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The wind turbine blades are exposed, during functioning, to the abrasive wear generated by the impact with air-borne sand particles. In this work, samples of a commercial wind turbine blade, made of a multi-layered composite material, are subjected to abrasive wear tests, using an air streamed wearing particles test rig. Following the analysis of the tests' results was found that the only protection against failure of the blade by abrasive damage is the surface layer. After its' penetration, the layers below are quickly destroyed, leading to the blade destruction. The investigation of the main abrasive wear influencing factors—particles' speed and acting time, showed that the particles' speed is the most important. To prove that an artificial neural network-based model was used. Also, a method for improvement of the blade resistance to abrasive wear is proposed, consisting of applying on the blade's surface of a polymeric foil. This offers supplementary protection of the surface layer, delaying its degradation. The tests performed on the protected samples prove the validity of the proposed method. Overall, the work showed the weakness of the blades' resistance in case of working in abrasive wear conditions and identified an improving method. [ABSTRACT FROM AUTHOR]

The lifecycle of wind turbine blades is around 20–25 years. This makes studies on the reuse of dismantled blades an urgent need for our generation; however, their recycling is very difficult due to the specific makeup of their composite material. In this study, the authors determined a concept for the reuse of turbine blade sections filled with concrete for geotechnical structures, retaining the walls, piles, or parts of their foundations. Working out detailed structural solutions to the above problem should be preceded by the identification of material parameters. In particular, getting to know the interface stress-strain characteristics is crucial. Therefore, this research focuses on the cooperation between recycled FRP composites and concrete in load-carrying, including experiments and numerical analyses. Regarding the two types of destructive stress, which may occur at the interface under both compression and bending, two types of tests were executed: the 'push-out test', modelling the interface's answer to shear stress, and the 'pull-off test', demonstrating the interface's reaction to normal stress. Additionally, the strength parameters of the materials used were tested. The numerical model for the push-out process was calibrated on the basis of the tests, and this way the shear bond strength and the coefficient of friction between the concrete and the recycled FRP laminate were assessed. [ABSTRACT FROM AUTHOR]

The design of wind turbines has been continually evolving to enhance aerodynamic efficiency, which is crucial for improving energy conversion and reducing operational costs. One promising technique is the application of the Co-Flow Jet (CFJ) method, which utilizes simultaneous blowing and suction to augment aerofoil performance. Despite its potential benefits, the relationship between aerofoil thickness and the resulting improvements in lift and drag coefficients has not been thoroughly explored, especially for the National Renewable Energy Laboratory (NREL) aerofoils commonly used in wind turbine applications. This study utilizes computational fluid dynamics (CFD) simulations in order to investigate the aerodynamic efficiency improvements of the NREL S826, NREL S825, and NREL S818 aerofoils through the application of the CFJ technique. Various configurations with different blowing (B) and suction (S) configurations were tested, including 0.08B-0.7S, 0.08B-0.8S, 0.1B-0.7S, and 0.2B-0.7S configurations. The results demonstrate that the S826-0.2B-0.7S, S825-0.2B-0.7S, and S818-0.08B-0.7S configurations yield the most significant enhancements at a common momentum coefficient (Cm) of 0.08. Specifically, there were increases in lift coefficients by about 51.1%, 66.38%, and 109%, and improvements in lift-to-drag ratios by about 11.5%, 14.38%, and 146.18% for the S826-0.2B-0.7S, S825-0.2B-0.7S and S818- 0.08B-0.7S configurations, respectively. [ABSTRACT FROM AUTHOR]

This paper aimed to understand the AE signal characteristics and damage mechanism of wind turbine blade main spar materials with different defects during the damage evolution process. According to the typical delamination and wrinkle defects in wind turbine blades, the GFRP composite with defects is artificially prefabricated. Through acoustic emission experiments, the mechanical properties and acoustic emission characteristic trends of wind turbine blade main spar composites with different defects under tensile loading conditions were analyzed, and the damage evolution mechanism of different defects was explained according to the microscopic results. The results show that the existence of artificial defects will not only affect the mechanical properties of composite materials but also affect the damage evolution process of the materials. The size and location of delamination defects and the different aspect ratio of the wrinkle defects have a certain influence on the damage mechanism of the material. K-means cluster analysis of AE parameters identified the damage models of GFRP composites. The types of damage modes of delamination defects and wrinkle defects are the same, and the range of characteristic frequency is roughly the same. This study has important reference significance for structural damage monitoring and damage evolution research of wind turbine blade composites. [ABSTRACT FROM AUTHOR]

Wind turbine blades are critical components of wind energy systems, and their structural health is essential for reliable operation and maintenance. Several studies have used time-domain and frequency-domain features alongside machine learning techniques to predict faults in wind turbine blades, such as erosion and cracks. However, a key gap remains in integrating these methods into a unified framework for fault prediction, which could offer a more comprehensive solution for diagnosing faults. This paper presents an approach to classify faults in wind turbine blades by leveraging well-known signals and analysis with machine learning techniques. The methodology involves a detailed feature engineering process that extracts and analyzes features from the time and frequency domains. Open-source vibration data collected from an experimental setup (where a small wind turbine with an artificially eroded and cracked blade was tested) were utilized. The time- and frequency-domain features were extracted and analyzed using various machine learning algorithms. It was found that erosion and crack faults have unique time- and frequency-domain features. The crack fault introduces an amplitude modulation in the vibration time wave, which produces sidebands around the fundamental frequency in the frequency domain. However, erosion fault introduces asymmetricity and flatness to the vibration time wave, which produces harmonics in the frequency-domain plot. The results also highlighted that utilizing both time- and frequency-fault features enhances the performance of the machine learning algorithms. This study further illustrates that even though some machine learning algorithms provide similar high classification accuracy, they might differ in quantifying error Types I, II, and, III, which is extremely important for maintenance engineers, as it might lead to undetected fault events and false alarm events. [ABSTRACT FROM AUTHOR]

