Wind Turbine Blades Research Articles

Thermal Inspection of Subsurface Defects in Wind Turbine Blade Segments Under the Natural Solar Condition

Thermal Inspection of Subsurface Defects in Wind Turbine Blade Segments Under the Natural Solar Condition

Boundary layer stability on a rotating wind turbine blade section

Wall-resolved large eddy simulations of the flow on a rotating wind turbine blade section are conducted to study the rotation effects on laminar-turbulent transition on the suction surface. A chord Reynolds number of 1×105 and angles of attack (AoA) of 12.8°, 4.2°, and 1.2° are considered. Simulations with and without rotation are performed for each AoA. For AoA=12.8°, rotation increases the reverse flow from 7% of the free-stream velocity in the non-rotating case to 16% of it in the rotating case in the laminar separation bubble (LSB), triggering an oblique instability mechanism in the latter, leading to a faster breakdown to small-scale turbulence. However, rotation delays transition and reattachment in 3%–4% of the chord due to the acceleration of the boundary layer upstream of the LSB, which is subject to a strong adverse pressure gradient (APG), stabilizing Tollmien–Schlichting (TS) waves. Regarding AoA=4.2° and 1.2°, rotation slightly decelerates the attached boundary layer since the APG is very mild but accelerates the separated flow downstream, stabilizing Kelvin–Helmholtz (KH) modes. This mitigates the oblique instability mechanism and slows down the breakdown of KH vortices in the rotating case. In these cases, the transition location is little affected by rotation, possibly due to a rotation-independent absolute instability. Rotation also generates a spanwise tip-flow in the LSB for AoA=4.2° and 1.2°, which is highly unstable and triggers stationary and traveling crossflow modes. Nevertheless, the amplitudes of these modes remain too low to trigger transition.

Study on internal heat transfer characteristics of a wind turbine blade

Abstract Based on the theory of computational fluid dynamics and computational heat transfer, ANSYS FLUENT software is used to simulate the internal space flow field and temperature field of a wind turbine blade. The temperature field distribution of the blade was studied under different conditions, and the heating law inside the blade was analyzed. The results show that the temperature of the blade tip, the end face on both sides of the web and the area near the outlet of the wind turbine are obviously lower, and the low temperature phenomenon can be alleviated simply by increasing the inlet speed and temperature of the blade. Compared with increasing the inlet air temperature, increasing the inlet air speed of the blade can more effectively enhance the convective heat transfer of the air, so as to increase the temperature of the blade surface rapidly. When the inlet wind speed of the wind turbine blade is 30m/s and the inlet temperature is 100°C, the average temperature of the outer wall of the blade is about 50°C, which can meet working requirements of the blade. It takes about 20 seconds from the beginning of heating to the internal temperature of the blade reaching a stable state.

A Novel Lift Controller for a Wind Turbine Blade Section Using an Active Flow Control Device Including Saturations: Experimental Results

A Novel Lift Controller for a Wind Turbine Blade Section Using an Active Flow Control Device Including Saturations: Experimental Results

An asset management modelling framework for wind turbine blades considering monitoring system reliability

By incorporating information about asset condition from a monitoring system, engineers can utilize asset management models to manage maintenance activities on wind turbine blades throughout their lifespan. This can lower operating and maintenance costs and increase the life of the blades. The asset management model relies on the monitoring system as a source of information, however, commonly the reliability of the monitoring system is not considered. This paper presents a wind turbine blade asset management Petri net (PN) model that covers the blade asset management process, including degradation, inspection, condition monitoring (CM), and maintenance processes. The paper proposes two contributions. Firstly, while taking into account detailed industry guidelines, the developed model can forecast the future blade condition for a given asset management strategy. Secondly, it investigates the impact of the reliability of the monitoring system on the asset management modelling results. With the aid of the developed model, the number of repair actions and probability distributions of blade condition discovery time are obtained. In addition, the PN gives an indication of how misreporting (underestimation and overestimation) occurs and the extent of the misreporting. The simulation results illustrate the degree of uncertainty introduced into the monitoring results by the reliability of the monitoring system and, consequently, the extent to which this factor influences the maintenance strategies. The proposed model can be used to support asset management decisions when monitoring system performance degrades.

