Wind Turbine Blade Model Research Articles

Stress analysis of composite wind turbine blade by finite element method

In this study, the finite element analysis software ANSYS was used to analyze the composite wind turbine blade. The wind turbine blade model used is adopted from the 5 MW model of US National Renewable Energy Laboratory (NREL). The wind turbine blade is a sandwich structure, comprising outermost carbon fiber cloth/epoxy composites, the inner glass fiber/vinylester layers, and PVC foam core, together with stiffeners. The wind pressure is converted into the load on the blade structure. The stress distribution and deformation of wind turbine blade were obtained by considering different pitch angles and at different angular positions. The Tsai-Hill criterion was used to determine the failure of wind turbine blade. The results show that at the 0° pitch angle, the wind turbine blade is subjected to the largest combined load and therefore the stress is the largest; with the increasing pitch angle, the load gradually decreases and the stress is also smaller. The stress and displacement are the greatest when the wind blade is located at 120° angular position from its highest vertex.

Stress Analysis of Composite Wind Turbine Blade with Different Stacking Angle and Different Skin Thickness

Wind turbine blade is the most important part of wind turbine; most of the blades are made from composite materials. The 5 MW wind turbine blade model used in this study is adopted from US National Renewable Energy Laboratory (NREL). The finite element software ANSYS was used to analyze the stress distribution and deformation of wind turbine blade under various loads. The wind turbine blade is a sandwich structure made by carbon fiber cloth/epoxy composites as the outermost layer and the glass fiber/vinylester as inner layers, together with PVC foam as the core material. The composite stacking angle and skin thickness of wind blade were varied in the analysis. Four stacking angles in glass fiber/vinylester composites, [0 / 15 / 90 ] n n n s ± , [0 / 30 / 90 ] n n n s ± , [0 / 45 / 90 ] n n n s ± and [0 / 60 / 90 ] n n n s ± , were studied. The results show that the composite blade with [0 / 60 / 90 ] n n n s ± stacking angle in glass fiber/vinylester composites had a minimum stress and displacement. When varying the skin thickness of wind blade, both linear and optimal skin thicknesses can enhance the rigidity of blade, though increasing the weight of blade.

Active Flow Control of a Low Reynolds Number S809 Wind Turbine Blade Model under Dynamic Pitching Maneuvers

A low Reynolds number wind turbine blade model based on the S809 airfoil was tested in a subsonic wind tunnel to study the structural vibration of the blade under dynamic pitching maneuvers. Piezoelectric-based synthetic jet actuators were embedded inside the blade and activated with a synthetic jet momentum coefficient, Cμ of 2.30 × 10-3. Structural vibration was quantified for a range of unsteady angles undergoing “pitch up and down” and “sinusoidal pitch” maneuvers at a Reynolds number of 5.28 × 104. The blade tip deflection amplitude and frequency were acquired utilizing a pair of strain gauges mounted at the root of the model. Using active flow control vibration reduction was more effective during the pitch up portion of the blade motion cycle compared to the pitch down portion. This effect is due to dynamic stall, where a leading edge vortex is shed during the pitch up motion and contributes to higher lift compared to static angles of attack and lower lift when the blade is pitched down. Dynamic stall was measured with phase-locked stereoscopic particle image velocimetry (SPIV), where global mean flow measurements reveal a shift in location and reduction in the size of a recirculating flow structure near the suction surface of the blade during the pitch up motion compared to the pitch down.

Manufacturing technology of integrated textile-based sensor networks for in situ monitoring applications of composite wind turbine blades

Based on in situ strain sensors consisting of piezo-resistive carbon filament yarns (CFYs), which have been successfully integrated into textile reinforcement structures during their textile-technological manufacturing process, a continuous load of fibre-reinforced plastic (FRP) components has been realised. These sensors are also suitable for structural health monitoring (SHM) applications. The two-dimensional sensor layout is made feasible by the usage of a modular warp yarn path manipulation unit. Using a functional model of a small wind turbine blade in thermoset composite design, the sensor function for basic SHM applications (e.g. static load monitoring) are demonstrated. Any mechanical loads along the pressure or suction side of the wind turbine blade can be measured and calculated via a correlative change in resistance of the CFYs within the textile reinforcement plies. Performing quasi-static load tests on both tensile specimen and full-scale wind turbine blade, elementary results have been obtained concerning electro-mechanical behaviour and spatial resolution of global and even local static stresses according to the CFY sensor integration length. This paper demonstrates the great potential of textile-based and textile-technological integrated sensors in reinforcement structures for future SHM applications of FRPs.

