Electrothermal Ice Protection System Research Articles

Design and optimization of a modular Electro-Thermal Ice Protection System for a Horizontal Axis Wind Turbine

In this work, an Electro-Thermal Ice Protection System (IPS) design was refined and optimized on the NREL 5 MW reference wind turbine. These improvements involved optimization of the distribution of heat flux in both the stream-wise and span-wise directions to minimize power consumption and avoid run-back ice formation. The design conditions focus on a 3-hour rime ice accretion event. The chosen optimization algorithm is a derivative-free method called Mesh Adaptive Direct Search. his optimization effort results in a 55% reduction in power consumption necessary to maintain a completely clean blade surface. The power and energy losses associated with this new optimized design are compared with those from various ice shapes and with the clean blade conditions established in the initial design phase from previous work. The new optimized design allows to keep the blade clean from ice with much larger energy saving. Indeed, only initially, during the first two hours of ice accretion, the energy losses due to this IPS design are higher than without IPS. Beyond this short initial period, substantial energy savings are achieved, especially considering that after the accretion event, the blade remains ice-free, and there are no more power losses.

In-flight anti-icing simulation of electrothermal ice protection systems with inhomogeneous thermal boundary condition

Conventional anti-icing computational solvers calculate the convective heat transfer coefficient using a homogeneous thermal boundary condition, assuming a constant temperature across the surface. However, this approach can lead to inaccuracies in regions with significant temperature variations. To address this limitation, the present study proposes a novel approach that utilizes an inhomogeneous thermal boundary condition, which updates the convective heat transfer coefficient based on the transient wall temperature distribution. We developed a unified finite volume framework that efficiently integrates various in-house solvers, including a compressible Navier-Stokes-Fourier (NSF) airflow solver, a Eulerian droplet impingement solver, a PDE-based ice solver, and a multilayer heat conduction solver. Thermal interaction between the different solvers was modeled using the conjugate heat transfer method. The effects of updating airflow on anti-icing results were investigated by comparing the results obtained by coupled and decoupled solvers. While the decoupled solver computes airflow once and remains unchanged, the coupled solver updates the airflow during the anti-icing simulation. Our findings show that the decoupled solver has the highest deviations from the coupled solver in evaporative anti-icing regimes, where dry regions form within the protection limits. Using coupled solvers in designing ice protection systems in evaporative regimes improves temperature prediction accuracy, enabling designers to reduce safety factors and save energy.

Ice shedding tests for the assessment of hybrid ice protection systems

In technical areas, the prevention of atmospheric icing on structures is imperative due to safety risks and potential technical failures it poses. Recent development projects have focused on hybrid ice protection systems, combining active elements (heaters/mechanical actuators) with passive icephobic coatings. However, there is a lack of test strategies for the early development stages of these coating materials. An efficient test design for an ice wind tunnel is described here, developed to quantitatively assess the ice shedding effects facilitated by icephobic surfaces in electro-thermal ice protection systems. Dependencies on test and surface parameters are explored, laying the groundwork for defining test procedures for subsequent surface evaluations. During testing, utilizing a hydrophobic model coating, a reduction in energy of over 30% was observed compared to uncoated aluminium. This finding highlights the potential effectiveness of icephobic surfaces in mitigating icing effects. The presented test serves as a valuable tool for pre-selecting the most promising surfaces for further advanced tests, particularly those involving aerodynamic profiles within the ice wind tunnel test facility. It constitutes a vital component of a comprehensive test pyramid, encompassing ice-related tests with increasing complexity. Furthermore, the results obtained from these tests are utilised to establish correlations with surface properties, thereby enhancing our understanding of the significance of these findings. This approach provides a well-founded testing strategy for evaluating and advancing icephobic surface technologies.

Integrated composite electrothermal de-icing system based on ultra-thin flexible heating film