Researchers often explore metaheuristic algorithms for their studies. These algorithms possess unique features for solving optimization problems and are usually developed on the basis of real-world natural phenomena or animal and insect behavior. Numerous fields have benefited from metaheuristic algorithms for solving real-world optimization problems. As a renewable energy source, offshore wind energy is a rapidly developing subject of research, attracting considerable interest worldwide. However, designing offshore wind turbine systems can be challenging because of the large space of design parameters and different environmental conditions, and the optimization of offshore wind turbines can be extremely expensive. Nevertheless, advanced optimization methods can help to overcome these challenges. This study explores the use of metaheuristic algorithms in optimizing the design of wind turbines, including wind farm layout and wind turbine blades. Given that offshore wind energy relies more heavily on subsidies than fossil fuel-based energy sources, lowering the costs for future projects, particularly by developing new technologies and optimizing existing methods, is crucial. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In structural recycling of wind turbine blades, two options are often distinguished: reuse and repurpose. The latter was the main subject of the present research carried out by the authors in a research consortium with the leading Polish industry waste recycler. The main goal of the project was to develop, design, and demonstrate the first domestic footbridge made of decommissioned wind turbine blades, taking into account the review of existing ideas. This paper presents an experimental investigation to determine the material parameters and to evaluate the structural behavior of a decommissioned wind turbine blade to be adopted for a footbridge. Terrestrial laser scanning and comprehensive material testing were performed according to ASTM standards to determine the actual blade geometry, the stacking sequence, and the mechanical properties of the blade composite materials. The experimentally determined strengths, elastic moduli, and Poisson's ratios of the composites extracted from the shell and the spar cap along the blade were very high and definitely sufficient for the fiber-reinforced polymer bridge girders. Then, a four-point edgewise bending test was performed on an 11 m section of the blade to evaluate its structural behavior: stiffness, ultimate strength, global safety factor, and fatigue life. The full-scale model of the blade bridge girder behaved linearly elastic in the full load range up to 1,250 kN of the total load, did not reach the ultimate carrying capacity, and exhibited only small local damages (laminate cracking). The results of these tests revealed that the LM 29.1-type wind turbine blades were suitable to be reutilized as main girders for a footbridge. Using the presented research results, the first bridge in the world made of decommissioned wind turbine blades was designed and installed in the late fall of 2021 in Poland. [ABSTRACT FROM AUTHOR]

The fatigue behavior of large wind turbine blades is complex and stochastic due to their complex structure and operating environment. This paper focuses on developing a probabilistic fatigue life assessment method for wind turbine blades considering the uncertainties from wind velocity, material mechanical properties, pitch angle, and layer thickness. To improve the efficiency of stochastic fatigue behavior analysis of wind turbine blade, unidirectional fluid‐structure coupling (UFSC) and bidirectional fluid‐structure coupling (BFSC) analysis are employed to analyze the stochastic response. Then, Gaussian process regression (GPR) and Bayesian updating are combined to establish the stochastic fatigue behavior prediction model for wind turbine blade. On this basis, a modified S‐N curve formulation is proposed, and the fatigue life of wind turbine blade is analyzed by the modified S‐N curve and compared with the three‐parameter Weibull model. The results indicate that the proposed method for fatigue life assessment has better accuracy. The proposed probabilistic fatigue life assessment method with high accuracy and high efficiency, which is beneficial for the fatigue reliability design of wind turbine blades. [ABSTRACT FROM AUTHOR]

Wind energy is a renewable energy source with a significant impact on the date for harnessing it. Different types of wind turbines (WTs) are being built to generate affordable, dependable, and eco-friendly renewable wind energy. Over time, cracks are found to be developed in the blades of the WTs, which is considered the most common type of damage that ultimately causes the catastrophic failure of the structures. This study aims to develop a structural health monitoring (SHM) framework for localizing cracks of a WT blade using a convolutional neural network (CNN)–based deep learning algorithm. With that objective, the NACA (National Advisory Committee for Aeronautics) 63-412 profile (WT blade) of length 29 m was modelled in finite element analysis (FEA) ANSYS 2022 R2. A crack is introduced to the model by making a groove at different blade locations. The mode shape and natural frequencies are obtained and validated with those reported in the literature. Further, the blade is excited by an impact load applied at the tip of the blade, and acceleration time histories are collected. The acceleration time history data are converted to scalogram images and fed into the CNN algorithm for damage classification and localization. In this study, the concept of class activation maps is also utilized for visual representations of the input images' areas that significantly influence a class's classification score. The classified results show that using CNN can successfully localize the region of the cracks and motivate us to examine it on a laboratory-based model. [ABSTRACT FROM AUTHOR]

