The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Julie J E Teuwen - One of the best experts on this subject based on the ideXlab platform.
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a computational framework for coating fatigue analysis of wind turbine blades due to Rain Erosion
Renewable Energy, 2021Co-Authors: Weiyi Chen, Xiaobo Wang, Zhiyu Jiang, Yeqing Wang, Amrit Shankar Verma, Julie J E TeuwenAbstract:Abstract The Rain-induced fatigue damage in the wind turbine blade coating has attracted increasing attention owing to significant repair and maintenance costs. The present paper develops an improved computational framework for analyzing the wind turbine blade coating fatigue induced by Rain Erosion. The paper first presents an extended stochastic Rain field simulation model that considers different Raindrop shapes (spherical, flat, and spindle), Raindrop sizes, impact angles, and impact speeds. The influence of these Raindrop characteristics on the impact stress of the blade coating is investigated by a smoothed particle hydrodynamics approach. To address the expensive computational time, a stress interpolation method is proposed to calculate the impact stress of all Raindrops in a random Rain event. Furthermore, coating fatigue analysis is performed by including the fatigue crack initiation in the incubation period and the fatigue crack propagation in the mass-loss-rate increasing period due to Raindrop impact. Finally, the proposed computational framework is verified by comparing the estimated fatigue life with those obtained in literature. The results from the study show that by incorporating the statistics of Rainfall data, the proposed framework could be used to calculate the expected fatigue life of the blade coating due to Rain Erosion.
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methodology for the energetic characterisation of Rain Erosion on wind turbine blades using meteorological data a case study for the netherlands
Wind Energy, 2021Co-Authors: Luis Bartolome, Julie J E TeuwenAbstract:Rain Erosion on the leading edge of wind turbine blades is an intricate engineering challenge for the wind industry. Based on an energetic approach, this work proposes a methodology to characterise the Erosion capacity of the Raindrop impacts onto the leading edge blades. This methodology can be used with meteorological data from public institutions or from direct measurements at the wind turbine locations. The Erosion characterisation is analysed using accumulative and per impact erosive variables, that is, total kinetic energy and kinetic energy per impact. To consider the frequency of impacts, two erosive variables are proposed, namely, total kinetic power and kinetic power per impact. These variables are calculated using the data from the Royal Netherlands Meteorological Institute (Koninklijk Nederlands Meteorologisch Instituut, KNMI) of the last 25 years jointly with the operation specifications of an actual wind turbine model (Suzlon S111). The main contribution to the erosive variables was found to be the wind speed because it controls the rotational velocity of the wind turbine. Also, the intensity of the Rainfall and the frequency of meteorological data logging, that is, the temporal resolution of data, play a significant role.
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prospective challenges in the experimentation of the Rain Erosion on the leading edge of wind turbine blades
Wind Energy, 2019Co-Authors: Luis Bartolome, Julie J E TeuwenAbstract:Developments in the wind industry reveal intricate engineering challenges, one of them being the Erosion on the leading edge of the wind turbine blades. In this review work, the main issues for the wind industry in the experimentation with respect to Erosion are examined. After a historical and general overview of Erosion, this review focuses on the Rain Erosion on the leading edge of the wind turbine blades giving prominence to (1) the Rain simulations, (2) experimental Erosion facilities, and (3) variables to characterise Erosion. These three factors have to be improved to establish a research field enabling the prediction of Erosion behaviour and providing useful information about how the Rainfall affects the leading edge of the wind turbine blades. Moreover, these improvements in the experimentation of the Erosion would be a first step to understand and predict the Erosion damage of the wind turbine blades. Finally, this review work also will help to cope with experimental investigations and results in the Rain Erosion on the leading edge with a deeper critical thinking for future researchers.
T M Young - One of the best experts on this subject based on the ideXlab platform.