Icing is a serious threat to the flight safety of aircraft. Lightweight and efficient electrothermal de-icing systems for carbon fiber reinforced polymer components are expected to contribute to the lightweighting and electrification of aircraft. This study presents the development and test of a novel, integrated, multifunctional composite electrothermal ice protection system. The system achieves this by incorporating a carbon-based ultra-thin flexible heating film into a carbon fiber-reinforced polymer composite laminate. T700 and M40 carbon fiber prepregs were used. The system composition and configuration were designed based on the anisotropic mechanical and thermal properties of the carbon fiber-reinforced polymer composite. The effects of ply stacking sequence, presence of insulation layer, ply angle, heating area, and prepreg type on thermal response and de-icing performance were investigated. Thermal response experiments were carried out in both room temperature and low temperature environments. A one-dimensional thermal response analysis model was developed for a representative heating structure. Comparative de-icing experiments were conducted on different samples in a low-temperature test chamber. A numerical model, based on the modified enthalpy-porosity method, was developed to simulate the de-icing process, and showed good agreement with the experimental results. Experiments and numerical calculations show that the arrangement of the heater close to the deicing surface improves the performance of the electrothermal deicing system while maintaining the overall mechanical properties of the multi-layer structure. While the insulation layer helps marginally with heat loss during de-icing, it significantly increases the system’s thermal inertia, which delays the de-icing’s start. It is recommended to minimize or eliminate insulation layer thickness. Rapid de-icing effects, combined with energy conservation, can be achieved through a short-term, high-power heating strategy.

UAV icing: Development of an ice protection system for the propeller of a small UAV

Atmospheric icing, also called in-flight icing, is a common hazard for the operation of uncrewed aerial vehicles (UAVs). With the background of a growing commercial and military market of small and medium-sized drones and the developments in the urban air mobility markets, protecting the propellers of UAVs against icing has become a pivotal technology to unlock the potential of these markets. The propellers and rotors accumulate ice faster than the UAVs’ wings and airframe. This ice accumulation leads to aerodynamic degradation, making the protection of the propeller key for the operation of UAVs in conditions with potential icing. In this work, an electro-thermal ice protection system is developed for a propeller of a small UAV, with a propeller diameter of 53 cm or 21 inch. For the design of the system, the required anti-icing heat fluxes were calculated using icing computational fluid dynamics (CFD) analysis. Carbon fibre-based heating elements were integrated into the structure of the propeller. This propeller was tested in an icing wind tunnel at −5 °C, −10 °C, and −15 °C. The tests were performed with a rotation rate representative for a medium-sized UAV of 4200 rpm. The liquid water content of the wind tunnel was 0.44 g/m3. It prevented the performance penalties from ice accretion at temperatures of −5 °C. At lower temperatures, the propeller IPS could limit the ice accretion on the propeller, thus allowing it to retain its ability to create thrust. The results showed a requirement for a significantly higher heat flux than predicted by the CFD analysis. This work is the first step in developing a mature ice protection system for the propellers and rotors of medium-sized UAVs and to enable all-weather operations.

Robust Optimization of a Thermal Anti-Ice Protection System in Uncertain Cloud Conditions

This paper presents a framework for the robust optimization of the heat flux distribution for an anti-ice electrothermal ice protection system under uncertain conditions. The considered uncertainty regards a lack of knowledge concerning the characteristics of the cloud, i.e., the liquid water content and the median volume diameter of water droplets, and the accuracy of measuring devices, i.e., the static temperature probe. Uncertain parameters are modeled as random variables, and two sets of bounds are investigated. A forward uncertainty propagation analysis is carried out using a Monte Carlo approach exploiting a surrogate models. The optimization framework relies on a gradient-free algorithm (mesh adaptive direct search), and two different objective functions are considered, namely, the 95 quantile of the freezing mass rate and the statistical frequency of the fully evaporative operating regime. The framework is applied to a reference test case, revealing a potential to improve the heat flux distribution of the baseline design. A new heat flux distribution is proposed, and it presents a more efficient use of the thermal power, increasing flight safety even at nonnominal environmental conditions.

Electrothermal Ice Protection Systems De-Icing: An Experimentally Validated Idealized Ice Shedding Model

The increased use of electrothermal ice protection systems (ETIPSs) in various industries (manned and unmanned aviation, energy production) requires improvements to de-icing efficiency, ice shedding predictability, and energy consumption. To achieve these, a coupled numerical and experimental investigation of ETIPS’s ice removal (ice shedding) mechanism is presented in this paper. Idealized ETIPS de-icing experiments performed in the icing wind tunnel of the von Karman Institute show several ice shedding mechanisms. A one-dimensional phase change solver developed for ice melting simulations highlights the water layer thickness influence over the ice shedding process. Coupled numerical–experimental results are employed to develop an idealized ice shedding model. The model is validated in realistic de-icing experiments in a second experimental campaign in the icing wind tunnel of the LeClerc Icing Research Laboratory.