Numerical simulation technology is a crucial tool for reducing costs and increasing efficiency in the wind power industry. However, with the development of large-scale wind turbines, the computational cost of numerical simulation has gradually increased. This paper uses the geometric similarity, structural similarity criterion, Reynolds similarity and boundary layer theory to establish a scaled model of the geometric three-dimensional shape, composite material, and finite element mesh of large wind turbine blades. The study analyzes the aerodynamic, gravitational, and centrifugal load variations within the scaled model. The proportional relationship between the scaled model's operating parameters, the numerical simulation's environmental parameters, and the mechanical response parameters is established. These parameters are coordinated to ensure the similarity of the blade structure and the fluid dynamics. For a geometric scale factor of 0.316, the relative difference in maximum deflection is 4.52%, with a reduction in calculation time by 48.1%. On the premise of ensuring the calculation accuracy of the aerodynamic and structural response of the blade, the calculation efficiency is effectively improved. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Predicting the dynamic response at unmeasured locations is of great interest in the study of structural dynamic systems to address limitations of number of available sensors and inaccessibility of measurements in enclosed or hazardous environments. Dynamic response at measured points on a structure can be expanded to predict response for unmeasured points through model-based expansion, but this approach requires a correlated (or calibrated) finite element model. To avoid finite element model dependency and the need for correlation, model-free dynamic response prediction techniques have been proposed for plate-type structures and cylindrical-shell structures. However, a limitation of those techniques is that only the 1D (one-dimensional) dynamic response along one direction of the 2D (two-dimensional structure) could be studied using the developed shape functions. Methods: In this work, we present a model-free method that overcomes these limitations in order to predict the 3D dynamic response for unmeasured locations for complicated three-dimensional structures. This work develops a new model-free method based on three-dimensional Chebyshev polynomial shape functions for predicting the 3D dynamic response of the three-dimensional utility structures. The method is based on orthogonal Chebyshev polynomials as shape functions to decompose the physical dynamic response of the measurement points into a set of polynomial dynamic response. The expansion is performed within the polynomial space from measurement points to the measurement points plus the unmeasured point. Then, the expanded polynomial space is mapped back to physical space to obtain the physical dynamic response at the unmeasured point. The advantage of the proposed method is that only the measured dynamic response data and geometric coordinates of the measurement points are needed. Namely, in this advantage, the external excitation applied to the structures and the boundary condition of the structures are not required to be quantified or known. Results and Conclusions: An accelerometer-based test and high-spatial-resolution 3D scanning laser Doppler vibrometer (SLDV) test on a wind turbine blade provide test data used to experimentally validate the application of the proposed method of predicting the three-dimensional dynamic response on the three-dimensional structures. Convergence studies are performed to evaluate the impact of the number of measurement points and the location of measurement points on the accuracy of the method. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Donghua University (Natural Science Edition) is the property of Journal of Donghua University (Natural Science) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A dynamic pitch strategy is usually adopted to improve the aerodynamic performance of the blade of a wind turbine. The dynamic pitch motion will affect the linear vibration characteristics of the blade. However, these influences have not been studied in previous research. In this paper, the influences of the rigid pitch motion on the linear vibration characteristics of a wind turbine blade are studied. The blade is described as a rotating cantilever beam with an inherent coupled rigid-flexible vibration, where the rigid pitch motion introduces a parametrically excited vibration to the beam. Partial differential equations governing the nonlinear coupled pitch-bend vibration are proposed using the generalized Hamiltonian principle. Natural vibration characteristics of the inherent coupled rigid-flexible system are analyzed based on the combination of the assumed modes method and the multi-scales method. Effects of static pitch angle, rotating speed, and characteristics of harmonic pitch motion on flexible natural frequencies and mode shapes are discussed. It shows that the pitch amplitude has a dramatic influence on the natural frequencies of the blade, while the effects of pitch frequency and pith phase on natural frequencies are little. [ABSTRACT FROM AUTHOR]