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correlation of the Rain Erosion performance of polymers to mechanical and surface properties measured using nanoindentation
Wear, 2018Co-Authors: A Ocarroll, Mark Hardiman, E F Tobin, T M YoungAbstract:Abstract Rain Erosion of leading edges of wind turbine blades is caused by repeated high speed liquid droplet impacts, which causes damage in the form of pitting or peeling over time and can lead to a significant reduction in performance if left untreated. Due to an increase in the tip speed of modern wind turbine blades, Rain Erosion is becoming an increasingly prominent issue. Currently, polymeric coatings are applied to the surface of the wind turbine during manufacture in order to mitigate the issue; however, it has been reported that these coatings are being eroded within the first 2–5 years of the 15–25 year life cycle of the blades. Rain Erosion testing of polymer coatings requires prolonged characterisation using expensive bespoke apparatus. The focus of this study is to assess if nanoindentation can conveniently provide sufficient information to characterise the Rain Erosion resistance of polymeric materials. A range of polymeric materials were first tested in the Whirling Arm Rain Erosion Rig (WARER) to assess their ability to resist Rain Erosion, while a Nanoindenter G200 was also used to assess their stiffness, hardness, surface roughness, elastic and viscoelastic properties. The results indicated a number of correlations. A reduction in both storage modulus and hardness was seen to be beneficial for Rain Erosion resistance and materials that resist Rain Erosion can recover quickly to their original shape in time to resist subsequent impacts. Viscoelasticity was assessed through the fitting of a spring and dashpot model to the nanoindentation data, showing good correlation. This technique also has the potential to experimentally characterise the viscoelastic properties required to create analytical or numerical models to evaluate Rain Erosion performance. Scanning probe microscopy carried out at various stages of the Erosion process showed that the roughness of the polymeric materials increases with Erosion time up to critical roughness (SaCRIT), before which no significant mass loss will occur. Furthermore, it was found that the rate at which a polymer is roughened during the incubation period is related to the rate at which it loses mass in the mass loss period, providing an empirical insight into the mechanics of the Rain Erosion of these materials.
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on the material characterisation of wind turbine blade coatings the effect of interphase coating laminate adhesion on Rain Erosion performance
Materials, 2017Co-Authors: Enrique Cortes, F Sanchez, Anthony Ocarroll, Orja Madramany, Mark Hardima, T M YoungAbstract:Rain Erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade Erosion, all wind turbine Original Equipment Manufacturers (OEMs) are actively seeking solutions. In most cases, since the surface coating plays a decisive role in the blade manufacture and overall performance, it has been identified as an area where a solution may be obtained. In this research, two main coating technologies have been considered: In-mould coatings (Gel coating) applied during moulding on the entire blade surface and the post-mould coatings specifically developed for Leading Edge Protection (LEP). The coating adhesion and Erosion is affected by the shock waves created by the collapsing water droplets on impact. The stress waves are reflected and transmitted to the laminate substrate, so microstructural discontinuities in coating layers and interfaces play a key role on its degradation and may accelerate Erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations based on their potential stress reduction on the interface. Nevertheless, in order to use them, it is necessary to measure the contact adhesion resistance of the multi-layered system interfaces. The Rain Erosion performance is assessed using an accelerated testing technique, whereby the test material is repeatedly impacted at high speed with water droplets in a Whirling Arm Rain Erosion Rig (WARER). The materials, specifically the coating–laminate interphase region and acoustic properties, are further characterised by several laboratory tests, including Differential Scanning Calorimetry (DSC), pull-off testing, peeling–adhesion testing and nanoindentation testing. This body of work includes a number of case studies. The first case study compares two of the main coating technologies used in industry (i.e., gel coating and LEP); the second case investigates the effects of the in-mould gel coating curing; and the third considers the inclusion of a primer layer on a LEP configuration system. Following these case studies, the LEP is found to be a far superior coating due to its appropriate mechanical and acoustic properties and the interface between the coating and the substrate is highlighted as a key aspect, as poor adhesion can lead to delamination and, ultimately, premature failure of the coating.
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comparison of liquid impingement results from whirling arm and water jet Rain Erosion test facilities
Wear, 2011Co-Authors: E F Tobin, T M Young, Dominik Raps, O RohrAbstract:Abstract A laboratory-scale Whirling Arm Rain Erosion test Rig (WARER) has been designed, developed and commissioned at the University of Limerick. The facility is capable of impact speeds of 178 ms−1 and a Rainfall rate of 25.4 mm h−1. Circular samples of 27 mm diameter (nominal) and a maximum thickness of 2 mm can be accommodated. The facility was developed to test the resistance of leading edge aircraft materials to the repeated impact of Rain droplets in flight. A challenging feature of the design was to enclose the whirling arm within a chamber so that it could be operated in an open-plan laboratory. A design problem that arose was the effect of aerodynamic heating of the air within the chamber. This led to a warming of the water and consequently a change in the droplet formation, which in turn caused problems relating to the repeatability of the tests. A cooling system was thus incorporated to keep the temperature of the water droplets below the established threshold of 20 °C. Calibration testing has been undertaken by conducting back-on-back testing of samples with a previously developed water-jet facility at EADS IW, Munich. This Pulsating Jet Erosion Test rig (PJET) is capable of 225 ms−1 droplet speed. Multiple impacts are produced on the sample at numerous locations, each location having an increased number of impacts. The impact frequency is equivalent of 25 mm h−1 Rain fall. Clad aluminium alloy (AA2024-T3) was used with the soft AA1230 clad layer being removed during testing. Post impact evaluations were carried out using Confocal Laser Scanning Microscopy (CLSM) and surface roughness measurements. A cumulative Erosion-time curve was produced from the WARER samples.
