•Effects of wakes on the film cooling for a turbine blade with laid-back fan-shaped holes are illustrated.•Effects of mass flux ratios on the film cooling effectiveness are illustrated.•The film ...cooling effectiveness at low and high free-stream turbulence intensity are analyzed.•The combined effects of unsteady wake and free-stream turbulence are analyzed.•Detailed film cooling effectiveness distributions are obtained using PSP technique.
Detailed film cooling effectiveness distribution for a gas turbine blade under the effects of unsteady wakes and oncoming free-stream turbulence intensities was obtained using pressure sensitive paint (PSP) technique. Tests were performed on a linear cascade at Reynolds number of 3.85 × 105 based on the blade chord at cascade exit. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The test blade has three rows of compound angled cylindrical film holes at the leading edge, five rows of laid-back fan-shaped holes on the pressure surface and three rows of laid-back fan-shaped holes on the suction surface. The wake Strouhal number was varied from 0 to 0.36 and three mass flux ratios were determined. The oncoming free-stream turbulence intensities are 2.7% and 26.9%, respectively. Results show that the effect of the mass flux ratio on the film cooling effectiveness decreases under the high turbulence intensity and unsteady wake conditions. In most regions of the blade surface, the film cooling effectiveness decreases with the increase of wake Strouhal number, and the free-stream turbulence superimposed on the unsteady wake reduces the film cooling effectiveness further. The effect of the unsteady wake decreases under the high free-stream turbulence conditions.
Abstract The Miriti Palm (Mauritia flexuosa) grows abundantly in the Amazon Region of Brazil. The petiole (PMP) that supports the leaves, has a density of about one-half of Balsa wood (BW), which is ...used in the manufacture of wind turbine blades. A further possible advantage of PMP is that harvesting does not kill the palm tree, in contrast to the harvesting of BW. Because the mechanical properties of PMP have not been measured, we determined the shear and tensile properties of 16 samples of PMP and BW to allow a preliminary assessment of PMP as a possible material for blades. The absolute shear and tensile strengths for BW are higher, but specific properties (normalized by the density) are similar and can favour PMP. Direct substitution of BW by PMP would reduce the weight of a typical large blade by around 2%.
Abstract CFD-based shape design is a state-of-the-art approach in wind energy that can lead to novel shape features. High computation costs have, however, until now hindered a widespread use of the ...approach. To address this issue, this work investigates two ways to enhance a CFD-based design framework, using a shape study of wind turbine blade tips as a test case. First, a quantification of the speed-up factor (× 3.6) achieved through so-called tailored meshes is presented. Then, a comparison of mesh adaptation strategies is given, further speeding up the procedure (× 2.3). The combined speed-up factor reaches above 8, showing that CFD-based shape design procedures may indeed be accelerated using tailored meshes and a correct mesh adaptation strategy.
Abstract Tenon-jointed turbine blades will be impacted by airflow and centrifugal force during the high-speed rotation of the engine. The surface contact stiffness of the tenon and tenon groove will ...change with complex external loads. Through the analysis of the micro-morphological characteristics of the contact surface of the tenon joint bladed disk, the contact characteristics of the asperities on the rough surface are determined. At the same time, to solve the problem that the traditional microscopic contact stiffness calculation formula cannot be applied to the tangential displacement load, the periodic piecewise tangential stiffness expression is derived based on external loads of the normal force and the equivalent tangential force. Furthermore, this paper studies the properties of the tangential stiffness curves under different external load frequency ratios and phase differences. An increase in the frequency ratio will decrease the step value of the piecewise function and make it tend to a smooth transition. The change of the phase difference will directly change the monotonicity and fluctuation of the stiffness curve. The macro and micro theoretical analysis methods of contact characteristics have been established.
As the global demand for wind power continues to increase, there is growing concern about the disposal of waste wind turbine blades, which are predominantly composed of glass fiber-reinforced polymer ...composites. This review provides an overview of recent advancements in the recovery of glass fibers from waste wind turbines, examining various recycling techniques including mechanical recycling, pyrolysis, combustion, and chemical solvolysis. Additionally, the review assesses the impact of each technique on the properties of the recovered glass fibers and explores potential secondary applications for these fibers. Notably, the review emphasizes the significant impact of recycling methods on the characteristics of recovered glass fibers and establishes meaningful connections among recycling approaches, fiber properties, and potential applications. Furthermore, the review offers insights into future research directions and technological advancements needed to address current challenges in this field. The objective of this review is to advance knowledge and technology for addressing waste wind turbine blades and promoting the sustainable utilization of recovered glass fibers.
•Several methods for recovering glass fibers from waste turbine blades are outlined.•Recycling methods strongly affect the properties of recovered glass fibers.•Pyrolysis and chemical solvolysis are currently the two most promising methods.•Relations of recycling methods, fiber features, and potential reuses are obtained.•The reutilization of recovered fibers needs to break free from traditional fields.
