Hot Air Anti-icing System Research Articles

Prediction of Temperature Distribution on an Aircraft Hot-Air Anti-Icing Surface by ROM and Neural Networks

To address the inefficiencies and time-consuming nature of traditional hot-air anti-icing system designs, reduced-order models (ROMs) and machine learning techniques are introduced to predict anti-icing surface temperature distributions. Two models, AlexNet combined with Proper Orthogonal Decomposition (POD-AlexNet) and multi-CNNs with GRU (MCG), are proposed by comparing several classic neural networks. Design variables of the hot-air anti-icing cavity are used as inputs of the two models, and the corresponding surface temperature distribution data serve as outputs, and then the performance of these models is evaluated on the test set. The POD-AlexNet model achieves a mean prediction accuracy of over 95%, while the MCG model reaches 96.97%. Furthermore, the proposed model demonstrates a prediction time of no more than 5.5 ms for individual temperature samples. The proposed models not only provide faster predictions of anti-icing surface temperature distributions than traditional numerical simulation methods but also ensure acceptable accuracy, which supports the design of aircraft hot-air anti-icing systems based on optimization methods such as genetic algorithms.

Experimental and numerical investigations on jet impingement heat transfer with different nozzles and enhanced surfaces

Hot air anti-icing systems are essential in aviation engines, preventing ice formation on inlet components during high-altitude flights. A critical factor in enhancing these systems' effectiveness is the application of jet impingement technology. In order to further enhance the performance of jet impingement heat transfer in this application scenario, the research assesses the impact of nozzle type and surface protrusion type on the anti-icing system's performance by integrating experimental and numerical approaches. Findings reveal that circular nozzles outperform swirl and satellite nozzles in heat transfer efficiency in the application of aviation anti-icing system with high jet Reynolds number. The average Nusselt number, indicative of heat transfer rate, can be increased by up to 10.54 % with protrusions. For surface protrusions, sequentially-arranged cylinder protrusions are more effective at Reynolds numbers between 8000 and 48000. Cross-arranged circular truncated cone protrusions do better at higher Reynolds numbers, from 48000 to 80000 which is the range relevant to the hot air anti-icing system. Comparing concave and flat plates with the same type of protrusions, the former shows superior heat transfer performance. The study also establishes correlations for convective heat transfer coefficients and attenuation coefficients on the concave plate with sequentially-arranged cylinder protrusions. By applying the cross-arranged circular truncated cone protrusions, which proved to be the best in our experiments, to the engine nacelle's anti-icing section, the numerical results indicate a 6.21 % increase in anti-icing thermal efficiency and an 8.31 % decrease in air bleed capacity, all under the same heat transfer conditions. The use of protrusion structures in the anti-icing system of an engine nacelle boosts thermal efficiency, lowers air bleed capacity, and reduces the fuel penalty, thereby optimizing overall performance.

Experimental validation and tightly coupled numerical simulation of hot air anti-icing system based on an extended mass and heat transfer model

When an aircraft flies through a cloud containing supercooled liquid water droplets, ice accretion may deposit, posing a threat to flight safety. Hot air anti-icing is one of the most widely used anti-icing techniques. An extended mass and heat transfer model for runback water on a hot air anti-icing surface is developed. The model is based on the mass conservation and energy conservation of continuous water film and rivulet water film, considering the conditions under which continuous water film may break up into rivulet water film. Additionally, the effect of water vapor resulting from liquid water evaporation is also taken into account. Then, a three-dimensional tightly coupled numerical method for hot air anti-icing systems is constructed based on the developed model. The method includes modules for the calculation of external cold air flow, solid skin heat conduction and internal hot air flow, the calculation of water droplet impingement, and the calculation of anti-icing thermodynamics. The accuracy of the method is validated against experimental studies on an enhanced heat transfer piccolo tube anti-icing system in the icing wind tunnel of China Aerodynamics Research and Development Center (CARDC). The temperature results obtained from the three-dimensional numerical simulations showed good agreement with the experimental results, indicating that this method can be utilized in preliminary and detailed designs to evaluate the thermal performance of hot air anti-icing systems.