Soren Kiil - One of the best experts on this subject based on the ideXlab platform.
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Rain Erosion of wind turbine blade coatings using discrete water jets effects of water cushioning substrate geometry impact distance and coating properties
Wear, 2015Co-Authors: Shizhong Zhang, Kim Damjohansen, Pablo L Bernad, Soren KiilAbstract:Abstract Rapid and reliable Rain Erosion screening of blade coatings for wind turbines is a strong need in the coatings industry. One possibility in this direction is the use of discrete water jets, where so-called jet slugs are impacted on a coating surface. Previous investigations have mapped the influence of water jet slug velocity and impact frequency. In the present work, the effects on coating Erosion of water cushioning, substrate curvature, and water nozzle-coating distance were explored. The investigations showed that in some cases water cushioning (the presence of a liquid film on the coating surface prior to impact) influences the Erosion. Contrary to this, substrate curvature and the water nozzle-coating distance ( Mechanical measurements to characterize selected blade coatings, including tensile strength, flexibility, impact, hardness, and abrasion experiments, were also conducted. The ranking of abrasion resistance of the blade coatings was in agreement with the ranking of Rain Erosion resistance measured in the whirling arm rig (an industrial standard). Results of this work, with more pertinent parameters explored, confirm the conclusion from the previous investigation that a direct correlation of data from discrete water jet experiments with those obtained in the whirling arm rig does not seem possible (at least not for the blade coatings considered). The underlying mechanisms of Rain Erosion are substantially different in a setup based on impacting water jet slugs and a setup where a rotor arm impacts falling water drops.
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Erosion of wind turbine blade coatings design and analysis of jet based laboratory equipment for performance evaluation
Progress in Organic Coatings, 2015Co-Authors: Shizhong Zhang, Kim Damjohansen, Pablo L Bernad, Sten Norkjaer, Soren KiilAbstract:Abstract Driven by the growth of the wind power industry during the last decade, the size of wind turbines has grown considerably and single-turbine power can nowadays reach a capacity of 8 MW with rotor diameters exciding 160 m. Rain Erosion is a considerable threat to the mechanical integrity of the blades in such equipment. To reduce expensive blade maintenance repairs and to avoid out-of-service periods, energy-absorbing blade coatings are required to protect rotor blades from Rain Erosion. In this work we describe the design, construction and evaluation of a laboratory setup for fast screening of up to 22 coating samples that is based on water jet slugs. Our objective is to study the effect of the parameters involved in the Rain Erosion process and to correlate our experimental results with data obtained with the complex and expensive whirling arm rig, which has become the industry standard method of test for Rain Erosion. Our results showed that water slug velocity and impact frequency are the most influential parameters in the coating Erosion rate. Coating defects, often present on the specimens tested, appeared to play an important role in the Erosion mechanism. Two particular experimental blade coatings were investigated using the proposed experimental design. The evaluation of the coatings under conditions where impact frequency and water hammer pressure were “matched” could not be directly correlated with the results obtained with the whirling arm rig. This result may be attributed, among other contributing factors, to the different contact modes in the two setups, i.e. the movement of coated panels against Rain drops versus the movement of water drops against coated specimens. Additional factors that require further investigation are the specimen geometries and the potential significance of the presence of a thin water film on the coated surfaces. Our results endorse the complex nature of the Rain Erosion phenomenon, which is the result of the simultaneous combination of complex mechanisms and as such, it is difficult to reproduce at the laboratory scale.
J E Field - One of the best experts on this subject based on the ideXlab platform.