Comparison of applied loads on horizontal axis wind turbine blades using an open-source software Qblade and CFD solver ANSYS-FLUENT

Comparison of applied loads on horizontal axis wind turbine blades using an open-source software Qblade and CFD solver ANSYS-FLUENT

Feasibility and environmental assessment of introducing waste polyurethane from wind turbine blades as a modifier for asphalt

Recycled glass fibers from wind turbine blades have significant potential for enhancing the performance of asphalt mixtures. However, the impact of residual polyurethane (PU) components on asphalt performance remains uncertain, presenting a challenge to the high-value utilization of wind turbine blades in pavement engineering. This study investigates the effects of waste polyurethane (WPU) on the rheological properties and compatibility of SBS modified asphalt, widely used in pavement engineering under various temperature conditions. Molecular dynamics (MD) simulations were employed to analyze the underlying mechanisms. The results reveal that incorporating WPU improves the rutting factor and creep recovery rate of SBS modified asphalt, demonstrating superior high-temperature performance compared to SBS modified asphalt alone. The synergistic effect of WPU and SBS significantly enhances low-temperature crack resistance and overall asphalt compatibility. Additionally, the interaction between SBS and the four components of asphalt is strengthened, and diffusion mobility is reduced due to WPU incorporation. This indicates that WPU promotes a more compact structure and a higher relative concentration of SBS and the four components within the spatial system, thereby enhancing the stability of the WPU/SBS modified asphalt system. Furthermore, using WPU in asphalt mixtures not only avoids environmental pollution compared to traditional disposal methods but also offers considerable long-term economic benefits. Overall, WPU positively impacts the rheological properties and compatibility of SBS-modified asphalt, suggesting that processed wind turbine blades can be a viable solution for enhancing asphalt mixture performance.

An Improved YOLOv7 Model for Surface Damage Detection on Wind Turbine Blades Based on Low-Quality UAV Images

The efficient damage detection of the wind turbine blade (WTB), the core part of the wind power, is very improtant to wind power. In this paper, an improved YOLOv7 model is designed to enhance the performance of surface damage detection on WTBs based on the low-quality unmanned aerial vehicle (UAV) images. (1) An efficient channel attention (ECA) module is imbeded, which makes the network more sensitive to damage to decrease the false detection and missing detection caused by the low-quality image. (2) A DownSampling module is introduced to retain key feature information to enhance the detection speed and accuracy which are restricted by low-quality images with large amounts of redundant information. (3) The Multiple attributes Intersection over Union (MIoU) is applied to improve the inaccurate detection location and detection size of the damage region. (4) The dynamic group convolution shuffle transformer (DGST) is developed to improve the ability to comprehensively capture the contours, textures and potential damage information. Compared with YOLOv7, YOLOv8l, YOLOv9e and YOLOv10x, this experiment’s results show that the improved YOLOv7 has the optimal detection performance synthetically considering the detection accuracy, the detection speed and the robustness.

Recent advances in VAWT aerodynamic performance research: Optimal design

Vertical axis wind turbine is a popular research direction in recent years, and its aerodynamic performance directly affects its power generation efficiency. Using CFD method simulation, the aerodynamic characteristics of wind turbine blades can be deeply analyzed. In this paper, the numerical simulation progress of the aerodynamic performance of vertical axis wind turbines with airfoil as the main object in recent years is studied, the influence of different design parameters on the performance of wind turbines is discussed, the characteristics of current research are summarized, and the future research trends are prospected.

