Anti-icing System Research Articles

Efficiency of a Hot Air Curtain Provided by Fan-Shaped Holes for Anti-Icing Systems of Aircraft and Their Engines

Efficiency of a Hot Air Curtain Provided by Fan-Shaped Holes for Anti-Icing Systems of Aircraft and Their Engines

Effects of Upstream Component and Air Injection on Water Droplet Impingement Characteristics for Downstream Surfaces

Water droplet changes its movement direction and velocity when it bypasses an aircraft component with the surrounding airflow or gets blown by air injection from the inner part. When the deflected droplet impacts on the downstream surface, its impingement characteristics would be different from those without the frontal effects. In this article, a Lagrangian method was developed to include those upstream effects on the droplet collection efficiency. Validation cases were carried out for a cylinder and an MS (1)-0317 airfoil, whereas a multielement airfoil and an engine cone with a hot air film-heating anti-icing system were computed to investigate the effects of the upstream component and air injection on the impingement characteristics of downstream surfaces. It is found that the present collection efficiencies are in good agreement with the experimental data and the simulation results obtained by the Eulerian and traditional Lagrangian methods when not affected by those upstream factors. The droplet deflections and trajectory crossings are observed clearly under the influence of the upstream component, and the Lagrangian results of downstream surfaces differ from those of the Eulerian method. In addition, due to the air injection from the inner engine cone, the peak collection efficiency on the cone surface increases with the decrease of the droplet diameter and the value even exceeds one when the droplet is small. This work is helpful for the understanding of the droplet motion and the accuracy of aircraft icing simulation.

Numerical investigation of an anti-icing method on airfoil based on the NSDBD plasma actuator

PurposeThis paper aims to investigate the anti-icing performance of the nanosecond dielectric barrier discharge (NSDBD) plasma actuator.Design/methodology/approachWith the Lagrangian approach and the Messinger model, two different ice shapes known as rime and glaze icing are predicted. The air heating in the boundary layer over a flat plate has been simulated using a phenomenological model of the NSDBD plasma. The NSDBD plasma actuators are planted in the leading edge anti-icing area of NACA0012 airfoil. Combining the unsteady Reynolds-averaged Navier–Stokes equations and the phenomenological model, the flow field around the airfoil is simulated and the effects of the peak voltage, the pulse repetition frequency and the direction arrangement of the NSDBD on anti-icing performance are numerically investigated, respectively.FindingsThe agreement between the numerical results and the experimental data indicates that the present method is accurate. The results show that there is hot air covering the anti-icing area. The increase of the peak voltage and pulse frequency improves the anti-icing performance, and the direction arrangement of NSDBD also influences the anti-icing performance.Originality/valueA numerical strategy is developed combining the icing algorithm with the phenomenological model. The effects of three parameters of NSDBD on anti-icing performance are discussed. The predicted results show that the anti-icing method is effective and may be helpful for the design of the anti-icing system of the unmanned aerial vehicle.

Using Heat Pumps to Improve the Efficiency of Combined-Cycle Gas Turbines

This paper studies the integration of heat pump units (HPUs) to enhance the thermal efficiency of a combined heat and power plant (CHPP). Different solutions of integrate the HPUs in a combined-cycle gas turbine (CCGT) plant, the CCGT-450, are analyzed based on simulations developed on “United Cycle” computer-aided design (CAD) system. The HPUs are used to explore low-potential heat sources (LPHSs) and heat make-up and return network water. The use of HPUs to regulate the gas turbine (GT) intake air temperature during the summer operation and the possibility of using a HPU to heat the GT intake air and replace anti-icing system (AIS), over the winter at high humidity conditions were also analyzed. The best solution was obtained for the winter operation mode replacing the AIS by a HPU. The simulation results indicated that this scheme can reduce the underproduction of electricity generation by the CCGT unit up to 14.87% and enhance the overall efficiency from 40.00% to 44.82%. Using a HPU with a 5.04 MW capacity can save $309,640 per each MW per quarter.

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.

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 .

Impacts of Thermal and Mechanical Cycles on Electro-Thermal Anti-Icing System of CFRP Laminates Embedding Sprayable Metal Film.

