Browse Topic: Icing and ice detection

Items (290)
Find
Water Spray and High Humidity Endurance Test Methods for AMS1424 and AMS1428 Aircraft Deicing/Anti-Icing FluidsAS5901E (Current)11/26/2025
This document establishes the minimum requirements for an environmental test chamber, and test procedures to carry out anti-icing performance tests according to the current materials specification for aircraft deicing/anti-icing fluids. The primary purpose for such a test method is to determine the anti icing endurance under controlled laboratory conditions of AMS1424 Type I and AMS1428 Type II, III, and IV fluids.
G-12ADF Aircraft Deicing Fluids
Numerical Analysis of Rotor Aero-acoustic Characteristics for Ice Detection based on the HMB SolverF-0074-2018-127105/7/2024
ABSTRACT In this work, iced rotors are studied to develop insight in the potential of acoustics-based ice detection. Based on the HMB CFD solver, approximate iced shapes are used and results are analyzed using the FW-H method. Several candidate monitoring positions are assessed for acoustic sensors to be placed on the helicopter fuselage. The influence of ice on the aero-acoustic characteristics of a rotor is calculated, and parameters such as the ice amount and the icing position on the blade are quantified.
Chen, Xi, Barakos, George, Zhao, Qijun
Rotor Icing and De-icing at DLR's Whirl Tower Test FacilityF-0080-2024-13175/7/2024
The paper presents recent and ongoing activities of the German Aerospace Center (DLR) focusing on experimental icing investigations within the nationally funded project InTEnt-H (2018-2022) and progressive activities in continuing internal DLR projects. The aim of InTEnt-H was to investigate innovative de-icing and anti-icing technologies for small and medium-weight helicopters, for which no rotor de-icing technologies exist to date, and to demonstrate the effectiveness of these systems in a suitable test facility. For this purpose, the whirl tower test facility of the DLR in Braunschweig has been converted into an icing test facility that is unique in Europe and will allow for the generation of atmospheric icing conditions. In this facility, de-icing and anti-icing systems for rotor blades can be tested under centrifugal loads and various icing conditions. The paper starts with a short presentation of the retrofitting works at the DLR whirl tower test facility and its major components. Then, the progress of the first test campaigns of the projects are reported. The main focus is on the design and test of the de-icing rotor system, carrying different antiicing/ de-icing technologies. The paper closes with an outlook on the upcoming activities planned to satisfy and verify EASA CS-29 Appendix C icing conditions in the frame of the DLR internal project SAFER2.
Bartels, Rainer, Konrath, Robert, Keimer, Ralf, Sahyoun, Dominic, Schneider, Oliver, Kalow, Steffen
Control Margin Awareness of the AW609 TiltRotor under Asymmetric Aerodynamic Flight ConditionsF-0074-2018-127915/7/2024
ABSTRACT The ability to model and evaluate aircraft performance prior to flight has generated a significant increase in safety margin in the flight testing of experimental aircraft. Prior to the artificial icing campaign for the AW609 aircraft, a flight model of predicted aerodynamic behavior was used to rapidly generate a control margin monitoring and warning system, which was implemented on-board the aircraft during testing to provide awareness of predicted aircraft behavior under icing conditions.
Xiao, Sid, Belt, David, D'Ettorre, Pietro, Edwards, Paul
Drag Performance Degradation Due to Icing of eVTOLF-0078-2022-175335/10/2022
ABSTRACT
McKillip, Robert, Karli, Geoffrey, Yan, Sihong, Palacios, Jose
eVTOL Accretion Modeling for Supporting Algorithmic Icing DetectionF-0076-2020-1629710/5/2020
eVTOL aircraft operating within the air transportation system will undoubtably be exposed to inclement and adverse weather conditions, which may well include operation in icing conditions, whether planned or encountered inadvertently. Design compromises necessary to provide VTOL operations may make continued operation in an icing environment particularly challenging, especially for eVTOL aircraft having only limited excess power for operation of anti-icing or deicing equipment. This paper describes a research program to assess the impact of accreted icing on the performance of eVTOL aircraft, as part of a program for implementation of an Icing Detection Filter that leverages detailed knowledge of that performance impact on the distributed electrical propulsion and lift systems on the vehicle. Modeling approaches for prediction of icing accretion and the associated performance losses, particularly as they can be measured through monitoring of the onboard electrical power system, are described.
Jr., Robert, Kaufman, Andrew, Quackenbush, Todd
Prevention of Snow Accretion on Camera Lenses of Autonomous Vehicles2020-01-01054/14/2020
With the rapid development of artificial intelligence, the autonomous vehicles (AV) have attracted considerable attention in the automotive industry. However, different factors negatively impact the adoption of the AVs, delaying their successful commercialization. Accretion of atmospheric icing, especially wet snow, on AV sensors causes blockage on their lenses, making them prone to lose their sight, in turn, increasing potential chances of accidents. In this study, two different designs are proposed in order to prevent snow accretion on the lenses of AVs via air flow across the lens surface. In both designs, lenses made of plain glass and superhydrophobic coated glass surfaces are tested. While some researchers have shown promise of water repellency on superhydrophobic surfaces, more snow accretion is observed on the superhydrophobic surfaces, when compared to the plain glass lenses. In the experiments, snow is formed using a novel snow gun inside a walk-in cold room connected to a wind tunnel that can reach wind speeds of up to 40 mph. It is observed that the air flow over the lens significantly reduces the accretion of snow on the lens and could maintain the lens clean for up to 20 mph wind velocities. However, at LWC values of approximately 28%, the stickiness of the snowflakes increases, enhancing snow accretion on the lenses and translating to significant loss of sight. The high stickiness of the snowflakes along with high wind speeds leads to increased blockage of the AV lenses.
Mohammadian, Behrouz, Sarayloo, Mehdi, Heil, Jamie, Sojoudi, Hossein, Robertson, Michael, Hong, Haiping, Tran, Tommy, Patil, Sunil, Krishnan, Venkatesh
Sensor Uses Microwaves to Determine Real-Time Ice AccumulationTBMG-361953/1/2020
A sensor detects the precise moment when ice begins to form on a surface. Due to their high sensitivity, low power, ease of fabrication, and planar profile, microwave resonators were chosen for the device.
EquipmentAS6286/2A (Current)11/8/2019
This document covers the standards of de-icing/anti-icing equipment. In conjunction with the main document and other related slash sheets it will provide guidelines for the proper procedures to deice and anti-ice aircraft on the ground information to support this training program is provided to make the material a better tool for the preparation and execution of the training & qualification. It is intended to provide a common basis for de-icing/anti-icing training and qualification for de- icing providers and airlines. This material was compiled using various international documents with support from SAE documents and individually contributed editorial comments. Its purpose is to serve as a "Globalized Deicing Training Manual".
G-12T Training and Quality Programs Committee
Compensating the Effects of Ice Crystal Icing on the Engine Performance by Control Methods2019-01-18629/16/2019
Aircraft equipment is operated in a wide range of external conditions, which, with a certain combination of environmental parameters, can lead to icing of the engine internal elements. Due to icing, the engine components performance characteristics change what leads to decrease in thrust, gas dynamic stability, durability, etc. Safe aircraft operation and its desired performance may be lost as a result of such external influence. Therefore, it is relevant to study the possibilities of reducing the icing effect with the help of a special engine control. The focus of this paper is to determine control methods of an aircraft gas turbine engine addressing this problem. The object of the study is a modern commercial turbofan with a bypass ratio of about 9. In this paper analysis of the effect of ice crystal icing on the engine components performance is conducted. To perform simulation of the engine performance under such impact, degraded components characteristics was introduced into physics-based turbofan model. Control algorithms for this model were developed applied to various regulated variables used in the setpoint controllers of modern engines (fan speed, engine pressure ratio, etc.). It allowed to evaluate an engine operation in ice crystal condition with each kind of controller. Additionally, the engine control method using a thrust value provided by the on-board engine model is considered. Simulation showed the ability to maintain baseline thrust with degraded engine components performance. According to calculation results, an optimal engine control method which allow compensating the negative effect of ice crystal icing is determined.