Numerical simulation analysis as a tool to identify areas of weakness in a turbine wind-blade and solutions for their reinforcement

Offshore wind energy is one of the main sources of renewable energy that can benefit from new generation materials that exhibit good oxidation resistance and mechanical reliability. Composite materials are the best consideration for harsh environment and deep sea wind turbine manufacturing. In this study, a numerical simulation was implemented to predict the stress distribution over a wind turbine-blade and to determine areas with high stress concentration. Finite Element Analysis (FEA) was used to find optimal material and bonding techniques to construct the blade. By using Abaqus commercial software, a finite element model of wind turbine blade was analyzed under bending-torsion coupled with a static-load condition in flap-wise direction. Structural damage in critical zones varies according to ply orientation and stack thickness as a result of composite orthotropic nature. This study leads existing scenarios and techniques which would provide a new and better solutions for wind turbine blade designers. The root section and trailing edge were found to be critical zones in the wind turbine blade. The root section failure can be reduced by (1) adjusting the thickness of the structure or increasing the number of plies in the composites laminate stacking and by (2) adjusting the bonding technique to prevent trailing-edge failure. Transverse-stitch method and the carbon cord tying methods are most effective for trailing edge reinforcement. Both solutions are proposed to reduce failures in wind turbine blades and proven by step-by-step numerical study. The goal of this study is to deliver a good reference for wind turbine blade designers and to improve the accuracy during design phase as well as to avoid failure.

The Performance & Flow Visualization Studies of Three dimensional (3-D) Wind Turbine Blade Models

<p>The researches on the design of 3-D wind turbine blades have been received less attention so far even though 3-D blade products are widely sold. In the opposite, advanced researches in 3-D helicopter blade have been studied rigorously. Researches in wind turbine blade modeling are mostly assumed that blade span wise sections behaves as independent two dimensional (2-D) airfoils, implying that there is no exchange of momentum in the span wise direction. Further more flow visualization experiments are infrequently conducted.</p><p>The purpose of this study is to investigate the performance of 3-D wind turbine blade models with backward-forward swept and verify the flow patterns using flow visualization. In this research, the blade models are constructed based on the twist and chord distributions following Schmitz’s formula. Forward and backward swept are added to the wind turbine blades. It is hoped that the additional swept would enhance or diminish outward flow disturbance or stall development propagation on the span wise blade surfaces to give better blade design.</p><p>The performance of the 3-D wind turbine system models are measured by a torque meter, employing Prony’s braking system, and the 3-D flow patterns around the rotating blade models are investigated applying “tuft-visualization technique”, to study the appearance of laminar, separated and boundary layer flow patterns surrounding the 3-dimentional blade system.</p>For low speed wind turbines, Dumitrescu and Cardos (2011) have identified that stall spreads from the root of the rotating blade. In this study, it is found that for blades with (i) forward swept tip and backward swept root, the initial stall at the blade bottom would be amplified by concurrent strengthening flow due to the backward swept root to create strong stall spreading outward, and therefore the blades gives lower performance. For blades with (ii) backward swept tip and forward swept root, the initial stall at the blade bottom would be weakened by opposite weakening flow due to the forward swept root, generate weak stall that tend to deteriorate. These blades have better performance.

