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Many approaches exist today that employ hot-air from aircraft compressor bleed for anti-icing critical aircraft surfaces. This paper introduces and numerically analyzes the novel application of an inner or etched channel to augment heat transfer from a hot-air jet impinging on a curved surface representing the inner surface of an aircraft wing’s leading edge or slat. The study shows that proper positioning, geometry, and flow characteristics of a channel along the inner surface of the leading edge can significantly enhance heat transfer, boost the anti-icing system performance, and greatly enhance flight safety during critical icing weather conditions. Commercially available CFD software, ANSYS Fluent is used to model and analyze the effect of different geometric and flow parameters typical of those found in small to medium category commercial transport aircraft to help determine the optimum arrangement. These parameters include: (1) jet nozzle height-to-slot diameter ratios from 4 to 8, (2) channel width-to-slot diameter ratios from 0.4 to 1.8, and (3) inner-channel inlet location angles from 10° to 60°. Each configuration resulting from a combination of the above parameters was simulated at Reynolds numbers based on jet-slot diameter of 30,000, 60,000, and 90,000. Empirical relations based on available experimental data are used to validate the results. The main findings of the study reveal that the jet height-to-slot diameter ratio of 6, inner channel height-to-slot diameter ratios of 1.8, and inner-channel inlet angular locations of 10° combination resulted in the highest heat transfer at all Reynolds number as well as higher at increased Reynold numbers. Graphical abstract Description of figures: (a) RAE 2822 airfoil with a modified leading edge to incorporate, (b) a typical wing leading slat, (c) internal layout of the piccolo tube inside a typical edge slat (Courtesy of Bombardier Aerospace), (d) numerical simulation of heat transfer from the hot-air jet from a piccolo tube impinging on the inner surface of the slat, and (e) numerical model with etched channel (novel idea) for enhanced heat transfer being investigated in current study.

In this study, an aircraft icing diagnosis and forecasting method is constructed and hindcast for 25 collected spring icing cases over Eastern China based on two commonly used aircraft icing diagnostic methods (hereinafter referred to as the IC index method and the TF empirical method, respectively) and ERA5 reanalysis data as the atmospheric environmental field for icing occurrence. The spatial and temporal distribution characteristics of aircraft icing accumulation occurrence over typical cities at different latitudes in China are calculated separately, and the spatial and temporal distribution of icing accumulation areas over Xinchang, Zhejiang Province in China during one case of cold air activity is simulated. Accordingly, several application scenarios for the application of methods to forecast aircraft icing accumulation are proposed. The results indicate that among the selected icing cases, the diagnosis accuracy of the IC index method and the TF empirical method is 80% and 92%, respectively. The TF empirical method takes into account the effects of aircraft flight speed and dynamic warming, and shows better correlation with ice water particle concentration and cloud cover in medium and low clouds. However, the predicted icing accumulation intensity predicted by the TF empirical method is not accurate enough without the real flight speed of the aircraft, and there are more empty forecasts above 400 hPa. In practical applications, both the IC index method and the TF empirical method can effectively identify the icing-prone pressure levels and time periods and forecast the distribution of icing accumulation intensity at high pressure levels for a given station.

Considering the effect of icing on aircraft control performance, this paper proposes an adaptive dynamic inverse ice tolerance control method based on piecewise constant. A control allocation algorithm is introduced to compensate for the change of control surface performance caused by icing. This method can achieve satisfactory disturbance estimation accuracy under a given sampling time, and thus ensure a closed-loop system error within an acceptable range. The proposed design method is applied to the design of a flight control law for a transport aircraft, aiming to solve the problem of ice-tolerant flight control, reduce the influence of icing conditions on controllability and safe flight of the transport aircraft, and thus improve the flight quality of the transport aircraft. The simulation results are verified under the influence of both standby ice type and failure ice type, and the interference effect on aircraft aerodynamic parameters is further added. The simulation results show that adaptive dynamic inverse control based on piecewise constant can overcome the influence caused by icing and aerodynamic parameter interference, achieve accurate tracking of command, and provide excellent fault tolerance and robustness, which ensures that the transport aircraft can achieve the desired control performance and safe flight capability.

An unsteady tightly-coupled icing model is established in this paper to solve the numerical simulation problem of unsteady aircraft icing. The multi-media fluid of air and droplets is regarded as a single medium fluid with variable material properties. Taking the droplet concentration as the phase parameter and the droplet resistance coefficient as the interphase force, the mass concentration distribution of the droplet is obtained by solving the Cahn–Hilliard equation. Fick’s law is introduced to improve the Cahn–Hilliard equation to predict the droplet shadow zone. On this basis, the procedure of the unsteady numerical simulation method for aircraft icing is established, including grid generation, the dual-time-step method to realize the unsteady calculation of the air and droplet tightly-coupled mixed flow field, and the improved shallow water icing model. Finally, through the comparative analysis of numerical examples, the effectiveness of the new model in predicting the droplet impact characteristics and the droplet shadow zone are verified. Compared with other icing models, the ice shapes predicted by the unsteady tightly-coupled model were found to be the most consistent with the experiments. In the icing comparison conditions in this manuscript, the prediction accuracy of the ice thickness at the stagnation point of the leading edge was up to 35% higher than that of LEWICE.