Pyrolysis process and products characteristics of glass fiber reinforced epoxy resin from waste wind turbine blades

The installed wind power capacity has reached up to 906 GW globally meaning the usage of wind turbine blades (WTBs) with around 9.06 Mt. The waste WTBs with a rapid growth was estimated to be 72.0 kt in 2022 based on the projected lifetime of 20 years. The recycling of fibers reinforced thermoset polymer from waste WTBs has become a knotty environmental issue. This work aimed at studying the pyrolysis behaviors of a glass fibers reinforced epoxy resin materials from a waste WTBs, and revealing the impacts of pyrolysis atmosphere and temperature on the pyrolysis products. It was found that the black glass fibers with deposited carbon and the clean glass fibers were obtained by pyrolysis in N2 and air, respectively. Both pyrolysis in N2 and air produced the pyrolysis oil and gas with similar compositions. The preferable strength of fibers and yield of oil could be obtained at applicable pyrolysis temperature of 450 °C. The oil yields were 13.17 wt.-% and 11.93 wt.-% by pyrolyzing at 450 °C in N2 and air, respectively. The analysis of pyrolysis pathway suggested that the oxygen promoted the decomposition of epoxy resin into small molecules of gases by pyrolysis in air. The utilization of recycled products gas was also discussed. The findings of this work could provide some suggestions to explore a route with low cost to recycling the waste WTBs by pyrolysis.

Characterization of composite materials with recycled wind turbine blade additives using atomic force microscopy

ABSTRACT The European Union’s efforts to increase the share of renewable energy translate into a growing number of wind farms. Post-operation wind turbines become increasing waste. Recycling wind turbine blades is a challenge due to the materials used (composites) and high costs. The article examines the influence of recyclate from wind turbine blades (derived from mechanical recycling) on the image of topography and Lateral Force Microscopy (LFM) in atomic force microscopy (AFM). Upon adding the recycled material, an increase in surface roughness is observed despite its prior polishing. The Young’s modulus determined from force spectroscopy (AFM mode) indicated a small difference in values between the matrix and reinforcement areas. This proves the significant influence of the primary and secondary interphase on the properties of secondary composites, which is an area for further research.

Selective production of phenol from the end-of-life wind turbine blade through catalytic pyrolysis

This study employed catalytic pyrolysis to enhance the selectivity and yield of phenol in the pyrolysis oil derived from the end-of-life wind turbine blade (WTB). It was confirmed that the NiO(10)/Al2O3 catalyst exhibited the best activity, reaching a phenol selectivity of 28.57 % at 500 °C with a heating rate of 10 °C/min. Furthermore, a competitive phenomenon between the catalytic formation of phenol and that of gaseous products was observed. Characterization results indicated that at lower loading content of NiO on the Al2O3 carrier, NiAl2O4 crystals tended to form preferentially, which reduced catalyst activity by covering surface strong acid sites. With increasing the loading content of NiO, saturation of NiAl2O4 formation occurred, and free NiO crystals became dominant. This resulted in the creation of abundant Lewis acid sites, enhancing the catalytic formation of phenol. Whilst, excessive accumulation of free NiO crystals increased strong acid sites and significantly generated lattice oxygen, promoting the cracking of pyrolysis oil to gaseous products, which was detrimental to phenol enrichment but facilitated the production of H2-rich syngas. The conclusions offered valuable insights for upgrading pyrolysis products derived from epoxy resin polymers during the recovery of end-of-life WTB.

Vibration control of the straight bladed vertical axis wind turbine structure using the leading-edge protuberanced blades

This study investigates the impact of structural responses resulting from alterations in aerodynamic characteristics caused by incorporating leading-edge protuberance (LEP) blades in vertical-axis wind turbines (VAWTs) under various wind speeds. The current experimental investigation was conducted on a scaled-down straight-blade VAWT with multiple wind speeds at a fixed pitch angle and uniform blade configuration. The unsteady structural excitation caused by the decay of vortices due to the different aerodynamic loads and its effect on the VAWT structure is examined in great detail. The presence of counter-rotating vortices from the LEP profile, however, enhances the aerodynamics of the blades at higher angles of attack. It is crucial to understand the structural characteristics resulting from changes in aerodynamics. The paper presents the effects of the LEP on the structural excitation of the VAWT by analyzing the acceleration and displacement data obtained from the static structure of VAWT for various operational wind speeds. The results showed decreased acceleration and displacement amplitudes for the VAWT with LEP at medium and higher wind speeds. Significant aerodynamic and structural damping was observed in the VAWT with LEP blades. The results obtained were in close agreement with the time and frequency domains of the measured displacement and acceleration from the structure. The bidirectional vibration control was observed for the VAWT with LEP, which was found to have a reduction ratio of 70 %.

