•Damage detection techniques for wind turbine blades are reviewed.•Detection principles, development methods, pros and cons of each technique are addressed.•Discussions on fault indicators for the ...aforementioned methods are presented.•Research prospects on damage detection techniques for wind turbine blades are given.
Blades play a vital role in wind turbine system performances. However, they are susceptible to damage arising from complex and irregular loading or even cause catastrophic collapse, and they are expensive to maintain. Defects or damages on wind turbine blades (WTBs) not only reduce the lifespan and power generation efficiency of the wind turbine, but also increase monitoring errors, safety risks and maintenance costs. Therefore, damage detection for WTBs is of great importance for failure avoidance, maintenance planning, and operation sustainability of wind turbines. This paper provides a comprehensive review of state-of-the-art damage detection techniques for WTBs, including most of those updated methods based on strain measurement, acoustic emission, ultrasound, vibration, thermography and machine vision. Firstly, typical damages of WTBs are comprehensively introduced. Secondly, detection principles, development methods, pros and cons of the aforementioned techniques for blade inspection, and their fault indicators are reviewed. Finally, potential research directions of WTB damage detection techniques are addressed via a comparative analysis, and conclusions are drawn. It is expected that this review will provide guidelines for practical WTB inspections, as well as research prospects for damage detection techniques.
Isogeometric analysis (IGA) has been a particularly impactful development in the realm of Kirchhoff–Love thin-shell analysis because the high-order basis functions employed naturally satisfy the ...requirement of C1 continuity. Still, engineering models of appreciable complexity, such as wind turbine blades, are typically modeled using multiple surface patches and, often, neither rotational continuity nor conforming discretization can be practically obtained at patch interfaces. A penalty approach for coupling adjacent patches is therefore presented. The proposed method imposes both displacement and rotational continuity and is applicable to either smooth or non-smooth interfaces and either matching or non-matching discretization. The penalty formulations require only a single, dimensionless penalty coefficient for both displacement and rotation coupling terms, alleviating the problem-dependent nature of the penalty parameters. Using this coupling methodology, numerous benchmark problems encapsulating a variety of analysis types, geometrical and material properties, and matching and non-matching interfaces are addressed. The coupling methodology produces consistently accurate results throughout all tests. Furthermore, the suggested penalty coefficient of α=103 is shown to be effective for the wide range of problem configurations addressed. Finally, a realistic wind turbine blade model, consisting of 27 patches and 51 coupling interfaces and having a chordwise- and spanwise-variant composite material definition, is subjected to buckling, vibration, and nonlinear deformation analyses using the proposed approach.
•Conduct a non-contact 3D Scanning Laser Doppler Vibrometer (SLDV) test on a three-bladed wind turbine assembly.•Develop a finite element model of the assembly including the composite blade ...modeling.•Correlate modal parameters and dynamic response between the SLDV test and the finite element model.•Investigate high-order complex curvature mode shapes and mode coupling of the wind turbine blade through both experimental and numerical approach.
Experimental and numerical modal analysis on wind turbine blades has been previously studied, considering mainly low order bending modes. However, high-order modes are also critical modes for understanding blade dynamics. The mode coupling is essential because a better understanding of the high-frequency blade dynamics can support advances in model validation, blade aeroelastic simulations, blade design, and structural health monitoring. However, these high-order modes and the associated mode couplings of wind turbine blades have not been studied. This work presents a comprehensive experimental and numerical study based on three modal tests and a correlated finite element simulation to study the complex curvature mode shapes and mode coupling dynamics for a three-bladed wind turbine assembly. Three tests are conducted: Test 1, ten accelerometers are deployed on the whole assembly under impact excitation; Test 2, nine accelerometers are deployed on a single blade under impact excitation; and Test 3, a non-contact 3D Scanning Laser Doppler Vibrometer (SLDV) test is performed on a single blade under shaker excitation. This is the first work to use a 3D SLDV for an experimental modal test on the wind turbine blade. With 300–400 points measured with the 3D SLDV, experimental mode shapes having a high spatial resolution with 3D response are used to characterize the coupling for the low-order and high-order modes with complex curvatures. A reliable finite element model of the three-bladed assembly, including the composite blade modeling, is also developed and is well correlated with Test 2 and Test 3. With the high-fidelity 3D SLDV test and well-correlated finite element model, this is also the first work of using experimental and numerical approaches to investigate the high-order mode shape with complex curvatures and mode coupling of bending and torsional behavior that is present in the wind turbine blade for these high-order modes.
