ADAF Research Articles

Метрологические аспекты предполётных процедур противообледенительной обработки гражданских воздушных судов (окончание)

Snow-ice deposits formed on the outer surfaces of aircrafts on the ground during parking can have a negative impact during take-off due to the deterioration of aerodynamic and flight performance, a significant and even critical decrease in lift, increased drag, blocking controls, difficulty or blocking of landing gear retraction, damage to the blades of inlet guide vanes and/or the blades of an engine compressor. To exclude the influence of snow and ice deposits, anti-icing treatment is performed, including their removal and/or protection from subsequent formation. For this purpose, special anti-icing machines (deicers), equipped with such means of instrumental control as counters of anti-icing fluid pumps, measuring scales of anti-icing fluid tanks, thermometers and pressure gauges for temperature and pressure measuring at the outlet of a spray nozzle, are used. The article deals with the metrological aspects of civil aircrafts anti-icing prior to flight.

Study on the Freezing and Thawing Damage of Concrete Pavement under the Action of Deicing Agent

In the winter, large-scale passenger airports in northern China, aircraft deicing is a common job. This is because in the rainy and snowy weather in winter, the surface of the aircraft will freeze, and the aircraft is strictly forbidden to take off in the icing state. Therefore, there is a special de-icing platform in the airport to de-ice the aircraft. The deicing fluid containing chemical substances stays on the surface of the de-icing concrete, which will cause the concrete aggregate to peel off and crack, forming FOD and endangering flight safety. Therefore, this paper studied the properties of ethylene glycol deicing fluid and the freeze-thaw cycle damage test of concrete under the action of deicing fluid. The test results show that the low concentration deicing fluid has a greater damage to concrete freeze-thaw. In addition, the article uses finite element software to simulate the two-dimensional concrete frost heaving damage. The simulation results show that the damage propagation in the crack will be along the weak inner surface of the concrete, mainly along the concrete aggregate; under the same conditions, the influence of the depth of the crack on the concrete damage is greater than the impact of the crack width on the concrete damage.

Метрологические аспекты предполётных процедур противообледенительной обработки гражданских воздушных судов

Snow-ice deposits formed on the outer surfaces of aircrafts on the ground during parking can have a negative impact during
 take-off due to the deterioration of aerodynamic and flight performance, a significant and even critical decrease in lift, increased
 drag, blocking controls, difficulty or blocking of landing gear retraction, damage to the blades of inlet guide vanes and/or the
 blades of an engine compressor. To exclude the influence of snow and ice deposits, anti-icing treatment is performed, including
 their removal and/or protection from subsequent formation. For this purpose, special anti-icing machines (deicers), equipped with
 such means of instrumental control as counters of anti-icing fluid pumps, measuring scales of anti-icing fluid tanks, thermometers
 and pressure gauges for temperature and pressure measuring at the outlet of a spray nozzle, are used. The article deals with the
 metrological aspects of civil aircrafts anti-icing prior to flight.

Influence of Geometrical Parameters on Heat Transfer of Transversely Corrugated Helically Coiled Tube for Deicing Fluid

In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

Frostwing Co-Operation in Aircraft Icing Research

<div class="section abstract"><div class="htmlview paragraph">The aerodynamic effects of Cold Soaked Fuel Frost have become increasingly significant as airworthiness authorities have been asked to allow it during aircraft take-off. The Federal Aviation Administration and the Finnish Transport Safety Agency signed a Research Agreement in aircraft icing research in 2015 and started a research co-operation in frost formation studies, computational fluid dynamics for ground de/anti-icing fluids, and de/anti-icing fluids aerodynamic characteristics. The main effort has been so far on the formation and aerodynamic effects of CSFF. To investigate the effects, a generic high-lift common research wind tunnel model and DLR-F15 airfoil, representing the wing of a modern jet aircraft, was built including a wing tank cooling system. Real frost was generated on the wing in a wind tunnel test section and the frost thickness was measured with an Elcometer gauge. Frost surface geometry was measured with laser scanning and photogrammetry. The aerodynamic effect of the frost was studied in a simulated aircraft take-off sequence, in which the speed was accelerated to a typical rotation speed and the wing model was then rotated to an angle of attack used at initial climb. Time histories of the lift coefficient were measured with a force balance. The experiments showed that depending on the ambient temperature the frost may evaporate/melt during the take-off sequence. Lift losses after rotation with CSFF contamination at ambient temperatures of 4° to 7°C above freezing point were measured to be 4 to 5 % for roughness values, k/c, below 10<sup>-3</sup>. For comparison, lift loss tests with typical anti-icing fluids were performed resulting to roughly equal lift losses. This paper gives an overview of the performed activities.</div></div>