Forecasting wind turbine blade waste with material composition and geographical distribution: Methodology and application to Germany

Wind energy has become a key player in global electricity generation. The management of end-of-life (EoL) wind turbine blade (WTB) material streams is a challenge that requires urgent attention. The aim of this study was to forecast the future EoL WTB material, composition and geographical distribution of decommissioned on- and offshore wind turbines in Germany. Based on the German core energy market data register and a review of forecasting methods, a hybrid approach was developed that combines a statistical, deterministic and stochastic model with three scenarios to assume the service life of wind turbines in operation. This method was applied to Germany to estimate the mass of WTBs until 2050. The results show that a total EoL WTB material mass of 698 kt is expected, consisting of 492 kt of glass fibre reinforced polymer WTBs and 206 kt of hybrid WTB material with a carbon fibre reinforced polymer mass share of approximately 12.4 kt. From 2024 onwards, a displacement of 64.4 km in the centre of gravity of the expected EoL WTB material stream towards the north-west coast of Germany could be observed. The authors demonstrate the novelty of the method and findings in relation to circular economy paths of EoL WTB material.

Mechanism of eccentricity influence on 3-DOF aerodynamic stability: New insights into instability evolution, energy harvesting, and vibration control

The inconsistency of mass center and elastic center, i.e., eccentricity, widely exists in various engineering structures and components, including iced conductors, wind turbine blades, airfoils, and cable-supported bridges, and can also be extended to the application of energy harvesting and vibration control. Although the eccentricity influence on aerodynamic stability has already been recognized as important, the underlying mechanism remains rather unclear. This study established a comprehensive framework of explicit eigenvalue solutions, offering in-depth insights into the aerodynamic stability mechanism in a vertical-horizontal-torsional 3-degree-of-freedom linear system under all possible frequency scenarios. These solutions elucidated the coupling mechanism of eccentricity, aerodynamic damping, aerodynamic stiffness, and structural frequencies. Remarkably straightforward criteria to predict the promoting/suppressing effect of eccentricity were proposed, consisting of eccentric angle and aerodynamic forces, which not only align with the traditional principles but also offer a broader application range in terms of structure types and wind speeds. Validations of the proposed solutions were performed for all frequency cases via numerical studies. For instability tendency evaluation, numerical studies on a thin plate showed that eccentricity has a significant impact due to the strong aerodynamic effect and large ratio of width/gyration radius, highlighting the importance of considering small eccentricity errors during experiments. Examination for energy harvesting revealed that a small eccentricity can dramatically enhance power generation efficiency, and the explicit solutions successfully explained the rules governing performance changes against frequency ratio, mass center position, rotation center position, etc. The analysis of a bundled conductor showed that the double pendulum can control galloping because it diminishes the eccentricity effect by shifting the eccentric angle. The proposed explicit solution framework provides a systematic view and new insights into the aerodynamic instability mechanism influenced by eccentricity, serving as a reference for the design and studies of various engineering structures, energy harvesting, and vibration control.

Aerodynamic efficiency assessment of a cross-axis wind turbine integrated with an offshore deflector

The present work examines the performance of an offshore cross-axis wind turbine (CAWT) with a flow deflector by integrating numerical and analytical methods. The deflector's geometry redirects flow in all directions, causing it to exit vertically and collide with the wind turbine's horizontal blades. In contrast, the blades of a vertical axis wind turbine (VAWT) harness the power of horizontal wind flow. The total power absorbed by the horizontal and vertical turbine blades represents the power of CAWT. In this study, the speed of the outflow from the deflector was initially determined through numerical simulation. The numerical simulation output was then utilized as an input for analytical Double Multiple Stream Tube (DMST) and Blade Element Momentum (BEM) methods to evaluate the vertical and horizontal turbine blades, respectively. This approach reduces the overall simulation time and establishes an offline coupling between analytical and numerical approaches. The findings of this research have unveiled a promising future for offshore wind energy generation. Through the implementation of a modeled deflector on a Cross-Axis Wind Turbine (CAWT), the power output reached a remarkable 19 KW with a power coefficient of 0.35 at an 8.4 m/s wind speed. The results indicate that the CAWT with the deflector produced a power output 35 % higher and was 45 % more efficient than a single Vertical-Axis Wind Turbine (VAWT). These outcomes illustrate the potential for greater energy production and efficiency in offshore wind farms.