In power and energy systems, both the aerodynamic performance and the structure reliability of turbine equipment are affected by utilized blades. In general, the design process of blade is high ...dimensional and nonlinear. Different coupled disciplines are also involved during this process. Moreover, unavoidable uncertainties are transported and accumulated between these coupled disciplines, which may cause turbine equipment to be unsafe. In this study, a saddlepoint approximation reliability analysis method is introduced and combined with collaborative optimization method to address the above challenge. During the above reliability analysis and design optimization process, surrogate models are utilized to alleviate the computational burden for uncertainties‐based multidisciplinary design and optimization problems. Smooth response surfaces of the performance of turbine blades are constructed instead of expensively time‐consuming simulations. A turbine blade design problem is solved here to validate the effectiveness and show the utilization of the given approach.
Vibration-based Structural Health Monitoring (SHM) techniques are among the most common approaches for structural damage identification. The presence of damage in structures may be identified by ...monitoring the changes in dynamic behavior subject to external loading, and is typically performed by using experimental modal analysis (EMA) or operational modal analysis (OMA). These tools for SHM normally require a limited number of physically attached transducers (e.g. accelerometers) in order to record the response of the structure for further analysis. Signal conditioners, wires, wireless receivers and a data acquisition system (DAQ) are also typical components of traditional sensing systems used in vibration-based SHM. However, instrumentation of lightweight structures with contact sensors such as accelerometers may induce mass-loading effects, and for large-scale structures, the instrumentation is labor intensive and time consuming. Achieving high spatial measurement resolution for a large-scale structure is not always feasible while working with traditional contact sensors, and there is also the potential for a lack of reliability associated with fixed contact sensors in outliving the life-span of the host structure. Among the state-of-the-art non-contact measurements, digital video cameras are able to rapidly collect high-density spatial information from structures remotely. In this paper, the subtle motions from recorded video (i.e. a sequence of images) are extracted by means of Phase-based Motion Estimation (PME) and the extracted information is used to conduct damage identification on a 2.3-m long Skystream® wind turbine blade (WTB). The PME and phased-based motion magnification approach estimates the structural motion from the captured sequence of images for both a baseline and damaged test cases on a wind turbine blade. Operational deflection shapes of the test articles are also quantified and compared for the baseline and damaged states. In addition, having proper lighting while working with high-speed cameras can be an issue, therefore image enhancement and contrast manipulation has also been performed to enhance the raw images. Ultimately, the extracted resonant frequencies and operational deflection shapes are used to detect the presence of damage, demonstrating the feasibility of implementing non-contact video measurements to perform realistic structural damage detection.
•Extends a novel acoustics-based damage detection approach for wind turbine blades.•Develops a unique wavelet algorithm for efficient denoising of damage signals.•Performs replicable simulation study ...to parameterize the wavelet algorithm.•Significantly enhances the performance of the acoustics-based damage detection technique.
The development of a viable structural health monitoring (SHM) technology for the operational condition monitoring of wind turbine blades is of great interest to the wind industry. In order for any SHM technology to achieve the technical readiness and performance required for an operational implementation, advanced signal processing algorithms need to be developed to adaptively remove noise and retain the underlying signals of interest that describe the damage-related information. The wavelet packet transform decomposes a measured time domain signal into a time-frequency representation enabling the removal of noise that may overlap with the signal of interest in time and/or frequency. However, the traditional technique suffers from several assumptions limiting its applicability in an operational SHM environment, where the noise conditions commonly exhibit erratic behavior. Furthermore, an exhaustive number of options exist when selecting the parameters used in the technique with limited guidelines that can help select the most appropriate options for a given application. Appropriately defining the technique tends to be a daunting task resulting in a general avoidance of the approach in the field of SHM.