Lightning is the severest threaten to safe operation of wind turbines. In this letter, the authors present the first altitude‐triggered lightning experiment involving an elevated 12 m‐long wind turbine blade placed on the ground. A total of 50 precursors with amplitude over 62.9 A were observed through measurements of channel‐base current, fast electric field, and optical data. The air gap with around 3–5 m has been bridged between the wire's lower extremity and the metal blade tip during ascending of the rocket and it is observed to be luminous by slow framing rate camera. The precursors are classified into three groups, namely bipolar pulses, unipolar pulses, and group pulses. Excluding the precursors preceding the initial stage and M‐components at the late‐time of the initial stage, five stages are classified. In the first stage, the current remains limited at a relatively small value, while the electric field exhibited a slow rising behavior with positive polarity. In the second stage, the current starts to increase, and the electric field rapidly intensifies due to the accumulating charge, and the wire is assumed to experience an explosion. In the third stage, the reconnection process occurs. The current is characterized by a peak value of 1.45 kA with 10%–90% risetime of 10.4 μs. The electric fields suffer from notable decrease and are characterized by a microsecond‐scale V‐shape pulse. The current cutoff is quite short that almost not found. In the fourth step, the current is characterized by superimposed pulses. The final stage is the channel darkening. Plain Language Summary: Observation results are reported in detail about the altitude‐triggered lightning experiment involving an elevated 12 m‐long wind turbine blade placed on the ground. There are fruitful precursors prior to the beginning of the initial stage. The precursors demonstrate that the air gap with around 3–5 m has been bridged between the wire and the metal blade tip. The precursors are grouped into three groups, namely bipolar pulses, unipolar pulses, and group pulses. The initial stage is classified into five periods. The triggering wire is believed to be vapourized during the second stage. The so‐called initial current variation (ICV), also called reconnection process, occurs at the third stage. The superimposed pulses are found immediately after the reconnection process in the fourth stage. The late‐time of the initial stage is also characterized by superimposed pulses associated with M‐components. This work is potentially helpful to understand the physical process lightning strikes a wind turbine, and design lightning protection strategies for wind turbines. Key Points: First altitude‐triggered lightning experiment associated with an elevated 12 m‐long wind turbine blade has been conducted through simultaneous measurements of current, electric fields and optical dataThe 50 precursors over 62.9 A proceeding the initial stage are classified into three groups: (a) bipolar pulses with the notably initial positive peak and followed by the negative excursion; (b) unipolar pulses with the notably initial positive peak but with quite flat late‐time response; and (c) group pulsesFive stages associated with channel reestablishment are classified according to the measured current and electric field, in which the current cutoff is quite short that almost not found [ABSTRACT FROM AUTHOR]

The flammability levels, flame retardancy ratings, and reaction-to-fire (fire response) properties (under five radiant heat fluxes, i.e., 15, 25, 35, 50, and 75 kW m−2) for same real E-glass fiber-reinforced unsaturated polyester resin (UPR) composite wind turbine blade (WTB) samples were determined by experimental techniques like limiting oxygen index (LOI), vertical flame test (VFT), and cone calorimeter test (CCT). Based on typical CCT results (main test parameters), thermal and non-thermal hazard assessment index systems were selected, calculated, and compared to deduce corresponding hazard characteristics of the blade samples. The WTB shows a LOI value of 25.10% (combustible) and a non-rated (NR) UL (Underwriters Laboratories) 94 classification according to the after-flame time criterion. CCT analyses indicate that higher external heat fluxes correspond to increased peak heat release rate (PkHRR), total heat release (THR), and mass loss rate (MLR) values, and reduced ignition time (tig), flame duration (tfl), and overall flame (combustion) duration (FD) values. Meanwhile, CCT analyses indicate that higher external heat fluxes result in elevated specific extinction area (SEA), rate of smoke released (RSR), total smoke released (TSR), CO yield (COY), and CO production rate (COP) values, and relatively lower CO2 yield (CO2Y) and CO2 production rate (CO2P) values. These results reflect real WTB fires will pose severe situations with noticeable thermal and non-thermal hazards. Multiple physical and chemical evolution processes undergo in burning processes of such fires with higher PkHRR values through heat releases, transfers, exchanges, and feedback. Composite blade materials may be largely deformed and disintegrated in faster rates. Burning blade blocks may form spotting fires and cause secondary ground fires. Local air quality, visibility levels, working, and health conditions of related persons may be worsened. It is really urgent to develop mature, effective, novel, and even revolutionary fire protection and suppression technologies for such fires. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Damage monitoring is an essential step to understand fatigue damage growth in composite wind turbine blades and for reliable lifetime prediction. The current study is an experimental investigation of fatigue delamination induced by an intentionally embedded defect in the spar cap of a 31 m wind turbine blade. A constant cyclic flap-wise bending was applied to the blade for 320,000 cycles. Delamination growth is identified and measured by visual inspection, acoustic emission (AE), and infrared thermography of the blade surface. It was observed that the area of delaminated regions grew faster during the early cycles, then their growth rates decreased, and the interlayer cracks reached stable growth. The experiment shows fatigue delamination develops gradually in the spar cap and allows monitoring of the damage before reaching a critical stage. The ability of AE and thermography methods to detect subsurface damage is demonstrated by the identification of steady delamination growth during cyclic load. Damage localization by both methods is in good agreement with the delamination location. Most acoustic activities are spotted in the boundaries of delaminated regions, and the position of a significant number of acoustic activities with the highest energy content correlates with the location of delamination crack fronts. It is shown that the surface temperature distribution contour indicates the shape of the largest delaminated region, and the growth of the hot region area correlates with damage propagation. However, multiple delaminations through the thickness cannot be discriminated from the thermal images. [ABSTRACT FROM AUTHOR]