Modal-based damage identification for the nonlinear model of modern wind turbine blade

In this paper, the modal-based indices are used in damage identification of the wind turbine blade. In contrast of many of previous researches, the geometric nonlinearity due to the large structural deformation of the modern wind turbines blade is considered. In the first step, the finite element model (FEM) of the rotating blade is solved to obtain the modal features of the deformed structure under operational aerodynamic loading. Next, the accuracy and efficiency of the various modal-based damage indices including the frequency, mode shape, curvature of mode shape, modal assurance, modal strain energy (MSE) and the difference of indices (between the intact and damaged blades) are investigated. To adapt the MSE index calculation in nonlinear modeling, a new approach is introduced to include the effects of the structural nonlinearity. Furthermore, the effect of the damage length, its location and severity and also the effect of rotational speed and amplitude of loading are studied. The generic 5-MW NREL blade is used for the simulation study. The results show enough sensitivity of the mode shape curvature and MSE indices to the local damages. Moreover, the importance of geometric nonlinearity in the damage detection of the modern wind turbines is demonstrated.

Experimental damage detection in a wind turbine blade model using principal components of response correlation functions

The utilization of vibration signals for structural damage detection (SDD) is appealing due to the strong theoretical foundation of such approaches, ease of data acquisition and processing efficiency. Different methods are available for defining damage sensitive features (DSFs) based on vibrations, such as modal analysis or time series methods. The present paper proposes the use of partial autocorrelation coefficients of acceleration responses as DSFs. Principal component (PC) analysis is used to transform the initial DSFs to scores. The resulting scores from the healthy and damaged states are used to select the PCs which are most sensitive to damage. These are then used for making decisions about the structural state by means of statistical hypothesis testing conducted on the scores. The approach is applied to experiments with a laboratory scale wind turbine blade (WTB) made of glass-fibre reinforced epoxy composite. Damage is non-destructively simulated by attaching small masses and the WTB is excited with the help of an electrodynamic shaker using band-limited white noise. The SDD results for the selected subsets of PCs show a clear improvement of the detectability of early damages compared to other DSF selections.

Integrative Manufacturing of Textile-Based Sensors for Spatially Resolved Structural Health Monitoring Tasks of Large-Scaled Composite Components

For the continuous and non-destructive structural health monitoring (SHM) of fiber reinforced plastics (FRP), a one-step integration of one-or two-dimensional strain sensors based on piezo-resistive carbon filament yarns (CFY) into textile reinforced structures of subsequent FRP components has been realized during textile-technological manufacturing processes. The two-dimensional alignment of the sensor layouts is realized by a special process-integrated warp yarn path manipulation (WPM). With suchlike manufactured semi-finished reinforcement structures, a functional model of a small wind turbine blade in glass-fiber thermoset composite design has been build up. Using the CFYs’ piezo-resistive effect, mechanical strains can be measured and visualized due to a correlative change of the carbon filaments resistance. Performing quasi-static load tests on the blade and additional test specimens, comprehensible results of the electro-mechanical behavior and spatially resolving capacity of different sensor integration lengths have been achieved. The performed tests demonstrate, that global and even local mechanical stresses within complex FRP components can be measured spatially resolved using the approach of textile technologically integrated textile sensors.

The role of free stream turbulence with large integral scale on the aerodynamic performance of an experimental low Reynolds number S809 wind turbine blade

Effects of free stream turbulence with large integral scale on the aerodynamic performance of an S809 airfoil-based wind turbine blade at low Reynolds number are studied using wind tunnel experiments. The case of wind turbine blades subjected to turbulence structures with large integral scale is of interest since in the atmospheric boundary layer very large-scale structures interact with the blades. A constant chord (2-D) S809 airfoil wind turbine blade model with an operating Reynolds number of 2.08×105 based on chord length was tested for a range of angles of attack representative of fully attached and stalled flow as encountered in typical wind turbine operation. The smooth-surface blade was subjected to a quasi-laminar free stream with very low free-stream turbulence as well as to elevated free-stream turbulence generated by an active grid. This turbulence contained large-scale eddies with levels of free-stream turbulence intensity of up to 6.14% and an integral length scale of about 60% of chord-length. The pressure distribution was acquired using static pressure taps and the lift was subsequently computed by numerical integration. The wake velocity deficit was measured utilizing hot-wire anemometry to compute the drag coefficient also via integration. In addition, the mean flow was quantified using 2-D particle image velocimetry (PIV) over the suction surface of the blade. Results indicate that turbulence, even with very large-scale eddies comparable in size to the chord-length, significantly improves the aerodynamic performance of the blade by increasing the lift coefficient and overall lift-to-drag ratio, L/D for all angles tested except 0°.