Optimisation of a Nacelle Electro-Thermal Ice Protection System for Icing Wind Tunnel Testing

Abstract Aircraft are equipped with ice protection systems (IPS), to avoid, delay or remove ice accretion. Two widely used technologies are the thermo-pneumatic IPS and the electro-thermal IPS (ETIPS). Thermo-pneumatic IPS requires air extraction from the engine negatively affecting its performances. Moreover, in the context of green aviation, aircraft manufacturers are moving towards hybrid or fully electric aircraft requiring all electric on-board systems. In this work, an ETIPS has been designed and optimised to replace the nacelle pneumatic-thermal system. The aim is to minimise the power consumption while assuring limited or null ice formation and that the surface temperature remains between acceptable bounds to avoid material degradation. The design parameters were the length and heat flux of each heater. Runback ice formations and surface temperature were assessed by means of the in-house developed PoliMIce framework. The optimisation was performed using a genetic algorithm, and the constraints were handled through a linear penalty method. The optimal configuration required 33% less power with respect to the previously installed thermo-pneumatic IPS. Furthermore, engine performance is not affected in the case of the ETIPS. This energy saving resulted in an estimated reduction of specific fuel consumption of 3%, when operating the IPS in anti-icing mode.

Numerical Simulation of an Electrothermal Ice Protection System in Anti-Icing and Deicing Mode

The design of efficient thermal ice protection systems is a challenging task as these systems operate in complex environments involving several coupled physical phenomena such as phase change, boundary-layer flow, and heat transfer. Moreover, certification rules are becoming more stringent, and there is a strong incentive for the reduction of fuel consumption. In this context, numerical tools provide a powerful asset during the design phase but also to gain insight into the physical mechanisms at play. This article presents modeling and simulation strategies for thermal ice protection systems. First, the model describing the behavior of the thermal protection system is presented. Second, a model and associated numerical method is presented for unsteady ice accretion. Third, the coupling methodology between the ice accretion solver and the heat conduction solver is described. In the fourth part, different methods to simulate the boundary-layer flow are described. Finally, some relevant examples are presented, both in steady and unsteady configurations.

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.

Multiphysics anti-icing simulation of a CFRP composite wing structure embedded with thin etched-foil electrothermal heating films in glaze ice conditions

Electrothermal ice protection systems (IPS) for CFRP composite aircraft face distinct challenges because of the composite structure’s relatively low thermal conductivity and vulnerability to overheating. In this work, the thermal response of a thin etched-foil heating film-based IPS integrated into CFRP laminates was characterized both experimentally and by thermal FEM simulation. A resulting IPS configuration was implemented in a CFRP wing skin laminate model of an unmanned aerial vehicle (UAV) for multiphysics icing simulation. Glaze ice accretion and melting were simulated with in-flight conditions and varying heater heat fluxes and angles of attack. Sharp surface temperature drops were observed in the heating film gap regions, which led to the implementation of a quasi-continuous film spacing. A uniform heater heat flux of 7.5 kW/m2 achieved anti-icing functionality with an associated surface temperature range of 0–13 °C. This range revealed the merit of heat flux zone modulation to uniformly distribute the surface temperature and improve the overall energy efficiency of the system.

Experimental and numerical analysis of anti-icing a GLARE laminate

Abstract This study aimed at developing a numerical model to estimate the power consumption of a GLAss fiber REinforced aluminum-based electro-thermal ice protection system for anti-icing. The GLAss fiber REinforced aluminum laminate was embedded with recurred S-shaped copper meshes thermally energized by a surface power density. The model determined the influence of a forced convective heat loss and copper-mesh dimension on anti-icing. As a test case, the numerical model addressed the anti-icing performance of a GLAss fiber REinforced aluminum 5A-3/2 laminate at a sub-freezing ambient temperature of 267.95 K. The model demanded a surface power density of 13.03 kW/m2 in order to keep the temperature of the outer aluminum-skin at 285.44 K, which was clearly beyond the water freezing point. The numerically predicted power consumption for anti-icing was in excellent agreement with that from the experiment. The experiment was conducted in a miniature icing wind tunnel by incorporating the comparable icing condition of the numerical analysis. In the experiment, an infrared thermography camera determined the spatio-temporal temperature history of the outer aluminum skin in contact with the free-stream. The infrared thermography camera measurements of surface temperature collapsed in close proximity to that from the numerical analysis. The outcomes of this study will consolidate the confidence of aircraft manufacturers on the proposed anti-icing system.

