Ice Protection System Research Articles

Considering Thermal Diffusivity as a Design Factor in Multilayer Hybrid Ice Protection Systems

Icing is a major problem that affects the aeronautical sector, which is forced to use anti- and de-icing systems to ensure flight safety. The currently used systems are effective but exhibit high energy consumption. Resistive heating is used to prevent ice accretion or to release it once it has formed. To satisfy all the imposed airworthiness requirements, such as low aerodynamic impact, resistance to lightning strikes, no overheating, etc., multilayer systems are commonly configured with different layers fulfilling specific functions. For example, the Boeing 787 Dreamliner uses dry woven glass fiber fabric on top of the heating element to provide galvanic insulation and dielectric resistance. It satisfies the above-mentioned requirements, but its thermal conductivity is very low, therefore reducing energy efficiency. The thermal distribution of two materials (AA6061 aluminum alloy and PTFE) with significantly different thermal and electrical properties in contact with a heating element was studied. Finite element calculations and experimental testing in an icing wind tunnel were carried out at −12 °C under different convection conditions: natural (0 m/s) and forced (35 and 70 m/s), using specimens of different sizes. Heating elements areas were also varied. AA6061 showed homogeneous heating, whereas differences of up to 80 °C were observed when using PTFE. In addition, the test results highlighted the effect of forced convection and the need to evaluate these systems “in close to operative” conditions. The calculation results proved to it be an interesting tool for studying the behavior of the systems avoiding extensive testing.

전기펄스 제빙시스템의 전자기-구조변형-회로 결합 다물리 해석 기법

One of the ice protection systems for flights above medium altitudes is the electromagnetic explusive deicing system(EEDS). EEDS is composed of a coil which is structurally deformed by electromagnetic repulsion of electric current supplied by external circuit, a complex multiphysics phenomenon requiring electromagnetic, structural, and circuit analysis simultaneously. In this paper, we suggest electromagnetic(EM)-structural deformation-circuit coupled lumped parameter system for the analysis of EEDS. The results of the numerical analysis using the coupled lumped parameter system is compared with the results of measuring experiment using the EEDS prototype, which showed high concordance in current, electromagnetic force, and displacement. The coupled lumped parameter system enables bi-directional analysis which takes into account the interdependence between the different systems. Furthermore, it can significantly reduce the computational cost, which enables complex performance evaluation on various design variables and saves time and cost in the initial design steps.

Computational simulation of aircraft electrothermal de-icing using an unsteady formulation of phase change and runback water in a unified framework

Accurately predicting de-icing processes is essential to ensure the proper sizing and design of ice protection systems in aircraft icing. A unified framework was developed to simulate an unsteady electrothermal de-icing process, using an unsteady formulation to account for phase change and runback water. Two physically-motivated concepts were newly introduced to the icing model to accurately describe the unsteady electrothermal de-icing (ice accretion/melting) process. A conjugate heat transfer method was utilized to tightly couple the ice and conduction solvers. Sub-iterations were incorporated at every time step to ensure the convergence of temperature and heat flux at the interface. The unsteady de-icing framework consists of a compressible Navier-Stokes-Fourier airflow solver, Eulerian droplet impingement solver, unsteady ice accretion/melting solver, and heat conduction solver, which can handle multilayer composite materials. All solvers were formulated based on partial differential equations and developed in a unified finite volume framework, enabling the use of a single grid system and eliminating unnecessary grid generation for the ice layer. The results showed better agreement with experimental data compared to other results. The unified solver was used to analyze the unsteady electrothermal de-icing process by investigating the ice accretion, ice melting, runback water film, and freezing of water film in unprotected areas. Runback water film due to ice melting may exceed the impingement limits and freeze in unprotected areas, leading to ice ridge formation.