Single- and multi-objective optimization of an aircraft hot-air anti-icing system based on Reduced Order Method

Geometric optimization of piccolo tube provides a cost-effective approach to shorten the design circle of hot-air anti-icing system and maximize the utilization efficiency of bleed air. An optimization methodology for aircraft hot-air anti-icing systems based on Reduced Order Method (ROM) is developed. ROM based on Proper Orthogonal Decomposition (POD) and Radial Basis Function neural network (RBF) is constructed to evaluate objective and constraint functions of single- and multi-objective optimizations. POD is adopted for data compression and characteristics extraction for the anti-icing performance snapshot matrix. Then, a lower-dimensional approximation for the snapshot matrix is derived from the projection subspace consisting of a set of basis modes. RBF neural network is introduced to construct the mapping between the design variables of piccolo tube geometric configuration samples and the linear combination coefficients of basis modes. The piccolo tube is parameterized by five design variables and is optimized by the developed methodology. The predicted results indicate that the constructed ROM can provide the distributions of surface temperature and runback water with high accuracy and computational efficiency. The optimal results indicate that the developed optimization methodology is efficient and reliable for handling single- and multi-objective design problems of aircraft piccolo tube hot-air anti-icing systems.

Hot-Air Anti-Icing Heat Transfer and Surface Temperature Modeling

An inlet strut with a hot-air anti-icing system is studied experimentally and numerically to understand the heat transfer between impinged supercooled water droplets and solid surfaces. Experiments were performed in an icing research wind tunnel for dry (without water droplets) and sprayed cases. The results show that the impinged droplets can decrease the surface temperature, even on areas without droplet impingement or a water film. Theoretically, the impinged droplets exchange heat with solid surfaces through two heat flow rate terms: , which contains the kinematic and internal energies of the impinged droplets; and the evaporation energy . Adding these two terms to the solid surface when simulating the dry case provides a method to predict the surface temperature after spraying. Calculations for depend on the film coverage that varies due to different operating conditions. However, calculating for the impinged area or over the entire surface can give the upper and lower bounds of the prediction for surface temperature. The results show that both methods can give predictions with errors that are below 5% for all cases studied. The numerical results also show that both and decrease the surface temperature, whereas the effect of is neglectable when compared with .

Design and characterization of trabecular structures for an anti-icing sandwich panel produced by additive manufacturing

The need for a high-efficiency hot air anti-icing system is met by the use of sandwich panels with high surface area trabecular structures as core. Trabecular structures have good mechanical properties and are able to act as thermal exchange and structural support. A structural characterization of complex trabecular structures made by Additive Manufacturing is required. For this study, AlSi10Mg specimens were produced by Selective Laser Melting technology varying cell shapes (with or without vertical struts), cell sizes (4 and 5 mm) and struts size (1 and 1.2 mm). Compressive tests were performed on the specimens and fracture mechanisms for the two cell types were analyzed by optical microscope observation. The rupture modes of the specimens are strongly dependent on the cell shape as shown by the mechanical results and confirmed by comparison with the Gibson–Ashby model.

Effect of pin fin arrangement on the heat transfer characteristics in a convergent channel with impingement

The protection of the inlet components of an aircraft engine from the adverse effects of ice accretion has been a crucial design problem since the very early years of flight. Therefore, the configuration with efficient heat transfer is the focus on the design of a hot-air anti-icing system in an aero-engine. This paper studies experimentally on the heat transfer in a convergent channel with pin fins within the strut. Experiments are carried out by using a transient liquid crystal technique. The pitch ratio (D/d, where D is the diameter of the pin fins) of the pin fins and impingement hole, the dimensionles lateral distance (S/d, where S is the distance between the leading edge and pin fins, d is the diameter of the impingement hole) as well as the dimensionless vertical distance (S1/d, where S1 is the distance between pin fins) are respectively investigated to study the heat transfer on the surface of convergent channel. The Reynolds number based on the hydraulic diameter of the impingement hole ranges from 6300 to 12700. Within the experimental range, the result shows that the increasing pitch ratio D/d leads to a lower Average Nusselt Number, the Average Nusselt Number has the highest value when D/d = 1/3. The Average Nusselt Number increases at first and then decreases as the dimensionless lateral distance S/d increases, the Average Nusselt Number has the highest value when S/d = 2.5. When the dimensionless vertical distance S1/d increases, the Average Nusselt Number goes up at first and then reduces, the Average Nusselt Number has the highest value when S1/d = 3. The Average Nusselt Number increases as the Reynolds number increases.