The aircraft electro-thermal anti-icing system that can guarantee flight safety may be affected by periodic heating and cyclic aerodynamic force during long-term flight missions, which seems to be a potential threat to ice protection. This paper aims to investigate the impacts of thermal and mechanical cycles on heating elements of the electro-thermal anti-icing system. Specimens were manufactured with CFRP (carbon fiber reinforced polymer) laminated composite, glass fiber prepreg and copper screen, in which sprayable metal film (SMF) was embedded as the heating element. The study focuses on electric resistance variation of SMF and functional fatigue life under the cycling load. Thermal cycling tests were carried out in an insulated chamber where the specimens were heated up to 80 °C and then cooled down to −55 °C for 1000 cycles. Mechanical cycling tests were conducted on a fatigue testing machine where the specimens were imposed on tension-compression loading for 106 cycles. Results showed that the electric resistance of SMF increased with the number of loading cycles. The resistance was increased by 20% and the heating power was decreased by 16.67% after 1000 thermal cycles. During the mechanical cycling tests, it was found that the heating element was destructed before the structural failure, which indicated that the fatigue life of function was lower than that of the structure.

Effects of flow parameters on thermal performance of an inner-liner anti-icing system with jets impingement heat transfer

The multiple jets impingement heat transfer is widely applied in the wing anti-icing system. It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior. In the present study, the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m × 3 m icing wind tunnel of China Aerodynamics Research and Development Center. The effects of icing parameters Liquid Water Content (LWC) and Median Volume Diameter (MVD) and hot air parameters (mass flow rate and temperature) on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied. The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms. The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters. The temperature of impingement hot air and that of wing skin are approximately linear correlated. The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion. The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.

Refillable anti-icing SBS composite films

The lifetime of release-based anti-icing systems can be improved by refilling after the complete release of active agents. A novel swelling mediated consecutive filling of Diatomaceous Earth (DE) loaded Styrene-Butadiene-Styrene (SBS) composite films with PEG for anti-icing applications is reported. The degree of swelling and the diffusion of active agents into the composite was controlled by adjusting the composition of a binary mixture consisting of a non-solvent (acetone) and a good solvent (diethyl ether (DiEt)). Rhodamine 6G was used as a probe to show the extent of diffusion of dissolved molecules into SBS. The reversible loading of PEG-600 as anti-icing agent up to 19% by weight into DE/SBS composites and the complete release in the binary mixture having 30 vol. % DiEt was successfully achieved in consecutive cycles. After the 5th loading cycle, these composite films exhibited similar water contact angles (∼ 64°) and freezing delay times within error bars as those of the 1st loading cycle. At −15 °C, the average freezing delay time of the water droplets on DE/SBS composites filled with PEG in 30 vol. % DiEt was increased by a factor of three to 120 s. The successful refilling of the composites with reversible loading/release cycles and without any deterioration in the anti-icing properties at least up to 5 cycles is a significant contribution to the lifetime of release based functional coatings.

Considerations regarding the anti-icing system for the ship propulsion plant with gas turbine

Vessels that have navigation routes in areas with ambient temperatures that can drop below + 5 [°C], with a relative humidity of over 65%, will have implemented technical solutions for monitoring and combating ice accumulations in the intake routes of gas turbine power plants. Because gas turbines are not designed and built to allow the admission of foreign objects (in this case - ice), it is necessary to avoid the accumulation of ice through anti-icing systems and not to melt ice through defrost systems. Naval anti-icing systems may have as a source of energy flow compressed air, supersaturated steam, exhaust gases, electricity or a combination of those listed. The monitoring and optimization of the operation of the anti-icing system gives the gas turbine power plant an operation as close as possible to the normal regimes stipulated in the ship's construction or retrofit specification.

Application of different Lagrangian Particle Tracking techniques for water impingement

Water impingement on aerodynamic surfaces represents how much flow rate water mass impact on the surfaces, respect to total mass flow rate. This parameter, together with Liquid Water Content, is important in ice prediction since it defines water mass distribution on solid surface, by which depends several other problems like freezing fraction, anti-icing system, etc. In this work we focus on the lagrangian method to calculate droplets’ trajectory, comparing the results against 2D and 3D experimental data.

Convolutional neural network with dual inputs for time series ice prediction on rotor blades of wind turbines

Downtimes due to ice formation on rotor blades reduce the economic efficiency of wind turbines. An accurate ice prediction is required to operate active de-icing measures such as blade heating as an anti-icing system. Building upon our previous research, this paper proposes the use of a convolutional neural network model with dual inputs and one-dimensional convolution filters using historical data from the wind turbine as well as weather forecasts to predict the ice situation for the next 24 hours. The model is validated using data from three different wind farms and shows an average balanced accuracy of 97.9%.