결빙이 중형 수송기의 공력에 미치는 영향성에 관한 전산 해석

When the aircraft flies through rain or clouds, supercooled water droplets or cloud particles cause aircraft icing by impinging on the surface of the aircraft. Accreted ice causes a change in the shape of the wing, negatively affects aerodynamic characteristics, and is a direct threat to safe flight. In this study, the effect of icing on the aerodynamic performance of medium-sized transport aircraft was analyzed by computational simulation. The iced area attached to the leading edge of the main wing and the tail wing was observed to be up to 5.3 cm. In addition, the reduction in aerodynamic performance was more considerable in the glaze ice condition due to the complicated geometry of ice. As a result of the study, the effect of icing on the lift and drag coefficient was investigated. The lift coefficient decreased by approximately 20% and the drag coefficient increased by approximately 70%. This suggests that icing will have a negative effect on the cruising range and endurance, which are important performances of medium-sized transport aircraft. In the future, this study can be extended to studies on the effects of ice accretion and design of ice protection systems.

Cohesive strength and fracture toughness of atmospheric ice

This paper aims at defining key mechanical properties of atmospheric ice in order to improve the design of mechanical de-icing systems. Based on ice fracture mechanisms, the parameters of interest are the cohesive strength of the ice and its fracture toughness. An hybrid experimental/numerical vibrating method is used to measure those critical values. Parameters such as temperature and precipitation rate influence the ice density and ice samples are thus defined with respect to this parameter. First the cohesive strength of ice is measured over the entire range of ice density and a polynomial expression of the cohesive strength of ice is given as a function of this density. Then the fracture toughness is measured for a smaller range of density and an average critical value is given. Finally, the influence of the properties computed are discussed to assess the conditions of atmospheric ice mechanical removal and the challenges for the design of mechanical ice protection systems. The study tends to show that as its density decreases, ice is more difficult to remove mechanically.

Improving mechanical ice protection systems with substrate shape optimization

Mechanical and electro-mechanical de-icing systems are low-energy ice protection solutions based on fracture mechanisms. It can, however, be difficult to obtain the protection of an entire surface due to the limited propagation of fractures for some mechanisms. This article shows how it is possible to reshape the substrate in order to favor the propagation of adhesive fracture at the ice/substrate interface. The first part of the paper introduces an analytical beam theory approach for running computations quickly, making it possible to achieve parametric optimization of the substrate thickness and maximize the propagation length. The optimization results were validated using FEM software and tests on an aluminum prototype. A second method is also studied in this paper, topology optimization is used on a 2D finite element model to minimize the substrate mass of the proposed solution and adhesive crack propagation is assessed in comparison with the mass impact. For different boundary conditions, propagation ranges can be increased by up to 150% with a mass increase limited to 50%. Using topology optimization, the additional mass could be reduced by >60% while maintaining the same performances.

Propeller-integrated airfoil heater system for small multirotor drones in icing environments: Anti-icing feasibility study

Atmospheric icing is one of the most common and hazardous environmental challenges for aircraft operations. So far, only large passenger aircraft, a few general aviation aircraft, and specialized rotorcraft are equipped with ice protection systems because of their additional energy consumption and weight. The emerging markets of small electric aircraft like Urban Air Mobility and Unmanned Aerial Vehicles for transportation, logistics, search and rescue, and other specialized operations will require efficient, lightweight and all-electric ice protection systems in order to allow operations in ice and snow conditions. In this work, an electrothermal ice protection system with an average heat power density of 1Wcm−2 was designed and developed for use on small multirotor drones. Commercially available propeller blades with diameters of 33cm were retrofitted with lightweight multilayer heating foils independently powered by super-capacitors. The heated propellers were tested in close-to-real icing conditions in a small-scale icing wind tunnel. Thrust, rotational speed, and power consumption of a non-heated reference propeller and a heated propeller were compared. In glaze ice conditions at air temperatures > −5°C the thrust of the non-heated propeller fluctuated between 60 and 90% with frequent cycles of ice accretion and shedding for the entire duration of the test. The heated propeller maintained a thrust of >95% in the same icing conditions. In rime ice conditions at air temperatures < −8°C the heating was not sufficient and the thrust of the non-heated and heated propellers similarly decreased over time. Heat flux calculations along the span of the propeller were made for different icing conditions and compared to the heat power density distribution of the tested ice protection system.