Electrolyte Effects on Poly (Acrylic Acid)-Based Aircraft De-icing Fluids

Poly (acrylic acid) [PAA]-based aircraft de-icing fluids are widely used commercially but are known to be subject to the formation of insoluble gel particles within wing structures. In this study, the rheological effects of the sodium chloride, potassium formate, and calcium acetate with commercially used PAA-based fluids are reported across the temperature range of −15 to 15 °C. Calcium ions have the potential to create gel particles, reflected in the shifts in the viscosity–temperature profile, while PAA aggregation is influenced by the concentrations and compositions of sodium and potassium salts in the water used for dilution. From the data presented, it is possible to create de-icing fluid formulations with the necessary rheological characteristics from stock solutions by dilution using available water sources, providing that the ion concentration is known.

Improving the efficiency of technological machines in the interaction with adhesive materials at negative temperatures

In this paper, the object of study is a technological machine that develops the cohesive ground. The MAXFLIGHT 04 anti-icing fluid is considered as a means of controlling the adhesion of the “soil-to-metal” system used in the operation of technological machines while developing moist cohesive soils under negative temperatures. The aim of the study is to increase the productivity and efficiency of technological machines in the developing wet cohesive soils at negative temperatures by reducing the soil-to-metal adhesion. Mathematical processing of the research results allowed us to obtain regression equations for two working conditions: a regression equation without using prophylactic agents to reduce soil adhesion and a regression equation using the MAXFLIGHT 04 anti-icing fluid. Using the obtained regression equations, the proportionality coefficient (the reduced friction coefficient f) was calculated. According to the calculation results, the values of the obtained proportionality coefficient depend on the shear plane of the temperature.

Multi-objective optimization of a new special-shaped tube for heating deicing fluid

The ground deicing heating system is an important equipment to ensure flight safety of civil aircraft in winter. As the main element, the heating tube directly affects the working efficiency of the system. The deicing fluid is high viscosity mixture. To improve heating efficiency of deicing fluid, a new special-shaped tube is proposed, which is named double-spiral trapezoidal grooved tube. The upper base width (m), groove depth (h) and base angle (θ) are the important structural parameters of the new tube. The optimal Latin hypercube design is applied to carry out the experiment design of m, h and θ. Nusselt number (Nu), flow resistance coefficient (f) and performance evaluation criteria (PEC) are selected as the optimization objectives. Then, the response surface approximation model is established to conduct sensitivity analysis. Based on the model, NCGA and NSGA-II algorithms are, respectively, introduced to perform the multi-objective optimization. The results show that NSGA-II is better than NCGA. When \(m \in \left[ {0.17, \, 0.33} \right]\), \(h \in [1.06, \, 1.08]\) and \(\theta \in \left[ {84.06, \, 84.75} \right]\), the best range of optimization objectives is \(Nu \in \left[ {86.04, \, 87.81} \right]\), \(f \in \left[ {0.70, \, 0.73} \right]\) and \({\text{PEC}} \in \left[ {1.60, \, 1.62} \right]\). With the growth of turbulence intensity, PEC > 1, and Nu increases by 4–27%. As a result, the heating efficiency of the new tube is superior to the original tube.

Treatment of de-icing contaminated surface water runoff along an airport runway using in-situ soil enriched with structural filter materials

Airport surface runoff during wintertime contains high concentrations of pavement de-icing fluids (PDFs). Uncontrolled discharge of this runoff poses a potential environmental hazard for the terrestrial and aquatic ecosystem. Several technologies for collection, transportation and treatment of contaminated runoff water are available, mainly technical systems, which require high operation and maintenance efforts. For moderately contaminated runoff, the discharge to a wastewater treatment plant is usually applied.In this study, a passive soil-based filter is proposed to treat the contaminated surface water runoff. The degradation of two PDFs was under investigation, namely Safeway® KA-Hot based on potassium acetate, and urea. The main research objective was to determine the capability of the in-situ soil and a soil based filter using zeolite and perlite as additional filter media to degrade the organic pollutants in the runoff. Column experiments at temperatures between 3 °C and 5 °C were carried out to determine the degradation potential when using 50% in-situ soil mixed with zeolite and perlite. Besides TOC, the nitrogen degradation was also under investigation. Due to the low temperatures, available nutrients are a key factor for the TOC degrading microorganisms. Overall TOC reduction rates were found from 76% up to 98%, with TOC effluent concentrations in the range of 18 to 870 mg·L−1, depending on the influent concentration. Based on the results, the use of a soil-based filter is a promising, passive, natural based solution for the treatment of de-icing runoff.