Gurevich, Oskar, Smetanin, Sergei, Trifonov, Mikhail
An Experimental Study to Evaluate the Droplet Impinging Erosion Characteristics of an Icephobic, Elastic Soft Surface2019-01-19976/10/2019
Elastic soft material/surface, such as Polydimethylsiloxane (PDMS), is a perspective, useful and low-cost hydrophobic and icephobic coating. While it has been reported to have good mechanical durability, its erosion durability under the high impacting of water droplets pertinent to aircraft inflight icing phenomena has not been explored. In this study, the droplet imping erosion characteristics of an icephobic PDMS surface/material is evaluated systematically upon the dynamic impinging of water droplets at different impact velocities (~ up to 75m/s), in comparison with other state-of-the-art icephobic materials/surfaces, such as superhydrophobic surface (SHS) and slippery liquid-infused porous surface (SLIPS). Surprisingly, the contact angle (CA) of the elastic PDMS is shown to have an over 20° increase (from 105° to 128°), which represents better hydrophobicity, after the erosion test which is mainly contributed to the higher roughness of the eroded PDMS surface. As for the icephobicity evaluation, intact PDMS was found to has ultra-low ice adhesion (~8 kPa), in comparison with SHS (i.e., ~100kPa) and SLIPS (i.e., ~35kPa). PDMS also shows outstandingly stable ice adhesion during the erosion test (i.e., fluctuation only within ~4kPa) as a result of the growth of cracks on the PDMS surface and the increased surface energy.
Ma, Liqun, Zhang, Zichen, Liu, Yang, Hu, Hui
Advanced Nanocomposite Low Adhesion Icephobic Coating for Aerospace Applications2019-01-19966/10/2019
Icing is a major safety issue for flight operations in the civil, defense and space sectors. Ice can form on critical components during takeoff/landing, or while in service, depending on prevailing weather conditions. Aircraft manufacturers relies on two different approaches to prevent ice buildup using an active anti-icing system to melt ice buildup or deicing chemicals/ice repellent surface to minimize the buildup ice. The use of active anti-icing systems offers good protection, however can add significant penalty to overall weight, energy consumption and cost. Aerospace industry is in need for an advanced ice repellent surface to effectively minimize ice buildup on critical components with no modification to existing design can provide significant relief to ice prone systems. In this paper, Oceanit will present its most advanced nanocomposite low ice adhesion icephobic coating technology that was developed and demonstrated for application on metallic surfaces to provide the lowest ice adhesion to significantly reduce ice buildup. Oceanit’s advanced icephobic coating was tested to be one of the lowest ice adhering coating (ice adhesion strength = 5.1kPa) ever tested and evaluated by US Army Cold Regions Research and Engineering Lab (CRREL). The following paper will provide in depth discussion on the characterization and applications of the icephobic coating relevant to aerospace industry.
Veedu, Vinod, Thapa, Sumil, Arumugam, Ganesh Kumar
Creation of an Icephobic Coating using Graphite Powder and PTFE Nanoparticles2019-01-19796/10/2019
Ice accretion can cause numerous inefficiencies, structural stresses, and failures in applications ranging from building design to power generation and aerospace applications. Currently, some of the leading de-icing technologies, such as the ICE-WIPS system, utilize a heating element coupled with a superhydrophobic surface. The high power consumption inherent in these systems can make them expensive and impractical, especially when coupled with power generating systems. Reduced power consumption in these de-icing technologies can be achieved through increased absorption of solar radiation in the visible range while maintaining hydrophobic performance of a coating. In this work, a Polytetrafluorethylene (PTFE) and graphite-based superhydrophobic surface is proposed, which maintains similar hydrophobic performance to standard superhydrophobic surfaces. The novel coating demonstrates contact angles of upwards of 130o and sliding angles of less than 4o, while increasing solar radiation absorption in the visible range by approximately 139% over PTFE-based hydrophobic coatings. Icing wind tunnel tests where the coatings were exposed to visible light in order to simulate solar radiation were performed in a variety of different conditions in order to verify the improved de-icing capabilities introduced by the added graphite. The melting time per unit ice mass was reduced by upwards of 50% for glaze ice and 8.0% for rime ice over a comparable de-icing coating without added graphite. There was also a qualitative difference in de-icing performance, as the coating with added graphite demonstrated removal of ice in a single sheet from the base layer, in contrast to the PTFE only coating, which allowed for the ice to melt in multiple pieces from the model.
Gonzales, Joseph, Sakaue, Hirotaka
Experimental and Computer Model Results for a Carbon Nanotubes Electrothermal De-Icing System2019-01-20056/10/2019
Results from a three-dimensional computer model of a Carbon Nanotubes (CNT) based de-icing system are compared to experimental data obtained at COLLINS-Ohio Icing Wind Tunnel (IWT). The experiments were performed using a prototype of a CNT based de-icing system installed in a section of a business jet horizontal tail. The 3D numerical analysis tools used in the comparisons are AIPAC [1] and CFD++. The former was derived from HASPAC, an anti-icing computer model developed at Wichita State University in 2010 [3, 9, 10]. AIPAC uses the finite volumes method for the solution of the icing problem on an airfoil leading edge (or other 3D surfaces) and relies on any CFD solver to obtain the external flow properties used as boundary conditions. AIPAC is capable of predicting 3D multi-step ice shapes under rime, glaze and mixed regimes, and can also deal with the complex dynamics of cyclic ice accretion, melting, and shedding present in the realm of aircraft electrothermal de-icing systems. The latter is the CFD solver selected to provide the external flow properties for the icing analysis presented in this paper. Comparisons of predicted vs. experimental leading edge temperatures along time as well as intercycle and runback ice accretions are provided. The numerical tools used have shown good agreement with the experiments, fairly capturing the locations of the ice accretions, which are important for aerodynamic degradation analysis, and keeping the airfoil skin temperatures predictions satisfactorily close to the experimental results.
Domingos, Rodrigo, Becker, Gilberto
Experimental Investigation of High Speed SLD Impact2019-01-20066/10/2019
This paper proposes an experimental investigation of fast impinging large droplets in non-icing conditions. Two main aspects of the impact event are analyzed and discussed: the impact dynamics as a function of the surface nature and the deposition rate of the liquid on the impingement surface for various conditions. The data has been recorded and characterized at ambient pressure and a temperature of the air between 5 and 10°C using a vertical wind/droplet tunnel. To avoid the droplets evaporation the relative humidity was controlled. The morphology of impact was studied by backlighted imagery and quantitative results were obtained by image analysis. The deposition rate was obtained weighting the water accumulated on the impingement plate. Examination of splashing events images obtained on a clean surface and on blotter paper shows important differences in terms of secondary drop generation. The measurement of the deposition rate confirmed that the dynamics of drop impingement on blotter paper is not the same as impingement on a clean surface. These differences may significantly impact the development of models for icing applications.
BODOC, Virginel, Berthoumieu, Pierre
Evaluation of Visual Failure versus Aerodynamic Limit for a Snow Contaminated Anti-Iced Wing Section during Simulated Takeoff2019-01-19726/10/2019
Under contract to Airlines for America (A4A), APS Aviation Inc. (APS), in collaboration with the National Research Council of Canada (NRC), completed an aircraft ground icing exploratory research project at the NRC 3 m × 6 m Wind Tunnel in Ottawa in January 2019. The purpose of this project was to investigate the feasibility of using aerodynamic data to evaluate the performance of contaminated anti-icing fluid, rather than the traditional visual fluid failure indicators that are used to develop Holdover Times (HOTs). The aerodynamic performance of a supercritical airfoil model with anti-icing fluids and snow contamination was evaluated against the clean, dry performance of the airfoil in order to calculate the associated aerodynamic penalty. The visual failure of the fluid was also evaluated for each run, and the visual and aerodynamic results were compared against each other for each contamination exposure time. The results demonstrated that the visual failure of a fluid was not directly linked to the aerodynamic performance of the fluid, and the margin between the two was a function of the fluid used, the model configuration, and the test temperature. The results support the premise that in specific operational conditions, certain fluids may offer protection for a period of time after the visual failure. This margin of protection is likely dependent on the same variables as the current holdover times, including precipitation type and intensity, fluid type, and outdoor air temperature and aircraft configuration.