Experimental Heat Loads for Electrothermal Anti-Icing and De-Icing on UAVs

Atmospheric in-flight icing on unmanned aerial vehicles (UAVs) is a significant hazard. UAVs that are not equipped with ice protection systems are usually limited to operations within visual line of sight or to weather conditions without icing risk. As many military and commercial UAV missions require flights beyond visual line of sight and into adverse weather conditions, energy-efficient ice protection systems are required. In this experimental study, two electro-thermal ice protection systems for fixed-wing UAVs were tested. One system was operated in anti-icing and de-icing mode, and the other system was designed as a parting strip de-icing system. Experiments were conducted in an icing wind tunnel facility for varying icing conditions at low Reynolds numbers. A parametric study over the ice shedding time was used to identify the most energy-efficient operation mode. The results showed that longer intercycle durations led to higher efficiencies and that de-icing with a parting strip was superior compared to anti-icing and de-icing without a parting strip. These findings are relevant for the development of energy-efficient systems in the future.

Numerical simulation of a thermal Ice Protection System including state-of-the-art liquid film model

In this work, a numerical model for the operation of an electro-thermal Ice Protection Systems (IPS) for an airfoil is presented. The present model solves the energy conservation laws and includes a boundary layer model to compute the relevant aerodynamic quantities based on previous works. Additionally, the computation of aerodynamic and water impingement properties is performed by means of open-source and in-house developed software. A state-of-the-art liquid film model based on lubrication theory has been deployed as an alternative to an element-wise mass balance. A simple ice formulation for the prediction of the formation of runback ice has been included. Moreover, a robust evaporation model based on the heat and mass transfer analogy is deployed. Finally, an interpolation scheme for the element-wise enthalpy variation is presented. The results obtained are in good agreement with the experimental data from the open literature for a range of different test cases including different operating modes, environmental and flight conditions.

Deicing of a GLAss fiber REinforced aluminum laminate – Part 1: Experiments and numerical simulation

Deicing is a mandatory procedureto ensure the required aerodynamic lift of aircraft. Countless experimental and numerical investigations have been conducted to determine the deicing efficiency of various ice protection systems. The literature review, however, yielded no single study that has been dedicated to investigate the deicing performance of a GLAss fiber REinforced aluminum (GLARE)-based electro-thermal ice protection system. Of notes, the upper fuselage of the front- and the rear section of Airbus A380 comprises circa 469 m2 of GLARE. This study, therefore, proposed a phase change model based on thermo-dynamics to determine the power consumption and the de-icing performance of a GLARE laminate embedded with recurring S-shaped copper heater elements. The model addressed the influence of copper mesh length and orthotropic properties of GLARE on deicing.As a test case, the power budget for deicing a GLARE 5A-3/2 laminate was predicted numerically. The numerical analysis demonstrated that a surface power density of 14.62 kW/m2 sufficed to deice a GLARE 5A-3/2 laminate covered with a 0.8 mm thick ice layer at an ambient temperature of 267.15 K. To corroborate the numerical predictions, deicing experiments had been conducted in a miniature icing wind tunnel by incorporating icing conditions comparable to that of the numerical analysis. It was found that the predicted surface power density was in excellent agreement with that determined in the deicing experiment. In the experiment, an infrared camera measured the temperature gradient of the GLARE specimen, which was also in close proximity to that of the GLARE model in the numerical analysis.

Numerical Optimisation of a Helicopter Engine Inlet Electrothermal Ice Protection System

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This paper details the process involved in the numerical optimisation of a helicopter engine inlet electrothermal ice protection system. Although the process was developed using a production aircraft, it is demonstrated here using a generic intake and flight conditions, due to confidentiality of the actual design. The process includes adherence to the overall system design objectives (maximum power demand), including tolerances required to account for an industrial system (aircraft voltage variation, manufacturing tolerances). The numerical optimisation was performed using a combination of 2D and 3D methods to define the required heated area, power density, locations and settings for temperature control sensors. The use of 2D design tools allows a rapid iteration process to be performed, leading to the possibility of a higher level of optimisation within the allowable time-frame compared to the use of full 3D methods. Different flight settings (different Angle of Attack and Angle of Sideslip) were analysed, for two different droplet diameters (MVD values of 20 microns and 40 microns, coherent with the requirements of the CS-29 Appendix C icing envelope). An iterative transient thermal analysis was then performed, over the required temperature range of 0°C to -30°C, to optimise the heater placement and heater powers, assessing the predicted level of ice accretion in all cases. Assessment in dry conditions in the range of +5°C to -30°C was also performed in order to ensure that structural over-temperature did not occur. The positions of embedded temperature sensors were defined as part of the analysis, including the temperature control values which would feed into the controller. The process was deemed to be successful as the final design was successfully tested in flight and in an icing wind tunnel facility.&lt;/div&gt;&lt;/div&gt;