Development of the symmetrical laser shock test for weak bond inspection

This study aims to assess the capability of the LAser Shock Adhesion Test to detect weak bonds in assemblies made of carbon fibre reinforced polymer laminates as well as understand the behaviour of different bonded composite structure under a shock load. A specific setup based on symmetrical laser shocks has been used. After each test, ultrasounds are used to determine if the bond has been damaged or not. At first, samples with two contaminants - de-icing fluid and finger prints - were studied. Then, the bond quality of two partially contaminated aircraft parts were investigated. These original results demonstrate the efficiency of the symmetrical laser shocks method as a Non-Destructive Test for bonded carbon fibre reinforced polymer assemblies.

The NCAR–FAA Snow Machine: An Artificial Snow-Generation System

AbstractThe National Center for Atmospheric Research (NCAR) developed an artificial snow-generation system designed to operate in a laboratory cold chamber for testing aircraft anti-icing fluids under controlled conditions. Flakes of ice are produced by shaving an ice cylinder with a rotating carbide bit; the resulting artificial snow is dispersed by turbulent airflows and falls approximately 2.5 m to the bottom of the device. The resulting fine ice shavings mimic snow in size, distribution, fall velocity, density, and liquid water equivalent (LWE) snowfall rate. The LWE snowfall rate can be controlled using either a mass balance or a precipitation gauge, which measures the snowfall accumulation over time, from which the computer derives the LWE rate. LWE snowfall rates are calculated every 6 s, and the rate the ice cylinder is fed into the carbide bit is continually adjusted to ensure that the LWE snowfall rate matches a user-selected value. The system has been used to generate LWE snowfall rates ranging from 0 to 10 mm h−1 at temperatures from −2 to −30°C and densities of approximately 0.1–0.5 g cm−3. Comparisons of the snow-machine fluid tests with the outdoor fluid tests have shown that the snow machine can mimic natural outdoor rates under a broad range of conditions.

Thermal analysis of high viscosity deicing fluid in the heating system

Aircraft ground deicing is a crucial certification to civil flight safety in cold winter. Thermal analysis of high viscosity deicing fluid in Chinese ground heating system is carried out for promoting efficiency and flight punctuality. The structure of the system is asymmetrical, which is mainly composed of combustion chamber and heat exchange tube. Combustion releases energy to heat the deicing fluid in the exchange tube. Firstly, because of the formidable asymmetric structure, the grids of system need to be meshed separately to analyze the distribution of combustion temperature field. Secondly, due to the complex properties of deicing fluid, its main component ethylene glycol is selected as the working medium to examine the heat transfer performance. Then, the variation rules of thermo-physical parameters of ethylene glycol are compared with those of ideal fluid water. The results show that the asymmetric structure leads to the temperature field shifting to the gas outlet. The central area of the combustion chamber burns more fully than the edge area. Both dynamic viscosity coefficient and Prandtl number of ethylene glycol demonstrate similar nonlinear relationships when heating. Concerning thermal conductivity, Nusselt number and convection heat transfer coefficient, the variation rules of the two fluids are approximate, but the magnitudes of ethylene glycol are obviously less than those of water. Therefore, the high viscosity of fluid shows significant effect on heat transfer performance. Finally, a heating experiment is conducted to verify the reliability of the simulation. The research is beneficial to further explore the basic mechanism of combustion and heat transfer in the system, which is of great theoretical significance for optimizing and improving the existing Chinese deicing heating system.