Evaluating the fidelity and robustness of calibrated numerical model predictions

Purpose – Numerical models are being increasingly relied upon to evaluate wind turbine performance by simulating phenomena that are infeasible to measure experimentally. These numerical models, however, require a large number of input parameters that often need to be calibrated against available experiments. Owing to the unavoidable scarcity of experiments and inherent uncertainties in measurements, this calibration process may yield non-unique solutions, i.e. multiple sets of parameters may reproduce the available experiments with similar fidelity. The purpose of this paper is to study the trade-off between fidelity to measurements and the robustness of this fidelity to uncertainty in calibrated input parameters. Design/methodology/approach – Here, fidelity is defined as the ability of the model to reproduce measurements and robustness is defined as the allowable variation in the input parameters with which the model maintains a predefined level of threshold fidelity. These two vital attributes of model predictiveness are evaluated in the development of a simplified finite element beam model of the CX-100 wind turbine blade. Findings – Findings of this study show that calibrating the input parameters of a numerical model with the sole objective of improving fidelity to available measurements degrades the robustness of model predictions at both tested and untested settings. A more optimal model may be obtained by calibration methods considering both fidelity and robustness. Multi-criteria Decision Making further confirms the conclusion that the optimal model performance is achieved by maintaining a balance between fidelity and robustness during calibration. Originality/value – Current methods for model calibration focus solely on fidelity while the authors focus on the trade-off between fidelity and robustness.

Novel structural modeling and mesh moving techniques for advanced fluid–structure interaction simulation of wind turbines

SummaryIn this paper, we target more advanced fluid–structure interaction (FSI) simulations of wind turbines than reported previously. For this, we illustrate how the recent advances in isogeometric analysis of thin structures may be used for efficient structural mechanics modeling of full wind turbine structures, including tower, nacelle, and blades. We consider both horizontal axis and vertical axis wind turbine designs. We enhance the sliding–interface formulation of aerodynamics, previously developed to handle flows about mechanical components in relative motion such as rotor–tower interaction to allow nonstationary sliding interfaces. To accommodate the nonstationary sliding interfaces, we propose a new mesh moving technique and present its mathematical formulation. The numerical examples include structural mechanics verification for the new offshore wind turbine blade design, FSI simulation of a horizontal axis wind turbine undergoing yawing motion as it turns into the wind and FSI simulation of a vertical axis wind turbine. The FSI simulations are performed at full scale and using realistic wind conditions and rotor speeds. Copyright © 2014 John Wiley & Sons, Ltd.

The Modeling and Stress Analysis of Wind Turbine Blade

With the development of wind power generation technology, the wind turbine blade is becoming more and more important. Modeling and stress analysis of the wind turbine blade are very critical for the further design and the application of wind turbine blade. The small-scale wind turbine blade was focused on, considering the glass fiber reinforced plastic material. Based on the parameters of airfoil and the geometrical parameters of blade, the three-dimension model of blade was established with the modeling software. Then the model was introduced into ANSYS software to carry out the FEM analysis. According to the displacement solution of blade, the maximal displacement occurs in the blade tip while working, but it is less than the safety displacement of wind turbine. And the stress concentration occurs in the center of the blade, which corresponds to the comprehensive stress from the elastic stress solution of the wind turbine blade.Last, it can be found that the thermal stress does not play a major role from the thermal stress solution. The FEM results were compared with the tensile strength of the material and the safe displacement. Therefore, the effectiveness of FEM model and real safety of blade were verified. DOI : http://dx.doi.org/10.11591/telkomnika.v12i6.5536

Determination of three-dimensional movement for rotary blades using digital image correlation

Non-contact and accurate motion measurement of the rotary objects is crucial in engineering applications. A modified Newton–Raphson algorithm, which is capable of positioning marks with large rotation, has been proposed. A stereo imaging system with a pair of synchronized digital high-speed cameras was developed and achieved full-field displacement measurement based on 3D image correlation photogrammetry for rotary objects. This system has been applied to measuring the 3D motion of a wind turbine blade model. The displacement components of the rotary blade were presented, and the corresponding frequency spectra were investigated. The experimental results demonstrated that the proposed system could measure the 3D motion of rotary blades precisely, and it also provided an alternative potential non-contact diagnosis means for large wind turbine blades.