We designed 60% thick airfoil to improve the aerodynamic performance in the root region of wind turbine rotor blades, taking into account current constraints. After an extensive literature review and patent research, a design methodology (including the considerations of simple manufacturing) was set up, and extensive 2D- and 3D-CFD investigations with four codes (Xfoil, MSES, ANSYS fluent, and DLR-tau) were performed, including implementation inside a generic 10 MW test-blade (CIG10MW). Comparison with results from Blade Element Momentum (BEM) methods and the estimation of 3D effects due to the rotating blade were undertaken. One specific shape (with a pronounced flat-back) was selected and tested in the Deutsche WindGuard aeroacoustic Wind Tunnel (DWAA), in Bremerhaven, Germany. A total of 34 polars were measured, included two trailing edge shapes and aerodynamic devices such as vortex generators, gurney flaps, zig-zag tape, and a splitter plate. Considerable changes in lift and drag characteristics were observed due to the use of aerodynamic add-ons. With the studies presented here, we believe we have closed an important technological gap. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the continuous development of wind energy resources, wind turbines have become a crucial element in the field of green energy. However, various malfunctions may occur during their operation, affecting performance and lifespan. To ensure the safety and efficiency of wind turbines, regular inspections and maintenance are essential. In recent years, rapid advancements in unmanned aerial vehicle (UAV) technology have opened new possibilities for the inspection and maintenance of wind turbines. The blades of wind turbines are the most critical components, and this review paper provides a comprehensive analysis of UAV applications in the detection, inspection, and diagnosis of wind turbine blades. It focuses on key UAV inspection technologies, highlighting their advantages and disadvantages in both static and rotating wind turbine blades. Additionally, the paper analyses control algorithms used by UAVs for blade inspection, verifying their accuracy and practicality in this field. Based on these findings, future technological trends are proposed, including UAV autonomous navigation, edge computing-based online monitoring, and intelligent fault diagnosis. It is anticipated that UAV inspection technology will increasingly play a significant role in the inspection and maintenance of wind turbine blades in the future. [ABSTRACT FROM AUTHOR]

Graphene platelets (GPLs) are gaining popularity across various sectors for enhancing the strength and reducing the weight of structures, thanks to their outstanding mechanical characteristics and low manufacturing cost. Among many engineering structures, wind turbine blades are a prime candidate for the integration of such advanced nanofillers, offering potential improvements in the efficiency of energy generation and reductions in the construction costs of support structures. This study aims to explore the potential of GPLs for use in wind turbine blades by evaluating their impact on material costs as well as mechanical performance. A series of finite element analyses (FEAs) were conducted to examine the variations of mechanical performances—specifically, free vibration, bending, torsional deformation, and weight reductions relative to conventional fiberglass-based blades. Details of computational modeling techniques are presented in this paper. Based on the outcomes of these analyses, the mechanical performances of GPL-reinforced wind turbine blades are reviewed along with a cost–benefit analysis, exemplified through a 5MW-class wind turbine blade. The findings affirm the practicality and benefits of employing GPLs in the design and fabrication of wind turbine blades. [ABSTRACT FROM AUTHOR]

The wind energy sector is experiencing rapid growth, marked by the expansion of wind farms and the development of large-scale turbines. However, conventional manual methods for wind turbine operations and maintenance are struggling to keep pace with this development, encountering challenges related to quality, efficiency, and safety. In response, unmanned aerial vehicles (UAVs) have emerged as a promising technology offering capabilities to effectively and economically perform these tasks. This paper provides a review of state-of-the-art research and applications of UAVs in wind turbine blade damage detection, operations, and maintenance. It encompasses various topics, such as optical and thermal UAV image-based inspections, integration with robots or embedded systems for damage detection, and the design of autonomous UAV flight planning. By synthesizing existing knowledge and identifying key areas for future research, this review aims to contribute insights for advancing the digitalization and intelligence of wind energy operations. [ABSTRACT FROM AUTHOR]

Over the course of many years of use, impingement wear from dust, sand, and other materials can damage wind turbine blades, necessitating repairs and other maintenance work. Recently, wind turbine operators are turning to protective films, which allow such work to be completed more efficiently, as an alternative to the conventional approach of using paint to repair wind turbine blades. However, the erosion resistance characteristics of repaired blades remain unclear. In this study, we create paint- and protective film-coated samples to reproduce repairs, measure their erosion resistance, and study underlying factors in an effort to verify the erosion resistance of repaired materials and associated mechanisms. The low erosion resistance of GFRP can be significantly improved by applying a protective film made of a ductile material. Such material effectively protects the surface of the GFRP. Moreover, the erosion resistance of protective films made from polyurethane material is superior to that of paint. We recommend use of protective film with wind turbine blades when manufacturing blades and regular maintenance. [ABSTRACT FROM AUTHOR]

In order to solve the end-effector force control response speed hysteresis and mechanical vibration problems caused by parameter perturbations and other disturbances during the processing of wind turbine blades by polishing robots, this paper proposes a robot pneumatic end-effector polishing force control strategy based on adaptive sliding mode backstepping algorithm. Based on the establishment of the mathematical model of the end-effector pneumatic system, a smooth and continuous sliding mode control law is adopted to solve the design conflict between sliding mode control theory and backstepping method, and to suppress output chattering in sliding mode control. By utilizing the insensitivity of the sliding mode control to the system model, the influence of matching disturbances on the system is eliminated. The non-matching disturbances of the known model are accurately compensated by backstepping control, and parameter uncertainty is effectively handled by adaptive control. Simulation and experimental results show that this method can effectively solve the uncertainty of system parameters and has good disturbance suppression ability, significantly improving the surface quality of wind turbine blades. [ABSTRACT FROM AUTHOR]