Anti-Icing Fluid Secondary Wave and Its Role in Lift Loss During Takeoff

Effects of anti-icing fluid secondary wave on wing section lift degradation during simulated takeoff were studied in Aalto University Low Speed Wind Tunnel during 2012–2014 and 2016–2017. The existence of secondary waves has been frequently reported since the first studies of anti-icing fluid effects on the wing lift degradation. However, the studies on its quantitative contribution to the lift degradation are scarce. The effects of wing section geometry and configuration on the secondary wave have not been addressed in the previous studies. In the present study two different wind tunnel models were used: a DLR-F15 wing section with a chord of 0.65 m and a modified HL-CRM wing section with a chord of 0.63 m. Both were two-dimensional three-element models. The lift coefficient measurements suggested that the secondary wave may have a dominating contribution to the fluid-induced lift degradation. The slat size and geometry turned out to have a significant effect on the formation and size of the secondary wave.

Effect of Thermal Treatment on CFRP Parts Before and After Adhesive Bonding

Numerous non-destructive techniques are being investigated for assuring quality of the adhesive bonds. The research presented here is focused on non-destructive assessment of carbon fibre reinforced polymer (CFRP) parts. The surface condition directly influences the performance of adhesive bonds. The structural joints should ensure safe usage of a structure. However, some modifications of the surface may lead to weak bond that cannot carry the desired load. This is why there is a search for methods of surface assessment before bonding. Moreover, reliable techniques are required to allow to verify the integrity of the adhesive bond after manufacturing or bonded repair. We focus on the laser induced fluorescence (LIF) method for assessing the surface state. The LIF is a non-contact measurement method. In the context of adhesive bond assessment the electromechanical impedance (EMI) method is studied. The EMI uses surface bonded piezoelectric sensors for excitation and sensing. The investigated samples were made of CFRP layers. The samples were treated at elevated temperatures. The influence of the thermal treatment was studied using LIF. The thermal treatment at 220℃ could be clearly distinguishedrom the rest of the considered samples. The thermally treated plates were bonded to untreated plate and then they were measured with the EMI method to study the influence of the treatment on the adhesive bond. The changes of EMI spectra were significant for the treatment at 280℃ and for some thermally treated samples that were later contaminated with de-icing fluid.

Determination of adhesion strength of pre-bond contaminated composite-to-metal bonded joints by centrifuge tests

Abstract In the present work, the effect of pre-bond contamination scenarios related to production and repair processes on the adhesion strength of composite-to-metal joints is investigated by means of the novel centrifuge testing technology. The composite substrates have been subjected to contamination with release agent, moisture, fingerprint, thermal degradation and de-icing fluid before being bonded on the metallic stamp. Different contamination levels have been considered for each scenario. The standard deviation of adhesion strength values differs for each sample category and in some cases, is relatively high. The experimental results show a considerable decrease of adhesion strength for all contamination scenarios. The evaluation of the adhesion strength values is assisted by the characterization of the failure modes. In most cases, the transition between the failure modes explains the variation of adhesion strength. By taking into advantage the simplicity of the experimental process, numerous tests have been conducted within a very short time. Based on the practicality of the experimental process and the validity of the findings, it can be concluded that the centrifuge testing technology can be potentially used as a reliable testing method for the characterization of bonded joints.

Mechanical and Non-Destructive Study of CFRP Adhesive Bonds Subjected to Pre-Bond Thermal Treatment and De-Icing Fluid Contamination

Composite materials are commonly used in many branches of industry. One of the effective methods to join the carbon fibre reinforced polymer (CFRP) parts includes the use of adhesives. There is a search on effective methods for quality assurance of bonded parts. In the research here reported the influence of surface pre-bond modification on the adhesive bonds of CFRP plates has been analyzed. Adherends surface modifications, to include defects affecting the bonding quality, were obtained through surface thermal treatment, surface contamination with de-icing fluid and a combination of both the previously described treatments. Characterization of bonded joints was performed by means of mechanical testing, ultrasounds and electromechanical impedance (EMI) measurements. The study here proposed has also the aim to evaluate the ability of different destructive and non-destructive techniques to assess the quality of the bonds. While mechanical tests were strongly affected by the surface modifications, results obtained ultrasound and EMI test have demonstrate only a limited ability of these techniques to differentiate between the different samples. In fact, ultrasounds did not show any changes in the bondline, due to pre-bond modifications. However, this technique was able to detect delamination in CFRP for one of the samples thermally treated at 280 °C. Electromechanical impedance (EMI) measurements showed similar behavior as mechanical tests for samples thermally treated at 260 °C and 280 °C, and for the sample whose surface modification was made with a combination of thermally and de-icing fluid treatments.