This work outlines an adaptive wavelet packet denoising algorithm applicable to numerous SHM technologies including acoustics, vibrations, and acoustic emission. The algorithm incorporates a blend of non-traditional approaches for noise estimation, threshold selection, and threshold application to augment the denoising performance of real-time structural health monitoring measurements. Appropriate wavelet packet parameters are selected through a simulation considering the trade-off between signal to noise ratio improvement and amount of signal energy retained. The wavelet parameter simulation can be easily replicated to accommodate any SHM technology where the underlying signal of interest is known, as is the case in most active-based approaches including acoustic and wave-propagation techniques. The finalized adaptive wavelet packet algorithm is applied to a comprehensive dataset demonstrating an active acoustic damage detection approach on a ~46 m wind turbine blade. The quality of the measured data and the damage detection performance obtained from simple spectral filtering is compared with the proposed wavelet packet technique. It is shown that the damage detection performance is enhanced in all but one test case by as much as 60%, and the false detection rate is reduced. The approach and the subsequent results presented in this paper are expected to help enable advancement in the performance of several established SHM technologies and identifies the considered acoustics-based SHM approach as a noteworthy option for wind turbine blade structural health monitoring.
•Blade temperature difference in heat treatment is due to uneven energy absorption.•Adjusting turbine blade orientation can reduce shielding effect between blades.•Convert the actual heat treatment ...temperature problem into an optimization problem.•The optimized arrangement reduces blade temperature difference by nearly 50%.
Nickel-based single-crystal turbine blades are critical components of jet engines. Due to element segregation and microstructural defects in as-cast blades, vacuum heat treatment is essential. Controlling the blades’ heat treatment temperature is crucial for improving mechanical performance. However, when treating multiple blades simultaneously, large temperature differences often occur, making it challenging to ensure consistent and uniform temperatures. This paper establishes a numerical algorithm that links blade temperature with radiant energy, optimizing blade arrangement to achieve uniform energy distribution and temperature field homogenization. The improved view factor finite element algorithm is more suitable for blade structures. The Particle Swarm Optimization (PSO) and Coordinate Descent (CD) methods were used to solve the optimization function, aiming to minimize the temperature difference among blades. Finite element simulation was utilized to model the temperature field of the blades during radiative heat transfer from heating elements. The PSO and CD optimization methods were employed to find the local optimal solution that minimizes the view factor variance, reducing it from 2.24 before optimization to about 1. Simultaneously, the optimized maximum average temperature difference of the blades was 71.1 °C, approximately 50 % lower than the 138.8 °C before optimization. By comparing the view factor values with the simulated temperature fields, the strong correlation between the view factor and blade temperature was verified. This paper innovatively proposes a numerical method for optimizing blade arrangement to homogenize the temperature field, effectively enhancing temperature consistency during the heat treatment process.
The application of evolutionary algorithms to wind turbine blade design can be interesting, by reducing the number of aerodynamic-to-structural design loops in the conventional design process, hence ...reducing the design time and cost. Recent developments showed satisfactory results with this approach, mostly combining genetic algorithms with the blade element momentum theory. The general objective of the present work is to define and evaluate a design methodology for the rotor blade geometry in order to maximize the energy production of wind turbines and minimize the mass of the blade itself, using for that purpose stochastic multi-objective optimization methods. An optimization benchmark problem was proposed, which represents the wind conditions and present wind turbine concepts found in Brazil. A variable speed pitch-controlled 2.5 MW direct-drive synchronous generator turbine with a rotor diameter of 120 m was chosen as concept. Four different multi-objective evolutionary algorithms were selected for evaluation in solving this benchmark problem: Non-dominated Sorting Genetic Algorithm version II (NSGA-II), Quantum-inspired Multi-objective Evolutionary Algorithm (QMEA), Multi-objective Evolutionary Algorithm Based on Decomposition (MOEA/D), and Multi-objective Optimization Differential Evolution Algorithm (MODE). Detailed analysis of the best compromise blade design showed that the output of the design methodology is feasible for manufacturing.