This work concentrates on the design parameters of a turbine blade for a small-scale solar chimney plant. The pitch angle (θ), relative wind angles (ϕ and ψ), lift force (FL) and relative chord length (lcr) of the turbine blade are determined. Betz and Bernoulli's theories were used for estimating and optimizing the above blade parameters. The coefficients of power, drag, lift and thrust forces are estimated and analyzed. Two wind speeds were considered. One represented higher speed (10 m/s) and the other for lower speed (2 m/s). At 10 m/s, the required rotor diameter is drastically reduced for producing the same power output. At 2 m/s, θ, ϕ, ψ and FL were optimized and they are; θ = 18.4°, ϕ = 26.4°, ψ = 75.6° and FL = 0.0073 N for maintaining the maximum power (P) of 0.026 W. The required diameter for the rotor blade is estimated and is varied from 0.66 to 6.56 m for producing a power range of 1–100 W. At 10 m/s, the optimized parameters are; θ = 42.9°, ϕ = 50.94° and ψ = 20.39° and FL = 0.4082 N for reaching the maximum P of 2.538 W. The estimated results were validated with existing studies and observed a good match. [ABSTRACT FROM AUTHOR]

Rain erosion induced by raindrops impacting wind turbine blades at high velocity can change the aerodynamic characteristics of the blades and increase maintenance costs. Previous numerical studies on rain erosion have not considered the curvature of the blade leading-edge surfaces and assumed them to be flat surfaces. This study established a fluid-solid coupled numerical model combining the finite element method and smooth particle hydrodynamics. It models a water droplet with a diameter of 2.74 mm impacting the curved leading-edge surface of wind turbine blades with radii of curvature of 1.35 mm, 6.75 mm, 67.5 mm, and infinite at 110 m/s, and the effects of the radius of curvature on the impact response were analyzed. The results show that as the radius of curvature of the leading-edge surface increases, the surface obstructs the water droplet more significantly, and the lateral jetting of the water droplet is enhanced. A larger radius of curvature causes more droplet impact energy to be transferred to the curved surface, increasing the contact force between the water droplet and the surface. The increased transferred impact energy results in higher stress and plastic strain values. The decrease in the radius of curvature of a curved surface increases the error in the stress and strain results obtained by assuming it to be a flat surface.

Wind energy, as a renewable energy source, is becoming increasingly important. The maintenance and damage detection of wind turbine blades are particularly crucial. For this purpose, the study aims to optimize the You Only Look Once (YOLO) processing algorithm for drone images to improve the detection efficiency. Firstly, the damage images captured by drones are preprocessed and optimized, including deblurring, noise reduction, and image enhancement. Subsequently, the YOLOv5 model is improved in terms of structure and regression function, and a novel damage detection model is proposed. The research results indicated that the minimum loss function value of the improved model was 2.75, the average accuracy was 95 %, and the highest intersection over union was 91 %. After simulation testing, the detection effect of this model on abrasion, crackle, edge cracking, and coating peeling images was significantly better than other models in the same series. Its average time was as short as 2.43 s, reaching a maximum frame rate of 35.46. From this, the combination of drone image technology and improved image processing algorithm has a positive impact on improving the operational efficiency and safety of wind turbine blades. Compared with the traditional methods, the proposed model has significant advantages in terms of accuracy and real-time performance of damage detection, providing a new technical means for efficient maintenance of wind turbines. Meanwhile, the method shows high robustness and reliability in different types of damage detection, demonstrating the extensive potential in practical applications.

We designed 60% thick airfoil to improve the aerodynamic performance in the root region of wind turbine rotor blades, taking into account current constraints. After an extensive literature review and patent research, a design methodology (including the considerations of simple manufacturing) was set up, and extensive 2D- and 3D-CFD investigations with four codes (Xfoil, MSES, ANSYS fluent, and DLR-tau) were performed, including implementation inside a generic 10 MW test-blade (CIG10MW). Comparison with results from Blade Element Momentum (BEM) methods and the estimation of 3D effects due to the rotating blade were undertaken. One specific shape (with a pronounced flat-back) was selected and tested in the Deutsche WindGuard aeroacoustic Wind Tunnel (DWAA), in Bremerhaven, Germany. A total of 34 polars were measured, included two trailing edge shapes and aerodynamic devices such as vortex generators, gurney flaps, zig-zag tape, and a splitter plate. Considerable changes in lift and drag characteristics were observed due to the use of aerodynamic add-ons. With the studies presented here, we believe we have closed an important technological gap.

In order to study the structural performance of the new bend-twist coupling blade, NREL 5 MW blade was taken as the prototype, and the geometric model of the blade was established by using NX Open Grip parameterization language. The composite lamination design was carried out in accordance with the real processing technology, and the aerodynamic force of the blade was obtained by the computational fluid dynamics (CFD) method. The bend-twist coupling characteristics, harmonic response and strength of conventional and bending-torsional coupling blades were analyzed respectively. The results show that the blade tip displacement increases with the increase of the web deflection. For the same angle, the blade tip displacement of γ > 0 blades was smaller than that γ < 0 blades. The bend-twist coupling effect is the most obvious when γ = 10° and 15°. Compared with the conventional blade, the second-order displacement responses of bend-twist coupling blades are significantly reduced. The γ = 15° blade can reduce the stress on the surface and has a good load reduction performance.