Clark, Catherine, Ruggi, Marco
Equivalent Sand Grain Roughness Correlation for Aircraft Ice Shape Predictions2019-01-19786/10/2019
Many uncertainties in an in-flight ice shape prediction are related to convection heat transfer coefficient, which in turn depends on the flow, turbulence and laminar/turbulent transition models. The height of ice roughness element used to calculate the Equivalent Sand Grain Roughness height (ESGR) is a very important input of the turbulence model as it strongly influences the shape of the accreted ice. Unfortunately, for in-flight icing, the ESGR is unknown and generally calculated using semi-empirical models or empirical correlations based on a particular ice shape prediction code. Each ice shape prediction code is unique due to the models and correlations used and the numerical implementation. Ice roughness correlations do not have the same effect in each ice shape prediction code. A new approach to calculate the ESGR correlation taking into consideration the particularities of the ice shape prediction code is developed, calibrated and validated. This new approach derives a correlation based on two dimensionless numbers: the first by re-defining the Stanton number and the second based on the thermodynamic heat balance. A calibration procedure is used based on 14 different 2D experimental ice shapes for a NACA 0012 airfoil of 21 inches chord. The correlation is validated against 41 2D experimental ice shapes obtained on 5 airfoils: the GLC 305; a commercial transport airfoil; NACA 23014; NACA 0015 and NACA 0012. A large range of icing conditions are covered. The results of this validation exercise show 90% of the predicted ice shapes are visually in good to excellent agreement with experiment. The advantage of the proposed ESGR correlation for the calculation of the ice roughness is that the correlation is calibrated with only a few cases for a specific icing simulation suite. This is possible because the correlation depends on two dimensionless numbers related to the in-flight icing physics simulation.
Fortin, Guy
Measured Interfacial Residual Strains Produced by In-Flight Ice2019-01-19986/10/2019
The formation of ice on aircraft is a highly dynamic process during which ice will expand and contract upon freezing and undergoing changes in temperature. Finite element analysis (FEA) simulations were performed investigating the stress/strain response of an idealized ice sample bonded to an acrylic substrate subjected to a uniform temperature change. The FEA predictions were used to guide the placement of strain gages on custom-built acrylic and aluminum specimens. Tee rosettes were placed in two configurations adjacent to thermocouple sensors. The specimens were then placed in icing conditions such that ice was grown on top of the specimen. It was hypothesized that the ice would expand on freezing and contract as the temperature of the interface returned to the equilibrium conditions. While results from the aluminum specimens matched this hypothesis, results from the acrylic specimens show a short period of contraction followed by a much larger expansion at the interface, indicating more complex ice growth thermodynamics than anticipated. Some samples were observed to delaminate, suggesting that the residual strain is significant to the shedding of ice for in-flight applications.
Work, Andrew, Salem, Jonathan, Baker, Eric, Schirmer, Ernestina, Douglass, Rebekah, Kreeger, Richard
Focus on Challenges in SLD Regime: Reemitted Droplet Modelling2019-01-20016/10/2019
A lot of studies have been carried out over the last decades on SLD ice accretion challenges. Many of them referred to SLD physics modelling such as break-up, splashing, bouncing, etc… and relied on numerous physics experiments. Different models have been developed in Europe and North-America and have been implemented in several numerical tools, widely in 2D but more and more in 3D. As these tools are intended to be used increasingly among the community, deficiencies have to be deeper investigated. This paper provides some highlights on specific needs linked to SLD impingement and ice accretion, especially for 3D high fidelity computations. Regarding the results, deficiencies on the numerical side and on experimental needs will be highlighted in order to feed brainstorming for ongoing SLD projects such as in European Union H2020 ICE-GENESIS.
Caminade, Francois, Frazza, Loïc
An Experimental Study on the Effects of the Layout of DBD Plasma Actuators on Its Anti-/De-Icing Performance for Aircraft Icing Mitigation2019-01-20336/10/2019
Recently developed dielectric barrier discharge (DBD) plasma-based anti-icing systems have shown great potential for aircraft icing mitigation. In the present study, the ice accretion experiments were performed on to evaluate the effects of different layouts of DBD plasma actuators on their anti-/de-icing performances for aircraft icing mitigations. An array of DBD plasma actuators were designed and embedded on the surface of a NACA0012 airfoil/wing model in different layout configurations (i.e., different alignment directions of the plasm actuators (e.g., spanwise vs. streamwise), width of the exposed electrodes and the gap between the electrodes) for the experimental study. The experimental study was carried out in the Icing Research Tunnel available at Iowa State University (i.e., ISUIRT). While the dynamic anti-icing operation is recorded by using a high-resolution imaging system, a high-speed Infrared (IR) thermal imaging camera is used to quantitatively map the temperature distributions over the surface of the airfoil model during the anti-/deicing processes. Results show that, heat dissipation mechanism of the plasma actuator array in either streamwise and spanwise configurations differ one from another noticeably. Streamwise configuration shows non-uniformity downstream along the span of the airfoil/wing model. In the cases of the case with the plasma actuators in spanwise configurations, temperatures on the exposed electrodes are found to be higher than those of the case with the plasma actuators in streamwise configuration, due to convective heat transfer from the plasma actuation regions to the electrodes. It is also found that the optimum width of the plasma actuator’s exposed electrode is 4mm.
Kolbakir, Cem, Liu, Yang, Hu, Haiyang, Hu, Hui
A Parametric Study on the Thermodynamic Characteristics of DBD Plasma Actuation and Its Potential for Wind Turbine Icing Mitigation2019-01-20316/10/2019
Wind turbine icing represents the most significant threat to the integrity of wind turbines in cold weather. Ice formation on wind turbine blades was found to cause significant aerodynamic performance degradation, resulting in a substantial drop in energy production. Recently developed Dielectric barrier discharge (DBD) plasma-based anti-/de-icing systems showed very promising effects for aircraft icing mitigation. In this present study, DBD plasma-based anti-/de-icing systems were employed for wind turbine icing mitigation. First, a comprehensive parametric study is conducted to investigate the effects of various DBD plasma actuation parameters on its thermodynamic characteristics. An infrared (IR) thermal imaging system is used to quantitatively measure the temperature distributions over the test plate under various test conditions. DBD plasma actuators are embedded over the surface of a DU91-W2-250 wind turbine blade model, and a series of experiments were conducted by using the Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to evaluate the anti-/de-icing performance of the system for wind turbine icing mitigation. Dynamic anti-icing process was recorded by a high-speed imaging system, and an IR thermal camera was used to map the temperature distributions over the surface of the wind turbine blade model during the anti-/de-icing processes.
Kolbakir, Cem, Gao, Linyue, Liu, Yang, Hu, Hui
Summary of the High Ice Water Content (HIWC) RADAR Flight Campaigns2019-01-20276/10/2019
NASA and the FAA conducted two flight campaigns to quantify onboard weather radar measurements with in-situ measurements of high concentrations of ice crystals found in deep convective storms. The ultimate goal of this research was to improve the understanding of high ice water content (HIWC) and develop onboard weather radar processing techniques to detect regions of HIWC ahead of an aircraft to enable tactical avoidance of the potentially hazardous conditions. Both HIWC RADAR campaigns utilized the NASA DC-8 Airborne Science Laboratory equipped with a Honeywell RDR-4000 weather radar and in-situ microphysical instruments to characterize the ice crystal clouds. The purpose of this paper is to summarize how these campaigns were conducted and highlight key results. The first campaign was conducted in August 2015 with a base of operations in Ft. Lauderdale, Florida. Ten research flights were made into deep convective systems that included Mesoscale Convective Systems (MCS) near the Gulf of Mexico and Atlantic Ocean, and Tropical Storms Danny and Erika near the Caribbean Sea. The radar and in-situ measurements from these ten flights were analyzed and correlations defined. Key results included 1) derived relationships between radar reflectivity factor (RRF), Ice Water Content (IWC), and ice particle size distributions, 2) characterization of HIWC conditions at the -50°C and other flight levels, and 3) verification of pilot observations, such as low radar reflectivity factor and pitot and total air temperature (TAT) anomalies. This data set also enabled new pilot radar HIWC detection algorithms to be developed and tested. A second campaign was conducted in August 2018 to test proposed HIWC radar detection algorithms within a new set of storm systems. Seven research flights were conducted from bases of operations in Ft. Lauderdale, Florida; Palmdale, California; and Kona, Hawaii. Flights were made into convective systems over the Gulf of Mexico and into an eastern-Pacific tropical system that developed into Hurricane Lane. Using a new, NASA-developed radar processing technique called “Swerling”, regions of HIWC were identified, and estimates of IWC were produced, at distances up to 60 Nm ahead of the NASA DC-8. Subsequently, the DC-8 flew through these regions to acquire the in-situ measurements to verify the radar-based IWC estimates.