Increasing the economic sustainability of winter road maintenance processes through the use of technological innovation

Effective road management requires the constant generation of new approaches. It is our duty to focus on improving all technical and process areas of road management, especially in the context of environmental and economic sustainability. Otherwise, we will face the fact that neglected parts will slow down the progress of the whole system. This will be reflected in a reduction in the quality of the infrastructure and increased costs over its life cycle. The approach must be systematic and therefore it is necessary to address the elements that, at first sight, do not have a major impact on other elements contained in the whole structure of road infrastructure management. One of the key areas for improvement is the process of winter road maintenance. It must reflect global climate change, new approaches to the cost-effectiveness of finances spent by users and road managers and, last but not least, the need for modern and safe mobility of goods and people. Advanced technologies such as automated anti-icing spraying systems or predictive monitoring of road structure temperature development are one example. However, these innovations bring not only positive but also negative effects.

Numerical procedure for electro-thermal anti-icing system simulation coupling internal thermal analysis and external multi-physic code

The present work has the aim of coupling two codes, one able to perform icing simulations and another one capable to simulate the performance of an electro-thermal anti-icing system in an integrated fashion. In fact, the classical tool chain of icing simulation (aerodynamics, water catch and impact, mass and energy surface balance) is coupled to the thermal analysis through the surface substrate and the ice thickness. In general, the substrate consists of a multi-layered composite with different properties for each layer and embedded heaters (resistors) at interfaces between layers. In the present approach, the ice protection simulation is not decoupled from the ice accretion simulation, but a single computational workflow is considered. Validation results obtained on benchmark test cases from NASA database will be detailed as well as comparison with numerical results from other authors.

3D printed anti-icing and de-icing system based on CNT/GNP doped epoxy composites with self-curing and structural health monitoring capabilities

The strain-sensing, self-curing and self-heating capabilities of a 3D printed circuit made of a graphene nanoplatelet and carbon nanotube reinforced resin, have been widely explored. These materials exhibit high Joule’s heating effect capabilities that can be used for post-curing processes. More specifically, the values of glass transition temperature reached by Joule’s heating post-curing were very similar to those obtained by conventional oven heating. The temperature profile along each individual ribbon was relatively homogeneous, being an indicative of a good nanoparticle dispersion, confirmed by field emission gun scanning electron microscope analysis. Furthermore, the proposed printed circuits showed excellent strain-sensing capabilities with a much higher strain sensitivity, with a gauge factor of 6–8, in comparison to conventional metallic gauges or bulk nanocomposites, with a gauge factor of around 2, showing also good linearity. In addition, the breakage of individual ribbons can be easily detected by the strain-sensing system as a sharp increase of the electrical resistance. Finally, temperature compensation tests showed that, in case of printed ribbon breakage, it is possible to keep constant the average temperature of the circuit by raising the applied voltage to avoid ice accretion. Thus, with none to two broken ribbons, the 3D printed circuit can act as an efficient anti-icing and de-icing system.

Optimal Plate Heat Exchangers of Power Generation Systems

Plate heat exchangers are an effective type of heat exchange equipment and can be used in many power plants. The article analyzes the use of corrugated plate heat exchangers in a number of installations. Their optimization was done according to the economic criterion of optimality, taking into account capital investments and operating costs. The analysis of the plate heat exchangers uses as oil coolers (a number of loads with oil mass flow rates 10….250 kg/s) and water heaters (heat power 100…2000 kW) of steam turbine plants. It has been established that plate oil coolers are more economical than shell-and-tube ones. Also, the anti-icing system plate air heaters of gas turbine plants with a power of 1 to 20 MW considered. The air for the anti-icing system was taken after the compressor and was additionally heated by exhaust gases. It has been established that it is necessary to install an additional flue gas smoke exhauster for using plate heat exchangers. Air must be extracted after the compressor, otherwise, low air density leads to high hydraulic losses, which makes it impossible to use plate heaters. Optimum air velocities are in the range of 0.4…0.6 m/s, flue gas velocities are 4…6 m/s. The use of standard plate heat exchangers with corrugated plates is impractical for GTU powers above 5 MW. Optimization of plate regenerators of supercritical CO2 cycles with recompression for powers from 1 to 15 MW has been done. Optimum velocities of hot CO2 are about 0.8 m/s, cold ones 0.3…0.5 m/s. The optimal sizes of plate heat exchangers are recommended for all of the above applications.