A Galerkin Method for the Simulation of Laminar Boundary Layers on Heated Walls

This paper presents a new solution method for the calculation of laminar thermal boundary layers. The method consists of a coupling between a modal method (Galerkin method) in the direction normal to the wall and a finite volume method in the direction(s) tangential to the wall. It is similar to an integral method in the sense that only a surface mesh is required and that the unknowns are integral quantities (corresponding to the moments up to a fixed order of the temperature profile in the direction normal to the wall). A specificity of the Galerkin method used is that the domain over which the integrals are computed has a variable size that is also an unknown of the problem. Using a series of numerical tests (representative of situations that can be encountered in aeronautics in the case of a wing equipped with a thermal ice protection system), we show that the new method allows us to predict the quantities of interest with a maximum error of a few percent, while a usual integral method (with only one unknown per mesh cell) is unable to treat the case of boundary layers on heated walls with a strong longitudinal temperature gradient, as shown in the literature.

Ice accretion and aerodynamic effects on a turbofan engine nacelle under takeoff conditions

A complete three-dimensional icing prediction method is established, including airflow calculation, droplet impingement calculation, 3-D ice accretion calculation, and grid regeneration. The 3-D ice accretion solver considers the effect of unfrozen liquid water by supplementing a runback water model. After verifying the 3-D icing prediction method with experimental results, the ice accretions and their aerodynamic effects on a nacelle for an aircraft bypass turbofan engine are investigated during the takeoff and initial climb phases. At the end of the Takeoff phase, the drag is almost unchanged, and the lift capability even shows a slight increase. There is no threat to the aerodynamic performance of the nacelle when the ice protection system is not active under the prescribed icing conditions. The aerodynamic performance gradually worsens as ice accretes in the subsequent phases. And the aerodynamic performance is more susceptible for the iced nacelle than the clean one under takeoff conditions.

Improving mechanical ice protection systems with topology optimization

In the context of more electrical aircraft, electromechanical de-icing systems provide a low-energy solution to protect aircraft’s surfaces from ice buildup. Such systems produce deformation of the protected surface leading to a stress production within the ice and, ultimately, to ice shedding thanks to fracture. However, these systems may show limitations when it comes to completely protect a given surface. Ice delamination is often restricted to a part of the surface and the remaining ice either requires more energy to be removed or is just impossible to remove. In this paper, topology optimization of the substrate covered by ice is thus investigated to increase fracture propagation and ice shedding. For that purpose, an optimization problem, involving the energy release rate but also the mass and the substrate stress, is formulated. The numerical results show how the delamination efficiency of mechanical based ice protection systems can be improved through the topology modification of the substrate.

Design of the Thermoelectric Ice Protection System for a Tiltrotor Application

This work presents the methodology and the results of the numerical design of a thermoelectric ice protection system (IPS) for the rotor blade of the Leonardo Next Generation Civil Tiltrotor. The IPS architecture is made up of two systems: a primary and a secondary one (backup). The primary IPS consists of a parting strip in the outer half of the blade, extending from 3% of the chord on the suction side to 4% on the pressure side, coupled with eight de-icing zones extended chordwise until 24.5% on the pressure side, and from 14.5 to 24.5% on the suction side (depending on the zone). The secondary IPS consists of the same parting strip configuration, coupled with a reduced system for the de-icing zones made of four regions, chordwise extended till 10% on the pressure side, and till 13% on the suction side. The parting strip is sized according to the end-user’s geometrical and power constraints, whereas the de-icing zones are sized for achieving the required effective heat flux and operated according to a cyclic timing law. The composite blade is also checked for its capability to sustain the thermal stress from the operation of the IPS.

Characterization in Relevant Icing Conditions of Two Superhydrophobic Coatings

The formation of ice can be very detrimental to flight safety, since the ice accumulated on the surfaces of the aircraft can alter both the aerodynamics and the weight, leading in some cases to catastrophic stall situations. To date, only active Ice Protection Systems (IPS), which require energy to work, are being employed. The use of passive coatings able to prevent, delay, or reduce ice accretion in real flight icing conditions can be viewed as a valuable instrument to reduce the environmental footprint of aircraft. The majority of work in the literature focuses on testing superhydrophobic coatings at a speed equal to or lower than 50 m/s or rather in combination with an active system. The present study was aimed at understanding the effectiveness of two superhydrophobic coatings applied on two NACA0015 wing profiles in reducing the ice formation in relevant flight icing conditions, through tests carried out in an Icing Wind Tunnel at 50 and 95 m/s and at temperatures ranging between −3 and −23 °C. Results demonstrated that at temperatures higher than −12 °C, at both 50 and 95 m/s, with exposure time ranging between 72 and 137 s, the developed coatings can be helpful in reducing the ice accretion by 12 to 100%.