IEC 61400-2에 의거한 소형 풍력발전용 블레이드 축소모델의 단순 하중 계산 및 구조 시험

This study deals with simplified load calculation and structural testing for scale down model of small wind turbine blade. First, the blade was designed and produced scale down to 0.2 ratio of initial blade. And moments were acquired by simplified load calculation equations according to IEC 61400-2 standard. Also, structural test using weight was conducted to obtain the maximum moment. Therefore maximum moments were compared at calculation and test.

Parameterized Modeling and Analysis of Wind Turbine Blade Using VB and ANSYS

It is very difficult to establish a model of wind turbine blade in finite element software directly because of complexity of the shape. To solve this problem, parameterized modeling and analysis program of wind turbine blade is developed applying of ANSYS secondary development technique based on VB6.0. Processes of establishing a finite element model, applying loads and extracting Post-processing data of wind turbine blade are described. A numeral example demonstrates the program is feasible and correct. The research work can help to speed up application of ANSYS secondary technique in design and analysis of wind turbine blade and provide references for parameterized modeling and analysis of similar engineering in the future.

Dynamic Analysis for Wind Turbine Composite Blade

Wind turbine blade model is analyzed based on finite element method. Research and comparison of blade natural frequencies is made in different rotational working conditions taking into account external factors such as the rotational inertia force. Also the relationship between the composite ply angle and natural frequency is analyzed. The result shows that the nature frequency of wind turbine blade is influence greatly by the stress stiffening effect for the blade rotation. And the nature frequency of wind turbine blade can be designed by adjusting the single fiber layer ply angle of blade.

Impeller modeling and analysis based on UG NX/KF and fluent

Parametric modeling of the impeller which drove a small wind device was built by knowledge fusion technology. NACA2410 airfoil blade was created by KF language. Using technology of UG/KF secondary development for the automatic modeling of wind turbine blade, the program can read in the airfoil data files automatically and the impeller model entity can be generated automatically. In order to modify the model, the aerodynamic characteristics of the impeller were analyzed for getting aerodynamic parameters by Fluent. The maximum force torch and best parameters of impeller were calculated. A physical prototype impeller was manufactured and the correctness of the design was verified, and the error of force torch between simulation and experimental results is about 10%. Parameterization design of the impeller model greatly improves the efficiency of modeling and flexibility of the CAD system.

Aerodynamic Optimization of Variable Pitch Wind Turbine Blade Based on Adaptive Genetic Algorithm

Take maximum power output of blade element as design target, establish a optimization model of variable pitch wind turbine blade. Using the adaptive genetic algorithm to search for to overcome the shortcomings of early maturity and poor stability, it can reach more close to the global optimum than the classical genetic algorithm. Use this method to design a 3MW variable pitch wind turbine blade, the results show that this optimization model is correct and the method is practical.

A Continuum Based Three-Dimensional Modeling of Wind Turbine Blades

Accurate modeling of large wind turbine blades is an extremely challenging problem. This is due to their tremendous geometric complexity and the turbulent and unpredictable conditions in which they operate. In this paper, a continuum based three dimensional finite element model of an elastic wind turbine blade is derived using the absolute nodal coordinates formulation (ANCF). This formulation is very suitable for modeling of large-deformation, large-rotation structures like wind turbine blades. An efficient model of six thin plate elements is proposed for such blades with non-uniform, and twisted nature. Furthermore, a mapping procedure to construct the ANCF model of NACA (National Advisory Committee for Aeronautics) wind turbine blades airfoils is established to mesh the geometry of a real turbine blade. The complex shape of such blades is approximated using an absolute nodal coordinate thin plate element, to take the blades tapering and twist into account. Three numerical examples are presented to show the transient response of the wind turbine blades due to gravitational/aerodynamics forces. The simulation results are compared with those obtained using ANSYS code with a good agreement.