An image recognition model based on a deep learning network is proposed for the automatic extraction of image features and the accurate and efficient detection of wind turbine blade damage. The Otsu ...threshold segmentation method is used to segment the blade image to eliminate the influence of the image background on the detection task. In order to improve the recognition performance of the proposed deep learning model, transfer learning and an ensemble learning classifier are used in a convolutional neural network model. Transfer learning is used to enhance the ability of the proposed model to extract abstract features and accelerate the convergence efficiency, whereas the random forest-based ensemble learning classifier is used to improve the accuracy of detecting the blade defects. The performance of the proposed model is verified by using unmanned aerial vehicle (UAV) images of the wind turbine blades. The proposed model provided better performance than the support vector machine (SVM) method, the basic deep learning model and the deep learning model combined with the ensemble learning approach.
•A new method of blade damage detection based on deep learning is proposed.•Transfer learning and ensemble learning classifier are used in the proposed model.•The proposed model can detect damage automatically and nondestructively by images.
With the increasing size of wind turbines in terms of their dimensions and capacity, structural design optimization for their blades is becoming all the more important. This study suggests an ...improved optimization framework. Blade optimization is performed in two stages: the ply lay-up pattern of the spar cap in the initial blade configuration based on the existing configuration, followed by the cross-sectional design optimization at several spanwise locations. The genetic algorithm is adopted and, in terms of the structural integrity evaluation, the final configuration results are found to be safe; in addition, the number of plies in the spar cap rapidly decreases through the two-stage design optimization procedure. As a result, the blade is lighter, and the lighter blade also reduces the applied load on the wind turbine. This will have an excellent effect that leads to a reduction in the weight of the entire turbine system.
•Impact between the blade root and hub during an offshore mating task is studied.•The sideways impact between the guiding connection and hub is found critical.•Impact load causes severe bending and ...plastic deformation of the guide pin bolt.•Excessive bending of guide pin triggers the failure of the adjacent root laminate.•Guidelines are provided to aid onboard decision making after the impact events.•The study aims to derive response-based operational limits for the mating task.
Single-blade installation is a popular method for installing blades on bottom-fixed offshore wind turbines. A jack-up crane vessel is often employed, and individual blades with their roots equipped with mechanical joints and bolted connections are lifted to the tower-top height and mated with a pre-assembled hub. The final mating phase is challenging and faces significant risks of impact. Due to relative motions between the blade and the hub, substantial impact forces may arise and lead to severe structural damages at root connections, thereby causing delays in the installation task. The present paper considers a realistic scenario of the mating process and investigates the consequences of such impact loads. Here, a single-blade model with tugger lines and a monopile model were established using a multi-body formulation, and relative velocities under collinear wave and wind conditions were obtained. A three-dimensional finite element model was developed for the blade root with T-bolt connections, and an impact investigation was performed for the case in which a guiding connection impacts the hub. The results show severe bending and plastic deformation of the guide pin bolt together with failure of the adjoining composite laminate at the root connection. Based on the type of damage obtained for the different environmental conditions considered, this paper also discusses its consequence on the installation tasks and suggests onboard decision making in case of an impact incident. The results of this study provide new insights regarding the mating phase and can be utilised to establish response-based operational limits.
•The failure of aluminized turbine blade is mainly induced by the cracking at the interface.•Evident cross-sectional delamination develops on the turbine blade surface after ...aluminizing.•Interdiffusion zone is formed by the mutual diffusions of Al and alloying elements.•Large amount of directional penetrations of σ phases in the substrate diffusion zone.•Interaction of pores, carbides and σ phases leads to the interfacial cracking of aluminized blades.
The service damage mechanism of K403 Ni-based superalloy turbine blade with the aluminized coating are investigated systematically. Fracture morphologies are inspected with a failure event, and the microscopic damage mechanisms are explored based on the aluminized blades with different operation times. It concludes that the formation of massive pores, aggregation of bulk carbides, coarsening and breaking of σ phases, development of continuous γ′ film, etc, lead to the multi-source fatigue cracking at the interface, with the grain boundaries and Kirkendall non-contact areas as the propagation channels, resulting in the rapid fatigue failure and significant life reduction of aluminized turbine blades.
•Machine learning based condition monitoring is proposed for wind turbine blade.•Crack, Erosion, Loose connection, Pitch angle twist and Bend faults are considered.•Histogram features were extracted ...from the vibration signals.•Feature classification was performed using different machine learning classifiers.•Locally weighted learning shows the better result of 93.83%.
The main objective of the proposed research study is to discriminate different blade fault conditions which affect the wind turbine blades under operating condition through machine learning approach. A three bladed wind turbine was chosen and the faults like blade bend, blade cracks, blade erosion, hub-blade loose connection and pitch angle twist were considered in the study. This problem is formulated as a machine learning problem which consists of three phases, namely feature extraction, feature selection and feature classification. Histogram features were extracted from vibration signals and feature selection was carried out using J48 decision tree algorithm. Feature classification was performed using lazy classifiers like nearest neighbour, k-nearest neighbours, locally weighted learning and K-star classifier. The results of these classifiers were compared with respect to their correctly classified instances (accuracy percentage) and found that, locally weighted learning yielded a maximum accuracy of 93.83% with a computational time of 0.07 s.
PDF