Ultrasonic inspection for ice accretion assessment: effects on direct wave propagation in composite media

From aeroplane wings to overhead power lines, through giant blades of wind turbines, a build up of ice can cause problems ranging from impaired performance all the way to catastrophic failure. Therefore, it is of the utmost importance to control or prevent ice formation, especially on the critical areas of a structure. However, de-icing and anti-icing countermeasures can result energetically expensive and hazardous to the environment. In addition, excessive use of such of them will reduce the life of the ice protection system and introduce fatigue to the controlled structures. Thus, in order to manage properly the available resources, it is desirable to have an ice detection system that can both detect ice formation and monitor the thickness of ice on critical surfaces. This would allow acting when it is necessary. Ultrasonic guided-wave-based technique has been proved reliable for ice detection, but approaches to establish ice accretion over time have not been provided yet. The paper investigates the interaction of ultrasonic direct waves in composite plate with ice layers and the effects of ice thickening on the ultrasound propagation. Moreover, the use of metrics is discussed as indicators of ice growth.

Numerical Simulation of Aircraft Icing under Local Thermal Protection State

The icing phenomenon seriously threatens flight safety, and, therefore, the aircraft needs to be equipped with an icing protection system. Icing may still occur when the anti-icing system is in operation when the protection range or protection power is too small. Given this state, the ice shapes of the airfoil under local thermal protection states are studied in this paper. A numerical simulation method for icing considering water film flow is demonstrated. The solution methods for the governing equations and convective heat transfer coefficient are given. The calculation results were compared with experimental data and a LEWICE calculation to verify the validity of the method. Different protection ranges and protection powers were designed, and the ice shapes under different conditions were simulated. The calculation results show that when the protection range is large, but the protection power is low, icing will still occur in the protection range. Alternatively, when the protection range is small, icing may form outside the protection area. When the combination of protection range and protection power is inappropriate, the critical ice ridge phenomenon will occur. Ice ridges cause the degradation of aerodynamic characteristics and are more dangerous than icing.

A Review on the Estimation of Power Loss Due to Icing in Wind Turbines

The objective of this article is to review the methodologies used in the last 15 years to estimate the power loss in wind turbines due to their exposure to adverse meteorological conditions. Among the methods, the use of computational fluid dynamics (CFD) for the three-dimensional numerical simulation of wind turbines is highlighted, as well as the use of two-dimensional CFD simulation in conjunction with the blade element momentum theory (BEM). In addition, a brief review of other methodologies such as image analysis, deep learning, and forecasting models is also presented. This review constitutes a baseline for new investigations of the icing effects on wind turbines’ power outputs. Furthermore, it contributes to a continuous improvement in power-loss prediction and the better response of icing protection systems.

Towards standards in the analysis of wind turbines operating in cold climate. Part B: Methodology for evaluating wind turbine alternative operational strategies

Alternative operational strategies are now being used to cope with the challenges of icing on wind turbines. However, there are currently no generally accepted standards for the performance analysis of wind turbines using such alternative operational strategies. Hence, this is an important research topic that needs to be addressed. The aforementioned alternative operational strategies include ice protection systems (installation or modification) and alternative turbine control strategies. The interest surrounding the performance analysis of such strategies is rising since, as the demand for ice protection systems from wind turbine original equipment manufacturer and retrofits providers is increasing worldwide, operators are requesting warranties surrounding their performance. Due to their novelty, operators often prefer to test alternative operational strategies on a few turbines before deploying them on every turbines of a wind farm. In those situations, a standard and robust method is needed to evaluate the strategy before a full-scale extension. This paper proposes a methodology based on the experience gathered on five undisclosed wind farms where different operational strategies were implanted. Through case studies, the current metrics used to assess the performance of alternative operational strategies are reviewed and two new metrics that address the main issues with the current indicators are proposed. These new metrics can estimate the energy reclaimed through the use of alternative operational strategies. This paper also presents a methodology for selecting the best turbines that will be used as a reference to evaluate the performance of the turbines with the alternative operational strategies. Standardized metrics with the right turbines used as a reference will help to provide a clearer overview of the performance of wind turbines in icing conditions. Furthermore, it will help to reduce the uncertainties on the gains achieved through alternative operational strategies. The proposed methodology can be used by operators to compute the payback and quantify the added value of such modifications on their wind farm. It also helps to understand when a strategy is efficient, therefore helping to improve the development of new alternative operational strategies. Finally, using this methodology, through a case study, we demonstrated that the three control turbines could have recovered between 54 and 56% of their icing losses if they were equipped with a Borealis Wind Ice Protection System (IPS).