Ratvasky, Thomas, Harrah, Steven, Strapp, J. Walter, Lilie, Lyle, Proctor, Fred, Strickland, Justin, Hunt, Patricia, Bedka, Kristopher, Diskin, Glenn, Nowak, John B., Bui, T. P., Bansemer, Aaron, Dumont, Christopher
Extension of a 2D Algorithm for Catch Efficiency Calculation to Three Dimensions2019-01-20136/10/2019
Accurate calculation of the catch efficiency β is of paramount importance for any ice accretion calculation since β is the most important factor in determining the mass of ice accretion. A new scheme has been proposed recently in [1] for accurately calculating β on a discretized two-dimensional geometry based on the results of a Lagrangian droplet trajectory integrator (start and impact conditions). This paper proposes an extension to the algorithm in Ref. [1], which is applicable to three-dimensional surfaces with arbitrary surface discretization. The 3D algorithm maintains the positive attributes of the original 2D algorithm, namely mass conservation of the impinging water, capability to deal with overlapping impingement regions and with crossing trajectories, computational efficiency of the algorithm, and low number of trajectories required to reach good accuracy in catch efficiency. At the same time, the new 3D algorithm avoids typical difficulties of other approaches to determine the catch efficiency β, like noisy β (results varying significantly between neighboring surface cells), catch efficiency of zero for surface cells surrounded by other cells with β > 0, jagged impingement limits, catch efficiency β not available on the discretized surface but only on an intermediate plane, or interpolation problems of β between an intermediate plane and the actual discretized surface. The paper first reviews existing approaches in the literature to determine β, then describes in detail the extension of the algorithm in [1] to three dimensions and the steps taken to avoid the possible pitfalls in calculating β described above. The algorithm is then applied to two test problems, one being the wing/belly-fairing intersection of the Common Research Model (CRM) in clean configuration [2] and the other being a generic scoop intake. The paper closes with ideas for further development of the algorithm.
Bartels, Christian, Neubauer, Thomas, Hassler, Wolfgang
Wind Tunnel Measurements of Simulated Glaciated Cloud Conditions to Evaluate Newly Developed 2D Imaging Probes2019-01-19816/10/2019
Instrumentation that has been used for characterization of mixed-phase and glaciated conditions in the past, like the OAP probes, are subject to errors caused by variations in diffraction on the images away from the object plane and by the discrete nature of their particle detection and sizing. Correction methods are necessary to consider their measurements adequate for high ice water content (IWC) environments judged to represent a significant safety hazard to propellers and turbofan engine operability and performance. For this reason, within the frame of EU FP7 HAIC project, instrumentation characterization and validation is considered a major element need for successful execution of flight tests campaigns. Clearly, instrumentation must be sufficiently reliable to assess the reproducibility of artificial clouds with high ice water content generated in icing tunnels. Instruments are required to measure these conditions with a sufficient level of accuracy for the purposes of the testing. Currently, there is an anticipated basic uncertainty of a factor of 2-5 when measuring clouds in-situ. This may be worse for thunderstorm core regions, because of the poorly measured ice particle sizes below 100 μm when using legacy instruments. Measurements below 100 μm are especially difficult for ice particles. In order to mitigate this measurement limitation, an innovative approach for imaging droplets and ice crystals was considered in this work. This method is based on Artium Technologies Inc. High Speed Imaging (HSI) instrument. The method utilizes a unique multi-beam illumination approach to control the depth of field, minimize out-of-focus image noise effects, and limit obscuration of particles in the sample volume produced by out-of-focus particles in the optical path. Rather than utilizing a linear array to acquire the images, a modern CMOS two-dimensional array imaging system is used. The lasers used for producing bright field shadow images are pulsed synchronously and have pulse duration of as little as 12.5 ns to “freeze” the particle motion. The response of the HSI will be reviewed on the basis of comparison with SPEC 2D-S by means of wind tunnel measurements for glaciated cloud conditions.
Esposito, Biagio M., Bachalo, William D., Leroy, Delphine, Schwarzenboeck, Alfons, Jurkat, Tina, Voigt, Christiane, Bansmer, Stephan
An Explorative Study to Use Super-Hydrophilic/Super-Hydrophobic Hybrid Surfaces for Aircraft Icing Mitigation2019-01-19956/10/2019
An explorative study was performed to demonstrate the feasibility of using a novel hybrid anti-/de-icing strategy for aircraft icing mitigation. The hybrid method was developed by combining the electro-thermal heating mechanism and specialized surfaces/coatings with different wettabilities. While an electrical film heater was utilized to provide thermal energy around the leading edge of a NACA0012 airfoil model, two different coating strategies, (i.e., (a). Superhydrophobic coating covering the entire airfoil surface to increase droplets bounce-off and accelerate surface water runback vs. (b). super-hydrophilic coating at the leading edge to increase evaporation area + superhydrophobic coating in downstream to prevent runback refreezing) were proposed and evaluated aiming at maximizing the anti-/de-icing efficiency of the hybrid method. While a series of experiments were conducted to examine the dynamics of droplet impinging onto the different surfaces (i.e., superhydrophobic vs. super-hydrophilic), a comprehensive experimental study was carried out in the Icing Research Tunnel at Iowa State University (i.e., ISU-IRT) to evaluate the anti-/de-icing performance of the hybrid method with the different coating strategies. It was found that, while both of the coating strategies could promote better anti-/de-icing performance of the hybrid method in comparison to the conventional heating-only method at rime ice condition. For glazed ice condition, the use of superhydrophobic coating over the entire airfoil surface would result in a maximized anti-/de-icing efficiency of the hybrid method (i.e., achieve a complete ice prevention with only 3% chord length covered with the electrical film heater), attributing to the significant droplets bounce-off and accelerated surface water runback behaviors.
Hu, Haiyang, Hu, Hui, Liu, Yang
Experimental Aerodynamic Simulation of Glaze Ice Accretion on a Swept Wing2019-01-19876/10/2019
Aerodynamic assessment of icing effects on swept wings is an important component of a larger effort to improve three-dimensional icing simulation capabilities. An understanding of ice-shape geometric fidelity and Reynolds and Mach number effects on iced-wing aerodynamics is needed to guide the development and validation of ice-accretion simulation tools. To this end, wind-tunnel testing was carried out for 8.9% and 13.3% scale semispan wing models based upon the Common Research Model airplane configuration. Various levels of geometric fidelity of an artificial ice shape representing a realistic glaze-ice accretion on a swept wing were investigated. The highest fidelity artificial ice shape reproduced all of the three-dimensional features associated with the glaze ice accretion. The lowest fidelity artificial ice shapes were simple, spanwise-varying horn ice geometries intended to represent the maximum ice thickness on the wing upper surface. The results presented in this paper show that changes in Reynolds and Mach number have only a small effect on the iced-wing aerodynamics relative to the clean-wing configuration. Furthermore, the addition of grit roughness to some lower-fidelity artificial ice shapes resulted in favorable lift and pitching moment comparisons to the wing with the highest fidelity artificial ice shape. For the wing with simple horn ice shapes, the dependence of maximum lift coefficient on horn height and angle are generally consistent with the trends observed for similar experiments conducted on iced airfoils in past research. In terms of usable lift however, the horn height did have a significant effect even for lower horn angles. This could be an important finding since usable lift may be more indicative of the impending iced-swept wing stall and need for additional pitch control than maximum lift coefficient.
Broeren, Andy P., Potapczuk, Mark G., Lee, Sam, Woodard, Brian S., Bragg, Michael B., Smith, Timothy G.
An Experimental Study to Evaluate Hydro-/Ice-Phobic Coatings for Icing Mitigation over Rotating Aero-engine Fan Blades2019-01-19806/10/2019
Ice accretion on aero-engines, especially on the fan blades, is the very hazardous icing incident due to the potential performance degradation of jet-engines. In the present study, an experimental investigation was conducted to examine the performance of ice-phobic coatings for jet-engine fan icing mitigation. The experimental study was performed in the unique Icing Research Tunnel at Iowa State University (ISU-IRT) with a scaled engine fan model operated under wet glaze and dry rime ice conditions. To evaluate the effects of anti-icing coatings and to acquire the important details of ice accretion and shedding process on fan blade surfaces, a “phase-locked” imaging technique was applied with a high-resolution imaging system. The power input required to drive the engine fan model rotating at a constant prescribed speed was also measured during the ice accretion experiment. It was found that both super-hydrophobic surface (SHS) and ice-phobic coating have its advantage in engine anti-icing. SHS facilitated the blades surface with much less ice, under both glaze icing and rime icing conditions, while ice-phobic coating prevents the large ice chunk formed in the leading edge as the ice chunk easily shed from the leading edge, compared with SHS blade and blades with a hydrophilic coating. Meanwhile, ice accreted on fan blades was also found to result in the degradation of the engine performance as the required power input to drive the engine fan model increased significantly as the ice accreted on the fan blades. To fully investigate power consumption, all blades are painted with SHS. The test results show that all the blades surface are nearly ice-free and the power consumption remains at a lower level compared with the situation all blades without coating treatment.