With the trend towards larger and lighter designs of wind turbines, blades are progressively being developed to have longer and more flexible configurations. Under standstill conditions, the separated flow induced by a wide range of incident flow angles can cause complex aerodynamic elastic phenomena on blades. However, classical momentum blade element theory methods show limited applicability at high angles of attack, leading to significant inaccuracies in wind turbine performance prediction. In this paper, the geometrically accurate beam theory and high-fidelity CFD method are combined to establish a bidirectional fluid–structure coupling model, which can be used for the prediction of the aeroelastic response of wind turbine blades and the analysis of fluid–structure coupling. Aeroelastic calculations are carried out for a single blade under different working conditions to analyze the influence of turbulence, gravity and other parameters on the aeroelastic response of the blade. The results show that the dominant frequency of the vibration deformation response in the edgewise direction is always the same as the first-order edgewise frequency of the blade when the incoming flow condition is changed. The loading of gravity will make the aeroelastic destabilization of the blade more significant, which indicates that the influence of gravity should be taken into account in the design of the aeroelasticity of the wind turbine. Increasing the turbulence intensity will change the dominant frequency of the vibration response in the edgewise direction, and at the same time, it will be beneficial to the stabilization of the aeroelasticity response. [ABSTRACT FROM AUTHOR]

A study was conducted on the changes in mechanical properties and fatigue failure characteristics due to voids, one of the fabrication defects in composite materials. This study was primarily based on glass fiber fabrics applied to wind turbine blades and their material properties were predicted through micro and meso modeling of composite materials by simulating random defects including voids. As the wind turbine blades become larger, various defects develop. The fundamental changes in the materials' properties due to voids were predicted through homogenization methods and Representative Volume Element (RVE), and the failure properties were obtained through progressive failure analysis by applying virtual coupons according to ASTM D3090 and ASTM D6641. The progressive failure was identified using the Matzenmiller–Lubliner–Taylor (MLT) failure condition, and the fatigue failure characteristics were assessed through the Tsai–Hill 3D load. [ABSTRACT FROM AUTHOR]

The core of the modern lightweight wind turbine blade may be a truss structure based on carbon-fiber rods connected to stiff ribs. A specialized robot manufactures these structures by spatially winding impregnated carbon fibers around pre-positioned ribs with cutouts for securing the fiber bundle. Quantity of the ribs, their positions, and positions of the rods can vary, making this type of blades well-suited for optimization. We present an optimization approach for designing the core of a lightweight wind turbine blade. Our approach involves dividing the task into two stages and utilizing multiple optimization algorithms at each stage. Proposed approach used the FUD, DAJA, and Evolution Strategy algorithms. To test the approach, an existing blade structure with known characteristics was used. Comparison of the resulting design with the original one reveals 53 percent smaller value of objective function. These results demonstrate the effectiveness of applying the proposed approach. New approach allows for the optimization of complex rod with ribs' structures that cannot be optimized using standard optimization method. This will hopefully result in a significant decrease of wind turbine production cost. [ABSTRACT FROM AUTHOR]

The leading-edge erosion of a wind turbine blade was tested using a whirling arm rain erosion tester, whose rotation rate is considerably higher than that of a full-scale wind turbine owing to the scale effect. In this study, we assessed the impact pressure of droplets on a wet surface of wind turbine blades using numerical simulation of liquid droplet impact by solving the Navier–Stokes equations combined with the volume-of-fluid method. This was conducted in combination with an estimation of liquid film thickness on the rotating blade using an approximate solution of Navier–Stokes equations considering the centrifugal and Coriolis forces. Our study revealed that the impact pressure on the rain erosion tester exceeded that on the wind turbine blade, attributed to the thinner liquid film on the rain erosion tester than on the wind turbine blade caused by the influence of centrifugal and Coriolis forces. This indicates the importance of correcting the influence of liquid-film thickness in estimating the impact velocity of droplets on the wind turbine blade. Furthermore, we demonstrated the correction procedure when estimating the impact velocity of droplets on the wind turbine blade. [ABSTRACT FROM AUTHOR]

This study employed experimental methods to systematically investigate the bending behavior of composite materials at high temperatures. The biaxial warp-knitted fabric (BWKC) and quadaxial warp-knitted fabric (QWKC) were selected as reinforcement and the mixture solution of epoxy resin and curing agent were selected as matrix. The composite specimen was fabricated by vacuum assisted resin film (VARI). Taking into influence of temperature on the bending behavior of composites for wind turbine blades, further investigations have been conducted to analyze the influence of temperature on the mechanical properties of composites. The quasi-bending behavior of BWKC and QWKC in 0°–90°directions at different service temperatures (20℃, 45℃ and 70℃) were analyzed at macro-scale and micro-scale. Results show that the bending strength and modulus were decreased with the increase of temperature. The ultimate normalized strength of BWKC and QWKC composites were decreased by 20.36–23.56%. The behavior such as the stress–strain curves were also obtained. The relationships between bending behavior and temperatures are also obtained by nonlinear fitting with the experimental data, which could be used to predict the bending properties at different temperatures. [ABSTRACT FROM AUTHOR]