Anti-Icing Engine Damage Analysis Boeing 737 - 800 Ng With Fault Tree Analysis Method

An Anti-icing system is a system that aims to prevent the formation of ice when the plane is in the air. The formation of ice in aircraft is of great concern because an airplane flight will pass through the atmosphere, which will experience the formation of the ice at a certain altitude. The formation of such ice will cause a hazard to the aircraft. So that the ice protection system, namely the anti-icing system, is very concerned so that it is always in a serviceable condition. In this study, direct observation and fault tree analysis were used to determine the cause of failure of the Boeing 737-800 NG anti-ice system engine and anti-icing cowl inlet. The results of the analysis using the fault tree analysis method obtained essential events, namely: actuator fails, electrical connector disconnected, Control Selenoid Trouble, Regulator Trouble, Sense Line Connector Trouble, Engine Fault, Engine Control Trouble, Engine Duct Trouble, Panel Buttom Problem, EICAS Module Problem, No Source Electricity, Negative Electrical Source, Wiring Problem.

Anti-Icing Engine Damage Analysis Boeing 737 - 800 Ng With Fault Tree Analysis Method

An Anti-icing system is a system that aims to prevent the formation of ice when the plane is in the air. The formation of ice in aircraft is of great concern because an airplane flight will pass through the atmosphere, which will experience the formation of the ice at a certain altitude. The formation of such ice will cause a hazard to the aircraft. So that the ice protection system, namely the anti-icing system, is very concerned so that it is always in a serviceable condition. In this study, direct observation and fault tree analysis were used to determine the cause of failure of the Boeing 737-800 NG anti-ice system engine and anti-icing cowl inlet. The results of the analysis using the fault tree analysis method obtained essential events, namely: actuator fails, electrical connector disconnected, Control Selenoid Trouble, Regulator Trouble, Sense Line Connector Trouble, Engine Fault, Engine Control Trouble, Engine Duct Trouble, Panel Buttom Problem, EICAS Module Problem, No Source Electricity, Negative Electrical Source, Wiring Problem.

On a reduced-order model-based optimization of rotor electro-thermal anti-icing systems

PurposeResponsible for lift generation, the helicopter rotor is an essential component to protect against ice accretion. As rotorcraft present a smaller wing cross-section and a lower available onboard power compared to aircraft, electro-thermal heating pads are favored as they conform to the blades’ slender profile and limited volume. Their optimization is carried out here taking into account, for the first time, the highly three-dimensional (3D) nature of the flow and ice accretion, in contrast to the current state-of-the-art that is limited to two-dimensional (2D) airfoils.Design/methodology/approachConjugate heat transfer simulation results are provided by the truly 3D finite element Navier–Stokes analysis package-ICE code, embedded in a proprietary rotorcraft simulation toolkit, with reduced-order modeling providing a time-efficient evaluation of the objective and constraint functions at every iteration. The proposed methodology optimizes heating pads extent and power usage and is versatile enough to address in a computationally efficient manner a wide variety of optimization formulations.FindingsLow-error reduced-order modeling strategies are introduced to make the tackling of complex 3D geometries feasible in todays’ computers, with the developed framework applied to four problem formulations, demonstrating marked reductions to power consumption along with improved aerodynamics.Originality/valueThe present paper proposes a 3D framework for the optimization of electro-thermal rotorcraft ice protection systems, in hover and forward flight. The current state-of-the-art is limited to 2D airfoils.

Improving Mechanical Ice Protection Systems with Substrate Parametric and Topology Optimization

Improving Mechanical Ice Protection Systems with Substrate Parametric and Topology Optimization