Investigation on the Mechanism of Heat Load Reduction for the Thermal Anti-Icing System

The aircraft ice protection system that can guarantee flight safety consumes a part of the energy of the aircraft, which is necessary to be optimized. A study for the mechanism of the heat load reduction in the thermal anti-icing system under the evaporative mode was presented. Based on the relationship between the anti-icing heat load and the heating power distribution, an optimization method involved in the genetic algorithm was adopted to optimize the anti-icing heat load and obtain the optimal heating power distribution. An experiment carried out in an icing wind tunnel was conducted to validate the optimized results. The mechanism of the anti-icing heat load reduction was revealed by analyzing the influences of the key factors, such as the heating range, the surface temperature and the convective heat transfer coefficient. The results show that the reduction in the anti-icing heat load is actually the decrease in the convective heat load. In the evaporative mode, decreasing the heating range outside the water droplet impinging limit can reduce the convective heat load. Evaporating the runback water in the high-temperature region can lead to the less convective heat load. For the airfoil, the heating power distribution that has an opposite trend with the convective heat transfer coefficient can reduce the convective heat load. Thus, the optimal heating power distribution has such a trend that is low at the leading edge, high at the water droplet impinging limit and zero at the end of the protected area.

Skill and Potential Economic Value of Forecasts of Ice Accretion on Wind Turbines

AbstractIn this paper, a verification study of the skill and potential economic value of forecasts of ice accretion on wind turbines is presented. The phase of active ice formation on turbine blades has been associated with the strongest wind power production losses in cold climates; however, skillful icing forecasts could permit taking protective measures using anti-icing systems. Coarse- and high-resolution forecasts for the range up to day 3 from global (IFS and GFS) and limited-area (WRF) models are coupled to the Makkonen icing model. Surface and upper-air observations and icing measurements at turbine hub height at two wind farms in central Europe are used for model verification over two winters. Two case studies contrasting a correct and an incorrect forecast highlight the difficulty of correctly predicting individual icing events. A meaningful assessment of model skill is possible only after bias correction of icing-related parameters and selection of model-dependent optimal thresholds for ice growth rate. The skill of bias-corrected forecasts of freezing and humid conditions is virtually identical for all models. Hourly forecasts of active ice accretion generally show limited skill; however, results strongly suggest the superiority of high-resolution WRF forecasts relative to other model variants. Predictions of the occurrence of icing within a period of 6 h are found to have substantially better accuracy. Probabilistic forecasts of icing that are based on gridpoint neighborhood ensembles show slightly higher potential economic value than forecasts that are based on individual gridpoint values, in particular at low cost-loss ratios, that is, when anti-icing measures are comparatively inexpensive.

3D printed epoxy-CNTs/GNPs conductive inks with application in anti-icing and de-icing systems

This paper studies the development and characterization of 3D printed conductive circuits based on epoxy inks doped with carbon nanotubes (CNTs) and/or graphene nanoplatelets (GNPs), which could be used in applications such as electronic circuits, heated seats, Anti-icing and De-Icing Systems (ADIS) or Structural Health Monitoring (SHM) systems, among others.A design of experiments (DOE) has been carried out by the Taguchi method to develop and optimize an ADIS based on a 3D printed circuit, using a conductive ink doped with CNTs/GNPs to achieve Joulés heating. The target of the DOE is based on reaching the highest average temperature, which was measured by infrared thermographic analysis, taking also into account the quality of the 3D printed circuits. The DOE factors were the CNT and GNP content, the voltage applied to the circuit and its geometry, proposing two alternative designs.Finally, a de-icing test was carried out with the optimal parameters obtained from the DOE. Results evince the viability of the system developed, being able to melt an ice layer of 2.5 mm thick in 3 min and 30 s.

Investigation of the thermal parameters of an aluminum heater with nanoporous alumina

An important task faced in the industry of permanently installed heating systems addressed by a large number of manufacturers is power saving. Heating systems may have variegated designs, yet there are basic design requirements, i.e., high operational reliability, resource saving, environmental resistivity and stability of electric parameters. The key component of any heating unit is the heater. Flat resistive heaters have found wide application in heating units aimed at sustaining healthy indoor microclimate, maintaining preset process parameters on industrial premises, as well as in anti-icing systems, agriculture and general industry. We studied the thermal parameters of flat aluminum heating units containing carbon fiber ribbon heaters. To ensure the required insulation of the heater from the metallic base plate, the aluminum surface had a 20 mm thick porous aluminum oxide layer. The ends of the carbon fiber were metalized with a layer of copper for further soldering upon integration into the electric heating unit assembly. The electrical resistance of the heater with a carbon fiber was 60 Ohm. The propagation of heat flows inside a plate of aluminum with nanoporous aluminum oxide was studied using thermal imaging measurements. Temperatures on the surface of the aluminum heater cover and on the opposite heat emitting side were shown as a function of heating time. The experimental results suggest that the heat generated by the linear carbon fiber heater distributes rapidly in the entire bulk of the aluminum heater plate. This indicates a high heat conductivity of the heater aluminum base plate whose parameters provide for the required thermal parameters of the heating unit.