A Study on Aircraft Anti-icing Systems

Aircraft anti-icing system is one of the key components without which aircraft icing related problems cannot be solved. Considering the long history of aircraft building technologies the involvement of anti-icing system has a remarkable influence over it. Basically there exist two types of aircraft anti-icing systems namely, the first one is electro-thermal anti-icing system the second one is bleed air anti-icing system. For propellers electro-thermal anti-icing system is used and for fixed wing planes the bleed air anti-icing system is used to prevent icing on the wings. Apart from these two anti-icing systems there exist several other anti-icing systems for the prevention of ice formation. It should be noted that anti-icing and de-icing are two different systems with different purposes. A short study of different aircraft anti-icing systems has been carried out for better understanding. The paper shows various aspects and methods of anti-icing systems used. Keywords: Aircraft Anti-Icing, bay model, de-icing, bleed air, electro-thermal ice protection system, electro-expulsive separation system, ultrasound actuator Cite this Article Bhavik D. Lathigara, Vinal G. Virani. A Study on Aircraft Anti-icing Systems. Journal of Aerospace Engineering and Technology. 2016; 6(2): 9–15p.

Transient simulation and analysis of wing electrothermal ice protection system

The transient behaviour of electric heating and de-icing of the wing is studied by numerical method. The thermal convection coupling method based on the equivalent heat transfer coefficient and the boundary condition iteration is developed for the two designed schemes of the electric heating system. According to the surface temperature, the internal temperature, and the icing condition, the system transient performance is investigated. The purpose of this study is to establish the de-icing transient model of the wing ice protection system, simulate the transient de-icing process and form the method of performance estimation. The results under different working conditions show that the temperature distribution of the skin surface is not uniform, rather presents certain regularity. The rising rate of temperature decreases with the increase of the temperature. The trend is more obvious at lower ambient temperature, when the ambient temperature rises, the surface temperature rises rapidly in a short period. Scheme 2 has certain advantages in heating capability, while the hot knives structure of scheme 1 can narrow and split the icing area.

Aero-thermal optimization of in-flight electro-thermal ice protection systems in transient de-icing mode

Even if electro-thermal ice protection systems (IPS) consume less energy when operating in de-icing mode than in anti-icing mode, they still need to be optimized for energy usage. The optimization, however, should also take into account the effect of the de-icing system on the aerodynamic performance. The present work offers an optimization framework in which both thermal and aerodynamic viewpoints are taken into account in formulating various objective and constraint functions by considering the energy consumption, the thickness, the volume, the shape and the location of the accreted ice on the surface as the key parameters affecting the energy usage and the aerodynamic performance. The design variables include the power density and the activation time of the electric heating blankets. A derivative-free technique, called the mesh adaptive direct search (MADS) method, is used to carry out the optimization process, which would normally need a large number of unsteady conjugate heat transfer (CHT) calculations for the IPS simulation. To avoid such prohibitive computations, reduced-order modeling (ROM) is used to construct simplified low-dimensional CHT models. The approach is illustrated through several test cases, in which different combinations of objective and constraint functions, design variables and cycling sequence patterns are examined. In these test cases, the energy consumption is significantly reduced compared to the experiments by improving the spatial and temporal distribution of the thermal energy usage. The results show the benefits of the approach in bringing energy, safety and aerodynamic considerations together in designing de-icing systems.

Numerical simulation and modeling of ice shedding: Process initiation

In aeronautics, the issue of ice shedding prediction is of prime importance in the assessment of electro-thermal ice protection systems. In this paper, an ice shedding mechanism based on pressure redistribution in the water film formed at the ice/airfoil interface is proposed. This pressure distribution induces a stress concentration that leads to crack propagation in the ice. To determine whether this mechanism is relevant or not, two numerical experiments are performed. The results of these numerical experiments and the influence of a few material parameters are discussed, as well as their limitations and possible consequences arising from some of the hypotheses.The numerical modeling is based on recent works on damage/fracture mechanics which provide a general framework for fracture mechanics computation. The effects of numerical parameters and mesh size are discussed. A mixed mode test case based on experimental data is also performed. This test case had not been attempted before on this particular numerical method, which therefore serves as further validation.