Tian, Linchuan, Liu, Yang, Li, Linkai, Hu, Hui
A Study of Droplet Breakup in the Vicinity of an Airfoil2019-01-20006/10/2019
Supercooled large droplets can breakup before imping on aerodynamic surfaces and this should be taken into account in the icing codes. A study of droplets breakup in the vicinity of an airfoil has been conducted. Experiments for streams of droplets that were allowed to fall in the path of an incoming airfoil attached to a rotatory arm were conducted at the INTA facility. Droplets diameters ranged from 500 μm to 3 mm and two airfoils models of leading edge radius of 70 mm and 103 mm moving at velocities of 70 m/s, 80 m/s and 90 m/s were tested. Two subsets of experimental data for both bag and stamen breakup and shear breakup modes were used in this investigation. For these cases a numerical trajectory and deformation model was applied to obtain the evolution of the horizontal position, and the droplet maximum and minimum diameter. Breakup onset was determined from experimental data. Though previous works considered that breakup starts when there is a minimum in the minimum diameter, such minimum was not found in the integration of the model. However, it was found a minimum in the derivative of the minimum diameter at the breakup onset. The implication of this finding has been discussed. Additionally, the minimum in the derivative of the minimum diameter is compared to a previous empirical breakup criterion and the results of the comparison have been discussed.
Sor, Suthyvann, Garcia-Magariño, Adelaida, Velazquez, Angel
A Three-Layer Thermodynamic Model for Ice Crystal Accretion on Warm Surfaces: EMM-C2019-01-19636/10/2019
Ingestion of high altitude atmospheric ice particles can be hazardous to gas turbine engines in flight. Ice accretion may occur in the core compression system, leading to blockage of the core gas path, blade damage and/or flameout. Numerous engine powerloss events since 1990 have been attributed to this mechanism. An expansion in engine certification requirements to incorporate ice crystal conditions has spurred efforts to develop analytical models for phenomenon, as a method of demonstrating safe operation. A necessary component of a complete analytical icing model is a thermodynamic accretion model. Continuity and energy balances are performed using the local flow conditions and the mass fluxes of ice and water that are incident on a surface to predict the accretion growth rate. In this paper, a new thermodynamic model for ice crystal accretion is developed through adaptation of the Extended Messinger Model (EMM) from supercooled water conditions to mixed phase conditions (ice crystal and supercooled water). A novel three-layer accretion structure is proposed and the underlying equations described. The EMM improves upon the original model for airframe icing, the Messinger Model, by permitting a linear temperature gradient through the ice and water layers. This in turn allows prediction of the time over which water exists in isolation on an initially warm surface, before an ice layer forms. This is of particular interest to engine icing, as surfaces may initially be significantly above freezing temperature, before cooling on exposure to ice particles. The method is solved in a multi-step approach, where the overall exposure time is divided into discrete windows, and the calculation performed over each window. This allows the local flow conditions to be updated between windows, permitting the incorporation of a reducing flow enthalpy due to particle evaporation, as well as transient engine operation. Model results are then compared to experimental results. Comparisons are made to solutions generated using the standard Messinger Model.
Bucknell, Alexander, McGilvray, Matthew, Gillespie, David, Jones, Geoffrey, Collier, Benjamin
An Eulerian Approach with Mesh Adaptation for Highly Accurate 3D Droplet Dynamics Simulations2019-01-20126/10/2019
Two main approaches are available when studying droplet dynamics for in-flight icing simulations: the Lagrangian approach, in which each droplet trajectory is integrated until it impacts the vehicle under study or when it leaves it behind without impact, and the Eulerian approach, where the droplet dynamics is solved as a continuum. In both cases, the same momentum equations are solved. Each approach has its advantages. In 2D, the Lagrangian approach is easy to code and it is very efficient, particularly when used in combination with a panel method flow solver. However, it is a far less practical approach for 3D simulations, particularly on complex geometries, as it is not an easy task to accurately determine the droplet seeding region without a great number of droplet trajectories, dramatically increasing the computing cost. Converting the impact locations into a water collection distribution is also a complex task, since droplet trajectories in 3D can follow convoluted paths. One of the advantages of the Lagrangian approach is the crisp definition of the shadow zone as it is clearly defined by the first trajectory to graze the surface of the vehicle. The Eulerian approach is much simpler to use with complex geometries, solving the entire domain as a whole, using the same grid as for the airflow, and there is no need to seed trajectories. For this reason, it is the preferred approach in most 3D icing solvers. One of its disadvantages, however, is that discontinuities, such as shadow zone limits or impingement limits, are usually not very sharply defined, with smoothing due to numerical dissipation and the grid, optimized heuristically for the airflow calculation, not being sufficiently fine in regions of solution discontinuities in the droplet solution. This paper presents a refined approach in the use of Eulerian algorithms for icing simulations by introducing a mesh adaption process simultaneously based on the airflow solution and the droplet solution. The results show the great potential of this approach in capturing the solution discontinuities very sharply, significantly reducing the uncertainty in determining shadow zone heights and impingement limits.
Pueyo, Alberto, Ozcer, Isik, Baruzzi, Guido
Event-Driven Simulation of Particle-Particle and Particle-Surface Collisions in Ice Crystal Icing2019-01-20146/10/2019
This paper describes an event-driven simulation tool for predicting particle-particle and particle-surface interactions in ice crystal icing (ICI). A new accretion model which is much less empirical than existing models for predicting ICI accretion is also described. Unlike previous models, the new “gouge/bounce model” (GBM) differentiates between (erosion) losses resulting from particle bounce and those resulting from particle gouging. A bounce threshold based on the tangential Stokes number is used to calculate most of the bounce loss. The GBM also predicts ejecta velocities and directions, at least approximately, which is important because most of the mixed-phase mass flux impacting a surface actually bounces off or erodes existing material in ICI, thereby increasing the mass flux downstream. The event-driven simulation tool, denoted COLLIDE, has been applied to two test cases in which accretion growth appeared to be affected by TWC in a manner beyond that which would be expected from the accumulation parameters. An existing correlation-based accretion model (CBM), modified to predict erosion dependence on particle diameter, is also implemented and applied to the test cases. COLLIDE predicted the observed accretion dependence on TWC in a least a qualitative fashion for the majority of model/test case permutations, supporting the hypothesis that collisions between backscattered and incident particles reduces erosion and thereby increases sticking efficiency as observed in experiments with larger particles. The predictions suggest scattering of incident particles by impacts with ejecta is the dominant mechanism responsible for the flux interference effect, not particle size reduction due to particle-particle collisions.
Currie, Thomas Charles
Numerical Modelling of Primary and Secondary Effects of SLD Impingement2019-01-20026/10/2019
A CFD simulation methodology for the inclusion of the post-impact trajectories of splashing/bouncing Supercooled Large Droplets (SLDs) and film detachment is introduced and validated. Several scenarios are tested to demonstrate how different parameters affect the simulations. Including re-injecting droplet flows due to splashing/bouncing and film detachment has a significant effect on the accuracy of the validations shown in the article. Validation results demonstrate very good agreement with the experimental data. This approach is then applied to a full-scale twin-engine turboprop to compute water impingement on the wings and the empennage. Since the performance characteristics of twin-engine commercial turboprops are such that they operate most efficiently at flight levels where SLD encounters may occur, the goal of this article is to establish a 3D computational methodology to eventually enable a complete study of the impact of FAR 25 Appendix O on the IPS requirements for this class of airplanes. The Appendix O icing conditions used for the demonstration of the methodology are set for a turboprop in a typical holding pattern at 6,000 ft, 190 kts, and 5° angle of attack. The air static temperature is 268 K and the LWC is 0.3 g/m3. Freezing drizzle environments are considered for the MVD > 40-micron droplet distributions. The results for these flight conditions show that inclusion of the secondary impingement due to splashing/bouncing in the simulation accounts for an increased water catch by 4.12% on the wing inboard section and 7.61% on the vertical stabilizer.