•We give a formulation for the blade design geometry with rigorous math.•The resulting multiobjective problem is solved by means of different metaheuristics.•Results showed the approach's efficacy when applied to Brazilian wind conditions.
•This article expanded the range of rotating impingement cooling channel tests from Redj = 1 × 104 Ro = 0.2 to Redj = 5 × 104 Ro = 2.0.•Lower Re (Re ≤ 2 × 104) improves heat transfer with less drop. ...However, higher Re’s (Re > 2 × 104) turbulence lowers efficiency.•Nusselt number drops by 15.3 % at 0.25 rotational speed; optimal heat transfer at Z/D = 2 for Redj＜4.3 × 104, but effect lessens for Redj > 4.3 × 104. Higher Z/D enhances heat transfer but reduces uniformity.
To enhance the high-temperature capability of turbine blades and meet the requirements of advanced design, this research examines the intricate flow characteristics and the heat transfer occurring on the internal walls effects of leading-edge impingement cooling structures under different impingement distances. In this study, copper block method is employed for heat transfer testing, extending the testing range of rotating impingement cooling channels from Redj = 1 × 104, Ro = 0.2 to Redj = 5 × 104, Ro = 2.0. The findings reveal that the Nusselt number along the channel is significantly influenced by flow distribution and turbulence intensity. At lower Re (Re ≤ 2 × 104), the flow velocity increases along the channel due to the decrease in pressure drop, resulting in enhanced heat transfer. However, at higher Re (Re ＞ 2 × 104), increased flow rate leads to intensified turbulence and thickening of the boundary layer, consuming fluid energy and reducing the temperature difference, thereby adversely affecting heat exchange around the impingement holes. Moreover, Nu decreases with increasing rotation speed, with the highest average decrease of 15.3 % when Ro reaches 0.25. For cases where Redj ＜ 4.3 × 104, an impingement distance-to-diameter ratio (Z/D) = 2 exhibits optimal heat transfer performance. Conversely, when Redj＞4.3 × 104, the influence of impingement distance will diminish. Larger impingement distances increase the HTC but are accompanied by increased non-uniformity. Therefore, selecting an appropriate impingement distance can reduce boundary layer formation and flow separation, thereby forming an optimal flow structure, which contributes to promoting heat exchange and improving heat transfer uniformity. A correlation based on geometrical parameters has been proposed to predict the average Nusselt number for jet impingement arrays with varying geometrical configurations.
•Film cooling effectiveness on pressure surface with diffusion slot holes was experimentally investigated.•Diffusion slot hole provides better film cooling effectiveness than fan-shaped hole on ...pressure surface.•Large wall radius of concave surface and acceleration effect are beneficial to increase film cooling effectiveness.•Higher blowing ratio and density ratio produce greater cooling effectiveness of diffusion slot hole.
The film cooling effectiveness of diffusion slot hole was experimentally examined using pressure sensitive paint technique at a low-speed linear cascade. As a comparison, the film cooling effectiveness of fan-shaped hole was also measured. The mainstream Mach number at the cascade inlet and outlet was 0.1 and 0.19, respectively. The effects of blowing ratio, density ratio and hole location on the film cooling effectiveness were investigated. The experimental results demonstrated that the film cooling effectiveness of diffusion slot hole is obviously higher than that of fan-shaped hole. The difference of area-averaged effectiveness from surface arc length-to-hole diameter ratio of S/D = 1 to S/D = 30 between the two film hole schemes is maximum at first row, and the absolute increment is over 0.2 when the blowing ratio is larger than 1.0. The increase of blowing ratio elevates the film cooling effectiveness of the diffusion slot hole. Generally, the farther the film hole away from the blade leading edge, the higher the film cooling effectiveness. Meanwhile, the diffusion slot hole shows less sensitivity to film hole location compared to fan-shaped hole. In addition, the elevating density ratio leads to a positive influence on the film cooling effectiveness of diffusion slot hole.
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