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cavitation in impacted drops and jets and the effect on Erosion damage thresholds
Wear, 2012Co-Authors: J E Field, J J Camus, Marc Tinguely, Danail Obreschkow, Mohamed FarhatAbstract:It is well known that metals and alloys erode at lower impact threshold velocities than expected. This was studied by Thomas and Brunton (1970) who reported “discrepancy factors” in the range 4–10. These authors suggested that liquid impact was a more searching impact than solid impact since it was able to exploit weaknesses in the metal. Further, as Erosion develops the sideways liquid flow can add shear stresses to surface steps and hydraulically load liquid trapped in cracks and crevices. In 1970, Brunton and Camus showed that during the impact process cavities could form inside the liquid drops, and that some collapsed onto the solid surface. This provided a second potential mechanism to explain the low damage threshold with the cavity collapse adding to the “water hammer” pressures. However, Brunton and Camus were cautious in offering this as a potential mechanism. In this paper, we argue that the Brunton and Camus experiments were in a relatively low velocity regime (20–70 m s−1), compared with those in turbine Erosion and Rain Erosion of aircraft components. This paper presents high-speed photographic sequences of cavity formation and shock propagation in impacted liquids using a range of techniques. Finally, a new method is described in which a metal projectile is fired at a liquid jet. This produces large amounts of cavitation. Our conclusion is that the cavity collapse process can explain the observed lower threshold velocities
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high speed photography and stress gauge studies of jet impact upon surfaces
Philosophical transactions - Royal Society. Mathematical physical and engineering sciences, 1997Co-Authors: N K Bourne, Tetsuro Obara, J E FieldAbstract:Experiments were conducted to investigate the mechanisms of damage to brittle materials by liquidjet impact as seen in cavitation or simulated Rain Erosion. In this work, a liquidjet of 3 mm in dia...
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Rain Erosion resistance of diamond and other window materials
SPIE's 1994 International Symposium on Optics Imaging and Instrumentation, 1994Co-Authors: Colin R Seward, C S J Pickles, E J Coad, J E FieldAbstract:The multiple impact jet apparatus (MIJA) has generated a large amount of data on the damage inflicted on a material by high velocity liquid impact. The results presented in this paper include data on several protective coating systems, together with results from a study on the Rain Erosion resistance of natural and artificial diamond. Damage mechanisms resulting from liquid impact have been investigated by both high speed photography, and a video system for monitoring the extent of multiple impact damage. The results of these investigations also are discussed.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Rain Erosion data on window and dome materials
Window and Dome Technologies and Materials III, 1992Co-Authors: Colin R Seward, C S J Pickles, R Marrah, J E FieldAbstract:The development of diamond coatings has opened up new possibilities in the field of dome technology. The Cavendish Laboratory has long been involved in liquid impact studies of candidate window materials using a jet technique. This technique has been incorporated into a computer controlled automated Multiple Impact Jet Apparatus which has now been used to characterize the Rain Erosion properties of a variety of window systems including diamond coated samples. The results presented here compare the threshold velocities of damage for the new materials with those for current windows.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
E Van Der Heide - One of the best experts on this subject based on the ideXlab platform.
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leading edge Erosion of coated wind turbine blades review of coating life models
Renewable Energy, 2015Co-Authors: Henk Slot, E R M Gelinck, C Rentrop, E Van Der HeideAbstract:Erosion of the leading edge of wind turbine blades by droplet impingement wear, reduces blade aerodynamic efficiency and power output. Eventually, it compromises the integrity of blade surfaces. Elastomeric coatings are currently used for Erosion resistance, yet the life of such coatings cannot be predicted accurately. This review paper gives an overview of experimentally validated Erosion model blocks that can be used to predict the life of the leading edge of coated wind turbine blades. From the reviewed work it is concluded that surface fatigue, as nucleating wear mechanism for Erosion damage, can explain erosive wear and failure of the coatings. An engineering approach to surface fatigue, using the Palmgren–Miner rule for cumulative damage, allows for the construction of a Rain Erosion incubation period equation. Coating life was described as a function of the Rain intensity, the droplet diameter, the fatigue properties of the coating and the severity of the conditions. It is recommended to focus coating development on reduction of the impact pressure, e.g. by developing surfaces with a low modulus of elasticity; or on enlarging the safe area by: developing coatings with adjustable compressive stresses and hardness, or coatings without defects and impurities.