Temperature and Runback Ice Prediction Method for Three-Dimensional Hot Air Anti-Icing System

A prediction method of surface temperature and runback ice for a three-dimensional hot air anti-icing system was proposed. Computational approach to realize this method was introduced. Both the external and internal flows were separately calculated, results of which were set as boundary conditions of heat conduction computation in airfoil skin. The results of external and internal flow calculations show that the effect of surface temperature on convective heat transfer coefficients and local droplet collection efficiency is negligible and the calculations can be decoupled. The prediction method based on heat flux was used to calculate surface temperature and runback ice results. The results show that, the effects of LWC and Mach number are much more significant than the effect of external flow temperature. The surface temperature at impinging interaction point is more sensitive to the change of external conditions than that at stagnation point. The surface temperature changes significantly with changing Mach number because both the mass rate of droplet and the impact limit are changed.

A new anti-icing method for an aero-engine nose cone

Ice accretion may occur on the entry components of an aero-engine under certain weather and flight conditions, which would lead to the deterioration of the engine performance and even severe safety problems. Anti-icing systems have been used including hot air anti-icing system, which consumes high pressure air from the compressor, and electronic heating system, which consumes high grade electronic energy. Compared with the traditional anti-icing methods, an efficient and low energy consumption anti-icing technique based on the rotating heat pipe (RHP) has a great advantage and good application potential, which utilizes the waste heat of the aero-engine. Until now, however, the mechanism of the heat transfer in a RHP has not been clearly revealed yet, due to the complexity of the two phase flow and phase change process occurred in the RHP, which makes it difficult to establish the design method for the aero-engine anti-icing system based on a RHP. Furthermore, the feasibility of the anti-icing system based on a RHP has not been confirmed by experiments. Therefore, the present work is focused on the theoretical and experimental investigations on the rotating nose cone anti-icing technique based on a RHP, in order to explore the two phase flow and heat transfer mechanism of such an anti-icing system, and to reveal the effects of different parameters on the performance of the system, which may provide the theory basis for the design of the nose cone anti-icing system based on a RHP. Furthermore, it is expected that the feasibility of the anti-icing system based on a RHP can be confirmed by the experiments on a prototype, providing the basis for the engineering applications.

Chordwise attenuation of heat transfer performance on inner surface of hot-air anti-icing system

Chordwise attenuation of heat transfer performance on inner surface of hot-air anti-icing system

Thermal Analysis and Testing of Nonrotating Cone with Hot-Air Anti-Icing System

A hot-air film-heating method designed for the anti-icing system of a small aeroengine cone is studied as well as an experimental study on its performance. Experiments are conducted under different icing conditions and hot air parameters in an icing wind tunnel, using a full-scale experimental cone model of a small aeroengine. The temperature distributions on the cone surface are measured by thermocouples. Experiment results show that the hot-air film anti-icing method is effective for the cone leading edge. Also presented is a numerical simulation of the temperature distribution of the aeroengine cone under icing condition. The flowfield around the cone is obtained by computational-fluid-dynamics code. The trajectories of supercooled water droplets and the collection efficiency are calculated by the Lagrangian approach. The coupling effects of heat transfer and mass transfer are considered in the temperature computation of the cone. The thermal analysis model considers the mass balance of water and energy balance on the surface of the cone. The simulation results are compared to the experiment measurements. The characteristics of the hot-air film-heating anti-icing method are also discussed.