Durable elastomeric deicing coatings were developed for the anti-icing and deicing of wind turbine blades in this study. Our developed deicing coatings demonstrated extremely low ice adhesion strength (~15 kPa). Silica was added to enhance the icephobic surfaces' durability. The life of the deicing coating with silica was extended by 1.2 times. After 168 h of xenon lamp irradiation, there were no significant changes in the chemical composition of the coatings. Due to the increasing roughness and the decreasing tensile modulus, the contact angle of the aged coatings decreased by 14°. Further outdoor research was carried out on a wind farm for two months to investigate the influence of natural insolation and wind erosion on the elastic deicing coatings. The aged coating still maintained a high hydrophobicity and low ice adhesion strength. The contact angle stabilized at 107°, and the ice adhesion strength was 75% lower than that of the uncoated wind turbine blade. The elastomeric deicing coatings had three advantages: a lagging freezing time, low ice accumulation, and a short icing/deicing cycle. The results of field experiments on the naturally aged coatings showed that the freezing time of the coated blade was delayed by 20 min, and the ice on the coated blade was 29% thinner than that on the uncoated blade. [ABSTRACT FROM AUTHOR]

The wind energy sector faces a persistent challenge in developing sustainable solutions for decommissioned Wind Turbine Blades (WTB). This study utilises Lifecycle Assessment (LCA) to evaluate the gate-to-gate carbon footprint of high-profile disposal and recycling methods, aiming to determine optimal strategies for WTB waste treatment in the UK. While this article analyses the UK as a case study, the findings are applicable to, and intended to inform, recycling strategies for WTB waste globally. Long-term sustainability depends heavily on factors like evolving energy grids and changing WTB waste compositions and these must be considered for robust analysis and development strategy recommendations. In the short to medium term, mechanical recycling of mixed WTB waste is sufficient to minimise Global Warming Potential (GWP) due to the scarcity of carbon fibre in WTB waste streams. Beyond 2040, carbon fibre recycling becomes crucial to reduce GWP. The study emphasises the importance of matching WTB sub-structure material compositions with preferred waste treatment options for the lowest overall impact. Future development should focus on the extraction of carbon fibre reinforced polymer (CFRP) structures in WTB waste streams, commercialising large-scale CFRP structure recycling technologies, establishing supply chains, and validating market routes for secondary carbon fibre products. In parallel, scaling up low-impact options, like mechanical recycling, is vital to minimise WTB waste landfilling. Developing viable applications and cost-effective market routes for mechanical recyclates is necessary to displace virgin glass fibres, while optimising upstream recycling processes based on product requirements. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent trends, a rising demand for renewable energy has driven wind turbines to larger proportions, where lighter blade designs are often adopted to reduce the costs associated with logistics and production. This causes modern utility-scale wind turbine blades to be inherently more flexible, and their amplified aeroelastic sensitivity results in complex multi-physics reactions to variant atmospheric conditions, including dynamic patterns of aerodynamic loading at the rotor and vortex structure evolutions within the wake. In this paper, we analyze the influence of inflow variance for wind turbines with large, flexible rotors through simulations of the National Rotor Testbed (NRT) turbine, located at Sandia National Labs' Scaled Wind Farm Technology (SWiFT) facility in Lubbock, Texas. The Common Ordinary Differential Equation Framework (CODEF) modeling suite is used to simulate wind turbine aeroelastic oscillatory behavior and wind farm vortex wake interactions for a range of flexible NRT blade variations, operating in differing conditions of variant atmospheric flow. CODEF solutions of turbine operation in Steady-In-The-Average (SITA) wind conditions are compared to SITA wind conditions featuring a controlled gust-like pulse overimposed, to isolate the effects of typical wind fluctuations. Finally, simulations of realistic time-varying wind conditions from SWiFT meteorological tower measurements are compared to the solutions of SITA wind conditions. These increasingly complex atmospheric inflow variations are tested to show the differing effects evoked by various patterns of spatiotemporal atmospheric flow fluctuations. An analysis is presented for solutions of wind turbine aeroelastic response and vortex wake evolution, to elucidate the consequences of variant inflow, which pertain to wind turbine dynamics at an individual and farm-collective scale. The comparisons of simulated farm flow for SITA and measured fluctuating wind conditions show that certain regions of the wake contain up to a 12% difference in normalized axial velocity, due to the introduction of wind fluctuations. The findings of this study prove valuable for practical applications in wind farm control and optimization strategies, with particular significance for modern utility-scale wind power plants operating in variant atmospheric conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Offshore wind turbines operating in frigid and humid climates may encounter icing on the blade surface. This phenomenon adversely impacts the aerodynamic efficiency of the turbine, consequently diminishing power generation efficacy. Investigating the distribution characteristics of icing on the blade surface is imperative. Hence, this study undertook icing wind tunnel tests on segments of DU25 airfoil, a prevalent type for offshore wind turbines, to examine such characteristics as different chord lengths and angles of attack. The results show a simultaneous increase in the blade icing area and growth rate of the net icing area with augmenting the chord length and angles of attack. The total icing area rate decreases by a factor of two when the chord length is doubled. The relative positioning of icing and the average icing thickness remain consistent across the airfoil blades with varying chord lengths. Comparing the icing shapes on blades of varying scales shows a similarity ranging from 84.06% to 88.72%. The results of this study provide insight into the icing characteristics of offshore wind turbines. [ABSTRACT FROM AUTHOR]