Active Diagnostic Experimentation on Wind Turbine Blades with Vibration Measurements and Analysis

Abstract This paper deals with the key operational problems of wind turbosets, especially offshore, where vibrations are generated by rotor blades, as a consequence of erosive wear or icing. The primary causes of the imbalance of wind turbine rotors have been characterised, the observable symptoms of which include various forms of vibrations, transmitted from the turbine wheel to the bearing nodes of the power train components. Their identification was the result of an active diagnostic experiment, which actually entered the aerodynamic-mass imbalance of a turbine rotor into a wind power train, built as a small scale model. The recording of the observed monitoring parameters (vibration, aerodynamic, mechanical and electrical) made it possible to determine a set of symptoms (syndrome) of the deteriorated (entered) dynamic state of the entire wind turboset. This provides the basis for positive verification of the assumed concept and methodology of diagnostic testing, the constructed laboratory station and the measuring equipment used. For this reason, testing continued, taking into account the known and recognisable faults that most often occur during the operation of offshore wind turbosets. Transferring the results of this type of model research to full-size, real objects makes it possible to detect secondary (fatigue) damage to the elements transmitting torque from the wind turbine rotor to the generator early, especially the thrust bearings or gear wheel teeth.

The application of chromatographic methods in optimization and the enhancement of the oxidative liquefaction process to wind turbine blade recycling

AbstractThe concept of the circular economy aims to maximise the longevity of raw materials, materials, and final goods while simultaneously minimising waste generation. In order to accomplish this objective, researchers are currently exploring emission-free recycling methods and advancing a novel oxidative liquefaction methodology. This process is employed to efficiently degrade the polymer matrix which we can find among other things in wind turbine blades while also conducting chromatographic investigations of the resulting degraded resins. The conducted experiments included a temperature range spanning from 250 °C to 350 °C. The residence lengths varied from 30 to 90 min, while the pressures ranged from 20 to 40 bars. Additionally, the waste-to-liquid ratios were within the range of 5–25%, and the oxidant concentrations were between 15 and 45% by weight. The study’s results will help improve the design of the experiments by focusing on getting the highest concentrations of oxygenated chemical compounds, such as volatile fatty acids, aromatic hydrocarbons, and aromatic carboxylic acids. These compounds are the main chemicals obtained during resin degradation, and identifying the optimal conditions for their production will facilitate the implementation of this process on a larger scale. Graphic abstract

Wind Turbine Blade Fault Diagnosis: Approximate Entropy as a Tool to Detect Erosion and Mass Imbalance

Wind energy is a clean, sustainable, and renewable source. It is receiving a large amount of attention from governments and energy companies worldwide as it plays a significant role as an alternative source of energy in reducing carbon emissions. However, due to long-term operation in reduced and difficult weather conditions, wind turbine blades are always seriously damaged. Hence, damage detection in blade structure is essential to evaluate its operational condition and ensure its structural integrity and safety. We aim to use fractal, entropy, and chaos concepts as descriptors for the diagnosis of wind turbine blade condition. They are, respectively, estimated by the correlation dimension, approximate entropy, and the Lyapunov exponent. Formal statistical tests are performed to check how they are different across wind turbine blade conditions. The experimental results follow. First, the correlation dimension is not able to distinguish between all conditions of wind turbine blades. Second, approximate entropy is suitable to distinguish between healthy and erosion conditions and between healthy and mass imbalance conditions. Third, chaos is not a discriminative feature to distinguish between wind turbine blade conditions. Fourth, wind turbine blades with either erosion or mass imbalance exhibit less irregularity in their respective signals than healthy wind turbine blades.

The Study of Structural Dynamic Response of Wind Turbine Blades under Different Inflow Conditions for the Novel Variable-Pitch Wind Turbine

The Study of Structural Dynamic Response of Wind Turbine Blades under Different Inflow Conditions for the Novel Variable-Pitch Wind Turbine