Fouladi, Habibollah, Baruzzi, Guido S., Nilamdeen, Shezad, Ozcer, Isik
Global Temperature Mapping and Crystallization Analysis of Supercooled Water Droplet Freezing Using Luminescent Imaging Technique2019-01-20096/10/2019
A prominent environmental phenomenon that greatly affects many industries including automotive, aeronautics, energy transmission, etc. is icing. One mechanism by which this occurs and plagues our machines and infrastructures that are exposed to the atmosphere is the icing of supercooled water droplets on a surface - either by impact against a surface or spontaneous nucleation and crystallization of a droplet at rest. The process by which nucleation propagates during the liquid-to-solid phase change and the thermodynamic implications in regards to latent heat generation and transfer are not fully understood on the single droplet scale. An attempt to better resolve these unknowns in both spatial and temporal domains has been made here. Previous efforts have implemented a unique temperature sensing technique utilizing luminescent dyes. A thermally sensitive luminescent paint coated onto the surface of interest allows direct mapping of the heat transfer from the supercooled liquid droplet undergoing freezing to the surface. This technique also provides insight into the nucleation propagation speed along the droplet-substrate interface. This, in conjunction with a high-speed color camera and an intense ultraviolet light source are used to accurately resolve the thermal energy within the freezing droplet in both space and time. Synchronization of the thermal data of the droplet with the measurements of transverse heat transfer through the impact surface allow an estimation of heat generation and loss to the environment - key factors in current modelling and simulation efforts used by researchers and industry to predict ice accretion and to better mitigate it.
Patterson, Wesley Chad, Sakaue, Hirotaka
Measurement of Liquid Water Content for Supercooled Large Drop Conditions in the NRC’s Altitude Icing Wind Tunnel2019-01-20076/10/2019
As a result of new regulations pertaining to the airworthiness of aircraft exposed to in-flight icing conditions where maximum water drop size is greater than 100 microns (referred to as Supercooled Large Droplet (SLD) conditions), updates are required to the test facilities and simulations that will enable manufactures to certify their products under these new rules. While a number of facilities report achieving some of the conditions specified in the new regulations, questions remain as to the suitability of the instrumentation used to measure the Liquid Water Content (LWC) and drop size distributions of the SLD icing cloud. This study aims to provide baseline LWC data through ice accretion measurement techniques on a NACA 0012 airfoil and rotating cylinders of varying diameters. This forms part of a collaborative effort between the NRC, NASA Glenn and the Italian Aerospace Research Centre (CIRA), to examine the suitability of current instruments in accurately measuring LWC in clouds where SLD conditions are present. Calculation of LWC’s from leading edge airfoil ice thickness measurements on the NACA 0012 airfoil were within ±10% of the tunnel LWC setting over the full range of MVD’s tested (20μm to over 300μm). When using rotating cylinders of varying size to measure LWC, it was found that smaller diameter cylinders underestimated LWC of icing clouds containing larger drop diameters compared to the tunnel setting whereas LWC measurement from larger cylinders provided values within 10% of the tunnel setting across the range of MVD’s tested.
Orchard, David M., Clark, Catherine, Chevrette, Gislain
Motivation, Development and Verification of a Rapid 3D Lagrangian Impingement Code - Trajectory and Catch 3D+ (TAC3D+)2019-01-20116/10/2019
This paper details the motivation, development and validation of a rapid 3D Lagrangian impingement code, Trajectory and Catch 3D+ (TAC3D+). AeroTex’s motivation to develop a 3D Lagrangian method was primarily driven by the inherent mesh dependent dissipation effect found in their 3D Eulerian Water Catch code (EWC) [1]. Studies performed by AeroTex have shown that for geometries where there are aft impingement regions that are partly shadowed by a more forward impingement region, the level of water flux dissipation can be significant, particularly if the mesh is coarse and the impingement region is far aft. Examples of issues where this may be a particular issue would be impingement on a centerline aft mounted engine or the calculation of impingement on the wing root/belly fairing. The code has been developed around a modified version of the OpenFOAM Lagrangian solver. The analysis process consists of three main phases; a coarse droplet trajectory calculation to identify the region of interest, a refined trajectory calculation that is sufficiently fine to calculate local water collection and a surface water collection efficiency calculation including mass loss due to splash and bounce associated with large droplets where applicable. The code allows the user to utilize multiple cluster queues to spread the job across multiple compute nodes to deliver the solution rapidly. The TAC3D+ code has been verified against a selection of 2D and 3D cases including some incorporating splash and bounce effects. The code is undergoing further development to incorporate the physics associated with ice crystals and the re-impingement of splashed particles. In addition, AeroTex are exploring methods to make the code even more efficient by maximizing time steps, utilizing different integration schemes and potential for the use of GPUs.
Roberts, Ian
Numerical Demonstration of the Humidity Effect in Engine Icing2019-01-20156/10/2019
The importance of the variation of relative humidity across turbomachinery engine components for in-flight icing is shown by numerical analysis. A species transport equation for vapor has been added to the existing CFD methodology for the simulation of ice growth and water flow on engine components that are subject to ice crystal icing. This entire system couples several partial differential equations that consider heat and mass transfer between droplets, crystals and air, adding the cooling of the air due to particle evaporation to the icing simulation, increasing the accuracy of the evaporative heat fluxes on wetted walls. Three validation cases are presented for the new methodology: the first one compares with the numerical results of droplets traveling inside an icing tunnel with an existing evaporation model proposed by the National Research Council of Canada (NRC). The second one compares humidity and the reduction in the outflow total temperature to the experimental data from NASA Glenn Research Center’s Propulsion Systems Laboratory (PSL). The third case shows that the vapor model improves our icing validation of the crowned cylinder case compared to the NRC experimental data. For the simulation technology demonstration, turbofan icing scenarios with inflow relative humidity varying between 30 and 100% are simulated using a generic engine intake that includes the first stages of the compressor. The inclusion of vapor transport and local relative humidity provide important additional modeling functionalities and increased simulation accuracy.
Zhang, Yue, Ozcer, Isik, Nilamdeen, Shezad, Baruzzi, Guido S., Selvanayagam, Jeyatharsan
Analysis of Experimental Ice Accretion Data and Assessment of a Thermodynamic Model during Ice Crystal Icing2019-01-20166/10/2019
This paper analyzes ice crystal icing accretion data and evaluates a thermodynamic ice crystal icing model, which has been previously presented, to describe the possible mechanisms of icing within the core of a turbofan jet engine. The model functions between two distinct ice accretions based on a surface energy balance: freeze-dominated icing and melt-dominated icing. Freeze-dominated icing occurs when liquid water (from melted ice crystals) freezes and accretes on a surface along with the existing ice of the impinging water and ice mass. This freeze-dominated icing is characterized as having strong adhesion to the surface. The amount of ice accretion is partially dictated by a freeze fraction, which is the fraction of impinging liquid water that freezes. Melt-dominated icing occurs as unmelted ice on a surface accumulates. This melt-dominated icing is characterized by weakly bonded surface adhesion. The amount of ice accumulation is partially dictated by a melt fraction, which is the fraction of impinging ice crystals that melts. Experimentally observed ice growth rates suggest that only a small fraction of the impinging ice remains on the surface, implying a mass loss mechanism such as splash, runback, bounce, or erosion. The fraction of mass loss must be determined in conjunction with the fraction of freezing liquid water or fraction of melting ice on an icing surface for a given ice growth rate. This mass loss parameter, however, along with the freeze fraction and melt fraction, are the only experimental parameters that are currently not measured directly. Using icing growth rates from ice crystal icing experiments, a methodology that has been previously proposed is used to determine these unknown parameters. This work takes ice accretion data from tests conducted by the National Aeronautics and Space Administration (NASA) at the Glenn Research Center in 2018 that examined the fundamental physics of ice crystal icing. This paper continues evaluation of the thermodynamic model from a previous effort, with additions to the model that account for sub-freezing temperatures that have been observed at the leading edge of the airfoil during icing. The predicted temperatures were generally in good agreement with measured temperatures. Other key findings include the total wet-bulb temperature being a good first order indicator of whether icing is freeze-dominated (sub-freezing values) or melt-dominated (above freezing). Maximum sticking efficiency values, the fraction of impinging mass that adheres to a surface, was calculated to be about 0.2, and retained this maximum value for a range of melt ratios (0.3 to 0.65 and possibly higher), which is defined as the ratio of liquid water content to total water content. Higher air velocities reduced the maximum sticking efficiency and shifted the icing regime to higher melt ratio values. Finally, the leading edge ice accretion angle was found to be related to ice growth (lower growth rates for smaller angles) and melt ratio (smaller melt ratios resulted in smaller angles, likely due to erosion effects).