Non-Wetting Nickel-Cerium Oxide Composite Coatings with Remarkable Wear Stability

ABSTRACTEngineered non-wetting surfaces inspired by biological species are of interest in the industry due to their potential applications such as water repelling, self-cleaning, anti-icing, anti-corrosion, anti-fouling, and low fluid drag surfaces. However, the adoption of non-wetting surfaces in large scale industrial applications has been hampered by synthesis techniques that are not easily scalable and the limited long term stability and wear robustness of these surfaces in service. In this study, we demonstrate a simple, low cost, and scalable electrochemical technique to produce robust composite coatings with tunable non-wetting properties. The composite coatings are composed of an ultra-fine grain nickel matrix with embedded hydrophobic cerium oxide ceramic particles. Comprehensive characterization, including wetting property measurements, electron microscopy, focused ion beam analysis, hardness measurements, and abrasive wear testing were performed to establish the structure-property relationships for these materials. The grain refinement of the nickel matrix contributes to the high hardness of the composites. As a result of the bimodal CeO2 particle size, hierarchical roughness is present on the surface of the composite, leading to remarkable non-wetting properties, even after 720 m of abrasive wear.

The persistence and photostabilizing characteristics of benzotriazole and 5-methyl-1H-benzotriazole reduce the photochemical behavior of common photosensitizers and organic compounds in aqueous environments.

Benzotriazole (BT) and 5-methyl-1H-benzotriazole (5-MeBT) are broadly used in industrial applications, such as anti-icing fluids and dishwashing detergent, and act as the primary building blocks for UV absorbers and photostabilizers. This study examined the occurrence of these two compounds in the environment and their unique photochemical behavior affecting photosensitizers and other micro-organic pollutants in aqueous environments. BT and 5-MeBT were detected in all river water samples from the major rivers in Taipei City in the concentration ranges of 147 to 1560ng/L and 22 to 235ng/L, respectively, and both compounds persisted through a conventional wastewater treatment plant. The direct photolysis half-lives of BT and 5-MeBT were 56.9 and 14.0h, respectively. The half-life of photolysis in river water for BT was 44.2h, whereas the half-life of 5-MeBT was 24.7h. The long half-lives in real-water matrices resulted in their prevalence in water bodies, and these compounds were also found to minimize the photosensitizing ability of nitrate and dissolved organic matter (DOM) and increase the persistence of other micro-organic pollutant. With BT present, the production of ·OH in nitrate photolysis was reduced, the degradation of DOM under sunlight was hindered, and the photodegradation of pharmaceutical residues in surface water, such as methotrexate, was completely impeded. This study suggests that in cases in which BT and 5-MeBT are highly concentrated, the effectiveness of natural attenuation process, i.e., photodegradation, in the aqueous environment is diminished, which increases the persistence of the pollutants as well as the risk of exposure.

Spectroscopic and chemiometrics supported studies on discrimination, phase transition and concentration identifications of 1,2-propylene glycol solutions, and of a mixture of potassium acetate with 1,3-propanediol solutions as anti-icing fluids

Aircrafts and runways de-icing operations with anti-icing fluids are still the most commonly used methods, in spite of their environmental impacts and associated costs. Once applied, these fluids are diluted because of adverse weather water inputs, conducting to a freezing point getting closer to 0°C. The characterization of their freezing points is therefore crucial. Four distinct anti-icing fluids, at concentrations ranging from their pure commercial form to an highly diluted rate were investigated by means of Raman spectroscopy and chemiometrics. The approach allowed the discrimination of the aircrafts anti-icing fluids between each other though containing the same active chemical compound, the rapid evolution towards 0°C of their freezing temperatures with the water dilution, and of the concentrations in active compounds of each fluid, along with their forecast.

Comparative evaluation of the anti-icing protection time of runway deicers using infrared thermography

This study presents a new method, based on infrared (IR) thermography, to evaluate and compare the anti-icing performance, i.e., the ability to delay the reformation of ice, of runways and taxiways deicing/anti-icing fluids (RDF) under icing precipitation. In summary, the test consists of applying on a standardized concrete pavement sample, a given quantity of a candidate de-icing fluid. Following the application, the concrete sample is submitted to low intensity freezing drizzle simulated in a cold chamber. Thermography picture is taken every 30s intervals until the concrete becomes completely iced. The measurement of anti-icing performance of different concentrations of propylene glycol (PG) and potassium-formate (KFOR) solutions are shown when assessed using the new IR method at −5°C, −8°C and −11°C.