they delay the solidification time of the water or reduce ice accretion while the heterogeneous nucleation is hindered [ 20 ] and (ii) ice removal is promoted due to low adhesion strength between ice [ 21 , 22 ]. Superhydrophobic coatings on aluminum have demonstrated a remarkable potential to tackle the challenge of icing aircraft surfaces [ 23 ].…”

Laser Fabrication of Anti-Icing Surfaces: A Review

“…Recently, for the first time, Alamri et al [ 14 ] reported on the de-icing behavior of the Direct Laser Interference Patterning of curved aerodynamic profiles, namely airfoils, combined with electrothermal heating used for ice protection systems. After the laser treatment, the airfoil was treated with MecaSurf, a commercial product used to reduce the surface free energy to make it strongly superhydrophobic, with a WCA exceeding 150°, and a roll-off angle < 15.…”

“…In the latter case, the impact of supercooled water droplets found in clouds, depending on atmospheric conditions, may stick to the surface, creating a dangerous ice layer. Therefore, the overall recommendation of the safety authorities is to strengthen the ice protection systems (IPS) to all commercial aircraft [ 14 ]. These protection systems can be classified into two groups: anti-icing systems, which aim to prevent ice formation, and de-icing systems, which aim at the removal of already-accumulated ice or frost from a surface.…”

Effect of Surface Structure Complexity on Interfacial Droplet Behavior of Superhydrophobic Titanium Surfaces for Robust Dropwise Condensation

“…Humans often turn to nature for inspiration when developing new technologies. The lotus leaf, which provided a template for researchers studying superhydrophobic surfaces, is a classic example and has been referenced in many applied studies on superhydrophobicity [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. The superhydrophobic surface property is determined by the contact angle.…”