When icing, aerodynamic surfaces of the aircraft, negative changes in the impact of the air flow on them occur, which leads to a noticeable drop in wing lift, a decrease in the efficiency of the rudders, a decrease in the aircraft and loss of control. In order to optimize the complex of technological equipment for anti-icing treatment of the aircraft, the necessary studies of materials and methods of anti-icing treatment of aircraft were carried out, based on the KNO-AERO-MA complex, designed for processing (washing, anti-icing protection) of the outer surfaces of aircraft, due to the existing pumping equipment in the system of collecting and returning the spent solution. The essence of the filtering technology is to clean solutions from harmful impurities through a special porous medium, the so-called filter. The created simplified model of a high-speed pressure vertical filter made it possible to study one or more filter links of the filter column. According to the research results, in order to optimize the technological equipment complex during aircraft anti-icing treatment, in the system of collecting and returning spent solutions for repeated anti-icing treatment of aircraft, it is recommended to use a highspeed pressure vertical granular filter. The introduction of such a system will allow servicing several aircraft simultaneously, significantly reduce the cost price and improve the environmental friendliness of this technological process. Keywords: icing, aircraft aerodynamic surfaces, optimization of the technological equipment complex, aircraft anti-icing treatment, system of collecting and returning spent solution, filtration technologies, high-speed pressure vertical granular filter, reduce the cost price, improve the environmental friendliness of the process.

The occurrence of aircraft icing can significantly affect flight performance. One of the most important aspects in the study of anti-icing technology for aircraft is the distribution of overflow water. Owing to the external airflow pressure, shear stress, and surface tension, the water film breaks up to form steady rivulets. Experiments on NACA0012 airfoil surfaces were conducted based on an open straight-flow and low-speed wind tunnel. Simultaneously, an engineered three-dimensional rivulet model considering the surface roughness was established based on the energy-minimum principle. A comparison between the simulation and experimental results shows that the errors in the water film breakup location and the flow velocity of rivulets are less than 20%, and the errors in the spacing and width of rivulets are less than 40%. In addition, the effects of surface temperature and uniform roughness on water film breakup were investigated. Furthermore, the rivulet model was applied to the numerical calculation of the thermal performance of hot-air anti-icing systems. The simulations reveal that the uniform roughness of the wing surface causes the water film to break earlier. As the surface roughness increases, the thickness, spacing, and width of the rivulets increase, and the rivulet flow velocity decreases.

Icing on an aircraft is the cause of numerous adverse effects on aerodynamic performance. Although the issue was recognized in the 1920s, the icing problem is still an area of ongoing research due to the complexity of the icing phenomena. This review article aims to summarize current research on aircraft icing in two fundamental topics: icing physics and icing mitigation techniques. The icing physics focuses on fixed wings, rotors, and engines severely impacted by icing. The study of engine icing has recently become focused on ice-crystal icing. Icing mitigation techniques reviewed are based on active, passive, and hybrid methods. The active mitigation techniques include those based on thermal and mechanical methods, which are currently in use on aircraft. The passive mitigation techniques discussed are based on current ongoing studies in chemical coatings. The hybrid mitigation technique is reviewed as a combination of the thermal method (active) and chemical coating (passive) to lower energy consumption.

New results of aircraft icing are obtained. New mathematical models of physical phenomena are formulated. Original construction of adaptive wing was invented, developed and prototypes were built. New algorithm of aircrafts’ surface with nanorelief are developed. Parametric studies of aircraft icing peculiarities were carried out.

Antifreeze proteins from polar fish species are remarkable biomacromolecules which prevent the growth of ice crystals. Ice crystal growth is a major problem in cell/tissue cryopreservation for transplantation, transfusion and basic biomedical research, as well as technological applications such as icing of aircraft wings. This review will introduce the rapidly emerging field of synthetic macromolecular (polymer) mimics of antifreeze proteins. Particular focus is placed on designing polymers which have no structural similarities to antifreeze proteins but reproduce the same macroscopic properties, potentially by different molecular-level mechanisms. The application of these polymers to the cryopreservation of donor cells is also introduced. Ice crystal growth is a major problem in cell and tissue cryopreservation for transplantation, transfusion, icing of aircraft wings and many other applications. Here the authors review the emerging field of synthetic macromolecular mimics of antifreeze proteins that can be used overcome such problems.

Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of flight due to the damage of aerodynamic shape. This review article provides a comprehensive understanding of the preparation and anti-icing applications of the superhydrophobic coatings applied on the surface of aircrafts. The first section introduces the hazards of aircraft icing and the underlying formation mechanisms of ice on the surface of aircrafts. Although some current anti-icing and de-icing strategies have been confirmed to be effective, they consume higher energy and lead to some fatigue damages to the substrate materials. Considering the icing process, the functional coatings similar to lotus leaf with extreme water repellency and unusual self-cleaning properties have been proposed and are expected to reduce the relied degree on traditional de-icing approaches and even to replace them in near future. The following sections mainly discuss the current research progress on the wetting theories of superhydrophobicity and main methods to prepare superhydrophobic coatings. Furthermore, based on the bouncing capacity of impact droplets, the dynamic water repellency of superhydrophobic coatings is discussed as the third evaluated parameter. It is crucial to anti-icing applications because it describes the ability of droplets to rapidly bounce off before freezing. Subsequently, current studies on the application of anti-icing superhydrophobic coatings including the anti-icing mechanisms and application status are introduced in detail. Finally, some limitations and issues related to the anti-icing applications are proposed to provide a future outlook on investigations of the superhydrophobic anti-icing coatings.