Enhanced Heat Transfer with Short Pin Fins in Hot-Air Anti-Icing System

A new rectangular anti-icing structure with short pin fins is presented in this paper. Detailed experimental research is applied to discussing its heat transfer and enhancement characteristics. The results show that, heat transfer of this anti-icing structure enhances obviously, and the core factor for enhancement is the volume ratio occupied by pin fins in rectangular channel of anti-icing structure.

Solution for Aircraft Anti-Icing System Simulation by a Modified Perturbation Method

A solution of the surface temperature and the runback water mass flow rate distributions along the body contour for an electrothermal or a hot-air anti-icing system of an aircraft, when water droplets impinge on the surface, is obtained by a modified perturbation method. In the method, a small dimensionless parameter a that represents the ratio of the external convective heat transfer rate from the airfoil surface to the internal heating rate is used. Because of the high nonlinearity in the energy equation, obtaining a convergent solution by normal use of the perturbation method is virtually impossible. To improve the convergence properties of the solution, the calculation procedure is modified. The main idea behind the modification is splitting of the nonlinear term into linear and nonlinear terms and introducing a new variable e, by which a in each linear term is replaced. These modifications of the perturbation method help reduce the contribution of the nonlinear term, which drastically improves the convergence characteristics of the solution. The solutions agree well with the results obtained by the Runge-Kutta method and experimental and numerical results found in literature.

Numerical Heat Transfer Correlation for Array of Hot-Air Jets Impinging on 3-Dimensional Concave Surface

Numerical heat transfer correlations established from a numerical computational fluid dynamics (CFD) study of a three-dimensional hot-air jet array impinging on curved (circular) surface are presented. The results are in the form of numerical correlations for the average and maximum Nusselt number for different nozzle-to-nozzle spacing, nozzle-to-surface height, and hot-air jet Mach numbers typical of those in an hot-air antiicing system employed on aircraft wings. A validation case is presented, and it is shown that the results obtained from the CFD study are in good agreement with experimental data found in the literature. An interpolation technique, the Dual-Kriging method, that makes use of the numerical database for antiicing simulation on aircraft wings is presented. The benefit of using the Dual-Kriging method is that it preserves the nonlinear nature of the heat transfer distribution from a hot-air jet impinging on a curved surface.

Anti-Icing System Simulation Using CANICE

A mathematical model of a hot air anti-icing system and its implementation in the ice accretion simulation code CANICEarepresented.Theicing codeisusedto predictthesurfacetemperatureandtheamount ofrunbackwater for given atmospheric conditions and heat e ux distribution from an anti-icing device. The external boundary layer is modeled with an integral method. Velocity and temperature distribution in the water e lm are estimated using a polynomial approximation. Conduction in the airfoil skin is taken into account with a one-dimension model. Numerical results are compared with experimental and numerical results from NASA for three different icing conditions. The comparison shows that surface temperatures are very sensitive to the water droplet impingement limits. The integral method used here failed to predict correctly the heat transfer coefe cients in the transition region of the boundary layer. When experimental heat transfer coefe cients are used, the model gives satisfactory results.

Thermal analysis of engine inlet anti-icing systems

A hot air anti-icing system of a gas turbine engine inlet is analyzed numerically. A three-dimensional potential flow code, which accounts for compressibility effects, is used to determine the flowfield in and around the inlet. A particle trajectory code is developed using a local linearization technique. The trajectory code is used to calculate local water impingement rates. Energy balances are performed on both the surface runback water and the metallic skin to determine their temperature distributions. A variety of test cases are considered in order to validate the various numerical components of the process as well as to demonstrate the procedure.

Analysis of an airplane windshield anti-icing system using hot air

This paper documents the analysis methods developed to predict the performance of the windshield hot air anti-icing system on a business jet airplane. Flight data gathered from dry air and natural icing tests are used to develop and verify the accuracy of a procedure that will predict the windshield surface temperature for either wet or dry air. It is shown that windshield surf ace temperatures can be estimated to an accuracy of ±5% for a wide range of aircraft conditions. It is demonstrated that the method is somewhat conservative for all conditions.