Bartkus, Tadas P., Tsao, Jen-Ching, Struk, Peter M.
Ice Nucleation in the Presence of Electric Fields: An Experimental Study2019-01-20206/10/2019
In the present study, ice nucleation in sessile water drops during continuous cool down is studied experimentally under the impact of a constant electric field, to determine its influence on heterogeneous nucleation. The experimental setup enables simultaneous observation of multiple drops under well-defined conditions with and without an electric field and at temperatures down to -40 °C. A single experimental run contains 40 drops exposed to the same conditions. Drops with a well-defined size are produced employing a drop-on-demand drop generator. Based on multiple experimental runs using the same drops, the nucleation behavior is analyzed using statistical methods to determine the drop survival curves and nucleation site densities for varying conditions. Besides the influence of the electric field, the influence of different drop ensembles is investigated for a constant cooling rate of 5 K/min. A comparison of the experiments with and without an electric field is used to elaborate its influence on heterogeneous ice nucleation.
Löwe, Jens-Michael, Schremb, Markus, Hinrichsen, Volker, Tropea, Cameron
An Experimental Study on the Dynamic Ice Accretion Processes on Bridge Cables with Different Surface Modifications2019-01-20186/10/2019
An experimental study was conducted to investigate the dynamic ice accretion processes on bridge cables with different surface modifications (i.e., 1. Standard plain, 2. Pattern-indented surface, and 3. helical fillets). The icing experiments were performed in the unique Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT). In order to reveal the transient ice accretion processes and the associated aerodynamic loadings on the different cable models under the different icing conditions (i.e., rime vs. glaze), while a high-speed imaging system was used to capture the transient details of the surface water transport and ice accretion over the cable surfaces, a high-accuracy dual-transducer force measurement system was also utilized to measure the aerodynamic loadings acting on the ice accreting cable models. It was found that the addition of surface features (i.e., pattern-indented surface vs. helical fillets) could effectively influence the dynamic ice accretion process and the final ice structures. Based on the temporally-resolved measurements of the aerodynamic drag forces acting on the different cable models, it was found that while the ice accretion on the standard plain cable and the cable with helical fillets could induce lower drag forces, the ice formation on the pattern-indented cable could essentially increase aerodynamic drag force. The findings derived from this study is of great importance in elucidating the underlying icing physics on bridge cables for the development of innovative, effective anti-/de-icing strategies tailored specifically for bridge icing mitigation and protection in cold climates.
Liu, Yang, Peng, Yihua, Chen, Wenli, Hu, Hui
The Influence of SLD Drop Size Distributions on Ice Accretion in the NASA Icing Research Tunnel2019-01-20226/10/2019
An ice shape database has been created to document ice accretions on a 21-inch chord NACA0012 model and a 72-inch chord NACA 23012 airfoil model resulting from an exposure to a Supercooled Large Drop (SLD) icing cloud with a bimodal drop size distribution. The ice shapes created were documented with photographs, laser scanned surface measurements over a section of the model span, and measurement of the ice mass over the same section of each accretion. The icing conditions used in the test matrix were based upon previously used conditions on the same models but with an alternate approach to evaluation of drop distribution effects. Ice shapes resulting from the bimodal distribution as well as from equivalent monomodal drop size distributions were obtained and compared. Results indicate that the ice shapes resulting from the monomodal and bimodal drop size distributions had similar shapes, but the bimodal distributions had greater mass and volume measurements and icing limits that extended further back on the chord of the model.
Potapczuk, Mark G., Tsao, Jen-Ching
Quantification of 3D Ice Structures Accreted on a Wind Turbine Airfoil Model2019-01-20306/10/2019
Accurate quantification of 3D shapes of the complex ice structures accreted on wind turbine blades is highly desirable to develop ice prediction models for more accurate prediction of the aerodynamic performance degradation and power reduction due to the ice accretion on wind turbine blades. In the present study, an experimental investigation was conducted to quantitatively characterize the 3D shapes of the ice structures accreted over a DU91-W2-250 wind turbine airfoil model in the Icing Research Tunnel available at Iowa State University (ISU-IRT). A glaze icing condition and a rime icing condition that wind turbines usually experience in winter were duplicated by using ISU-IRT. A high-resolution non-intrusive 3D scanning system was used to make detailed 3D-shape measurements to quantify the complicated ice structures accreted on the wind turbine airfoil model as a function of the ice accretion time. The measurements results show that the complex 3D shapes of the ice structures accreted over the surfaces of the airfoil model under both glaze icing and rime icing conditions were well captured. It is found that the glaze ice accretion has stronger 3D features, in comparison to the rime ice accretion case, due to its wet nature. The measured 3D shapes of the complex ice structures at different ice accretion moments were also provided to demonstrate the progressive shape changes of the ice structures during the dynamic ice accretion process.
Gao, Linyue, Veerakumar, Ramsankar, Liu, Yang, Hu, Hui
Experimental Investigations of an Icing Protection System for UAVs2019-01-20386/10/2019
UAV icing is a severe challenge that has only recently shifted into the focus of research. Today, there are no mature icing mitigation technologies for UAVs, except for the largest fixed-wing drones. We are working on the development of an electro-thermal icing protection technology called D•ICE for medium-sized fixed-wing UAVs. As part of the design process, an experimental test campaign at the Cranfield icing wind tunnel has been conducted. This paper describes the icing protection system and shares experimental results on its capability for icing detection and anti-icing. Icing detection is based on an algorithm evaluating temperature signals that are induced on the leading-edge of the wing. A baseline signal is generated during dry (icing cloud off) conditions and compared to a signal during wet (icing cloud on) conditions. Due to significant differences in the heat transfer regime, the system can differentiate between these two states. The experiments show that our system can reliably detect icing conditions based on this principle. Furthermore, the anti-icing capability of the system is proven for two icing cases. The minimal required heat flux to keep the surface ice-free was obtained by gradually reducing power supply to the heating zones until icing could be detected. These experimental results were compared to FENSAP-ICE simulations. The test campaign includes a successful fully-autonomous run, where the system automatically detected icing and initiated suitable anti-icing measures.
Hann, Richard, Borup, Kasper, Zolich, Artur, Sorensen, Kim, Vestad, Håvard, Steinert, Martin, Johansen, Tor
The Effect of Crosswinds on Icing at Turbofan Engine Inlet2019-01-20246/10/2019
Ice accretion at engine inlet has a dangerous effect on the inlet airflow and shed ice would be ingested into the engine and cause compressor blades damage, and even combustors flame out. In order to analyze the effect of crosswinds on icing at turbofan engine inlet, a complete icing analysis method, which is based on the Messinger model and takes the influence of runback water into consideration, is constructed. The runback water is considered laminar flow and the flow direction is dominated by the bottom flow of air. The supercooled water droplets impingement, ice accretion and runback water characteristics and inlet distortion with and without ice were investigated at crosswinds speed of 15, 20, 25, 30 kt. The variation of local water collection coefficient β is unchanged at crosswind conditions, but the location of the maximum value and non-dimensional impact limits change with the crosswind, which move backward along the outer edge on the windward, and move along the inner edge on the leeward. The ice thickness on windward surface increases slightly near the stagnation point, and the outer icing limit occurs at more rear position with crosswinds. On leeward surface, the variation is opposite to the windward and the ice shapes present a more symmetrical distribution at stagnation point. On the smooth inlet surface, the inlet airflow at the fan is relatively uniform, and the total pressure ratio variation at the inlet lip also is regular as crosswind increases. Greatly losses of airflow occur after ice accretion at crosswind conditions, which cause uneven inlet airflow. The effect of the crosswind on ice accretion at the inlet should be considered when designing and optimizing anti-icing system. Otherwise, the ice formation under crosswind will deteriorate the inlet airflow quality and pose a hazard to aircraft safety.
Yang, Qian, Guo, Zhiqiang, Zheng, Mei, Dong, Wei
A Novel Heating-Coating Hybrid Strategy for Wind Turbine Icing Mitigation2019-01-20296/10/2019
The electro-thermal method is most commonly used for wind turbine anti-/de-icing. The upmost drawback of such systems is the high power consumption. In the present study, we proposed to use a durable slippery liquid-infused porous surface (SLIPS) to effectively reduce the power requirement of the heating element during the anti-/de-icing process. The explorative study was conducted in the Icing Research Tunnel at Iowa State University (ISU-IRT) with a DU91-W2-250 wind turbine blade model exposed under severe icing conditions. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion process, an infrared (IR) thermal imaging system was also utilized to achieve the simultaneous surface temperature measurements over the test model. In comparison to the traditional electrical heating strategies to brutally heat massive area of entire turbine blades, a novel heating-coating hybrid strategy, i.e., combining a leading-edge (LE) heating element to cover the first 30% of the chord length (C) along with using SLIPS to coat entire blade surface, was found to be able to keep the entire blade surface completely free of ice, but with only an approximately 30% of the required energy consumption. The readily bouncing of the water droplets upon impinging onto the durable SLIPS and the much lower ice adhesion strength/capillary force over the SLIPS coated surface are believed to be the reasons to lead the better anti-/de-icing performance of the heating-coating hybrid strategy to prevent ice accretion/formation over the surfaces of the wind turbine blades.
Gao, Linyue, Ma, Liqun, Liu, Yang, Hu, Hui
An Experimental Study on a Hot-Air-Based Anti-/De-Icing System for the Icing Protection of Aero-Engine Inlet Guide Vanes2019-01-20396/10/2019
In the present study, an experimental investigation was conducted to characterize a hot-air-based anti-/de-icing system for the icing protection of aero-engine inlet guide vanes(IGVs). The experimental study was conducted in a unique icing research tunnel available at Iowa State University (i.e., ISU-IRT). A hollowed IGV model embedded with U-shaped hot-air flowing conduit was designed and manufactured for the experimental investigations. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion or anti-/de-icing process over the surface of the IGV model for the test cases without and with the hot-air supply system being turned on, the corresponding surface temperature distributions on the IGV model were measured quantitatively by using a row of embedded thermocouples. In addition to investigating the characteristics of the convective heat transfer over the surface of the heated IGV model, a comprehensive parametric study was also conducted to evaluate the effects of the operation parameters of the hot-air-based anti-/de-icing system on its performance for IGV icing protection. The acquired ice accretion or anti-de-icing images were coordinated with the quantitative surface temperature measurements to elucidate the underlying physics. It was demonstrated clearly that, with proper operation parameters (i.e., by selecting proper heater temperature and mass flowrate of the hot-air stream), the hot-air-based anti-/de-icing system would be able to effectively prevent ice formation/accretion over the entire surface the IGV model.
Li, Linkai, Tian, Linchuan, Liu, Yang, Hu, Hui, Liu, Xuejun, Hogate, Isaac, Kohli, Atul
UAV Icing: Ice Accretion Experiments and Validation2019-01-20376/10/2019
Atmospheric icing is a key challenge to the operational envelope of medium-sized fixed-wing UAVs. Today, several numeric icing codes exist, that all have been developed for general aviation applications. UAVs with wingspans of several meters typically operate at Reynolds numbers an order of magnitude lower than commercial and military aircraft. Therefore, the question arises to what extent the existing codes can be applied for low-Reynolds UAV applications to predict ice accretion. This paper describes an experimental campaign at the Cranfield icing wind tunnel on a RG-15 and a NREL S826 airfoil at low velocities (25-40m/s). Three meteorological icing conditions have been selected to represent the main ice typologies: rime, glaze, and mixed ice. Each case has been run at least twice in order to assess the repeatability of the experiments. Manual ice shape tracings have been taken at three spanwise locations for each icing case. The liquid water content calibration was performed according to ARP5905 using the icing blade method. The tests have initially shown significantly higher water contents than anticipated, which could be traced to dimensional differences of the blade at Cranfield, as well as low flow velocities. This systematic error was resolved by simulating the droplet collection coefficients on the off-specification blade. In addition to manual tracings, photogrammetry and a handheld laser-scanner were used to capture the ice shapes. The results indicate that manual tracings are still the most efficient method, although there is potential in exploring the alternatives further. Additionally, numerical simulations with two icing codes, LEWICE and FENSAP-ICE, were performed on a rime and a glaze case. For rime, the simulations show a good agreement with the experiment, whereas the glaze case exhibits significant differences.
Hann, Richard
Predicted Ice Shape Formations on a Boundary Layer Ingesting Engine Inlet2019-01-20256/10/2019
Computational ice shapes were generated on the boundary layer ingesting engine nacelle of the D8 Double Bubble aircraft. The computations were generated using LEWICE3D, a well-known CFD icing post processor. A 50-bin global drop diameter discretization was used to capture the collection efficiency due to the direct impingement of water onto the engine nacelle. These discrete results were superposed in a weighted fashion to generate six drop size distributions that span the Appendix C and O regimes. Due to the presence of upstream geometries, i.e. the fuselage nose, the trajectories of the water drops are highly complex. Since the ice shapes are significantly correlated with the collection efficiency, the upstream fuselage nose has a significant impact on the ice accretion on the engine nacelle. These complex trajectories are caused by the ballistic nature of the particles and are thus exacerbated as particle size increases. Shadowzones are generated on the engine nacelle, and due to the curvature of the nose of the aircraft the shadowzone boundary moves from lower inboard to upper outboard as particle size increases. The largest particle impinging one the engine nacelle from the 50-bin discretization was the 47 μm drop diameter. As a result, the MVD greater than 40 μm Appendix O conditions were characterized by extremely low collection efficiency on the engine nacelle for these direct impingement simulations.
Porter, Christopher
Electromechanical Resonant Ice Protection Systems: How to Favour Fractures Propagation2019-01-20326/10/2019
Many researches focus on piezoelectric ice protection systems with the objectives to develop light and low consumption resonant electromechanical systems for de-icing. These systems use the vibrations generated by piezoelectric actuators at resonance frequencies to produce shear stress at the interface between the ice and the support or to produce tensile stress in the ice. This article presents experimental results of de-icing tests performed with resonant piezoelectric systems that generate amplitudes of vibrations to exceed ice tensile strength or ice/support adhesive shear strength. The tests show that fractures are initiated but that the ice is not always completely detached. A methodology based on the energy release rate is presented to enable a better understanding of fractures initiation and propagation. The last section part of the article is dedicated to the study of a substrate made of a sandwich structure with a honeycomb panel in order to maximize fractures propagation while minimizing energy consumption.
Rouset, Pierrick, Pommier-Budinger, Valérie, Budinger, Marc
Validation and Instrumentation of a Small Modular Multi-Stage Axial Compressor for Ice Crystal Icing Research2019-01-19406/10/2019
The National Research Council of Canada (NRC) has undergone the development of a Small Axial Compressor Rig for modelling altitude ice accretion in aircraft engines. The rig consists of two axial compressor stages measuring approximately 150mm in diameter, an extension duct to allow residence time for partial melting of ice crystals and a test piece. The axial compressor stages are intended to provide realistic engine conditioning such as fracture, pressure rise, temperature rise and centrifuging of glaciated ice crystals entering the rig. The rig was designed for use in altitude icing wind tunnels such as the NRC’s altitude icing wind tunnel (AIWT), research altitude test facility (RATFac.), and those of other organization such as NASA Glenn and Technical University of Braunshweig. Previous development work [1] provided partial validation of the aerodynamic performance of just the first compressor stage at 90% power. Recent development work has concluded the aerodynamic validation of both the first and the second stages and performance was found to be satisfactory for purpose. A prediction of the ice accretion behavior of the rig based on validated performance is provided. Details of the instrumentation scheme including measurement technique for the radial distribution of ice crystal downstream of the compressor stages, and measurement of particle sizes before and after each stage are also presented.
Neuteboom, Martin, Chalmers, Jennifer, Currie, Thomas
Icing Test and Measurement Capabilities of the NRC’s Gas Turbine Laboratory2019-01-19436/10/2019
The National Research Council’s Gas Turbine Laboratory provides industry leading icing facilities that allow manufacturers to develop, validate and certify new products for flight in adverse conditions. This paper shows how NRC measurement techniques are used across the facilities, and presents a literature-review of recently developed capabilities. The overview includes new details on some facilities, and future capabilities that are in development or planned for the near future. Methods developed at the NRC for characterizing inclement conditions are discussed and include the Isokinetic Probe, Particle Shadow Velocimetry, the Particle Detection Probe, and a size-binned real-time thermodynamic evaporation model. These are used to deliver accurate icing water content in facilities like the sea-level ice crystal generator, the Rotating Icing Rig, the Research Altitude Testing Facility, and liquid water test facilities in Ottawa and in Thompson, Manitoba at the Global Aerospace Centre for Icing and Environmental Research (GLACIER).
Chalmers, Jennifer, Davison, Craig, MacLeod, James, Neuteboom, Martin, Fuleki, Dan
Items per page:
1 – 50 of 290