Wind Turbine Blade Model Research Articles

One-way fluid–structure interaction modeling and multi-objective optimization of horizontal-axis wind turbine blades equipped with winglets

ABSTRACT This study aims to investigate the effects of backward-directed winglets applied on the NREL Phase-II reference wind turbine geometry on structural and aerodynamic characteristics and to reveal optimized configurations. The aerodynamic pressure distributions on the blades were imposed as boundary conditions for the FEM analyses since the structural characteristics of the turbine were analyzed by adopting a one-way Fluid Structure Interaction (FSI) approach. The Taguchi analysis with an L27 orthogonal array revealed the descending order of importance of design variables on the coefficient of power ( C P ): height, cant angle, toe angle, curvature radius, and finally twist angle. For von-Mises stress, the descending order of importance is height, cant angle, toe angle, twist angle, and curvature radius. A multi-objective genetic algorithm using artificial neural network (ANN) models was used to optimize the objectives C P and von-Mises stress. Pareto-optimal solutions with off-design points were obtained, and their performances were compared to the reference NREL Phase-II geometry. As a result, it was observed that there was an increase in C P from 8.07% to 15.56% and the von-Mises stress showed a considerable increase up to 231.13%. The study demonstrates the aerodynamic benefits and structural drawbacks of various winglet designs in horizontal axis wind turbines.

Surface profile inspection for large structures with laser scanning

Fringe projection profilometry is a powerful tool that is widely applied to shape measurement of objects in engineering. Limited by the light intensity of the projection unit, this technique is difficult to be applied to surface inspection of large structures, especially in outdoor applications. In this study, a line laser source is selected as the light projection unit. The line laser beam is controlled to scan the surface with the predefined angular speed while a stationary imaging unit captures images. An image fusion strategy has been proposed to construct grating images with a constant phase shift, which facilitates full-field phase shifting in determination of the structural profile. The accuracy of the measurement method is discussed and compared with a commercial 3D laser scanner. The proposed technique has also been applied to the surface topography of the wind turbine blades. The experimental results show that the bulging defects on the surface of the wind turbine blade model are detectable, which shows the feasibility of the proposed method in characterization of surface profile on large structures.

Identification of Damage in a Wind Turbine Blade Using Mechanical Measurements and Artificial Neural Networks

Due to the stochastic nature of environmental loadings, a lot of interest is paid in the discovery of possible damages to the involved equipment in modern industry. In wind turbines' blades, the development of a smart structural health monitoring system is essential. In this paper, a large-scale composite wind turbine blade model is designed and used for the detection of several damage scenarios. The process is mainly based on the development of monitoring techniques that exploit the capabilities of artificial neural networks. These techniques can provide the exact position of possible damages, under given external loading scenarios. Moreover, the use -of such methods decreases significantly the need for external intervention and at the same time it increases the accuracy of the whole approach. The above processes are simulated using the finite element method. The goal is to develop a neural network that realizes the correlation of measurements with damage patterns. The goal is focused on the solution of inverse problems involving elastically deformable structures, based on remote mechanical measurements. The correlation between measurements and damages, which is much more complicated in comparison to image analysis, is studied by means of neural networks.

Building blocks towards progressive fatigue damage modeling of a whole wind turbine blade

This paper presents a concise summary of the recent fatigue damage modeling research in the Mechanics of Materials and Structures (MMS) research group at Ghent University, which utilizes physics-based models and microscopic experiments to develop components for a progressive fatigue damage model of laminated composite structures. The paper discusses the evolution of ply cracking and delamination under cyclic loading and highlights distinct modeling elements for stress analysis and fatigue damage evolution characterization. It also explores the experiments required for model calibration and validation, including the use of digital image correlation to quantify damage mechanisms. Additionally, the paper discusses the use of neural networks for efficient and robust modeling of damage effects and outlines the remaining steps required to develop a comprehensive fatigue design tool. Finally, the recent developments with the BladeMesher software of the research group provide a platform to integrate this fatigue design tool for complete wind turbine blades.

Comparative Study on Vibration Characteristics of Biaxial Carbon/Glass Hybrid Wind Turbine Blades

Endeavor to investigate the effect of carbon/glass hybrid ratio on blade flutter vibration characteristics. Based on the theory of strength of materials, the influence of carbon/glass hybrid ratio on the tensile strength of the sample under concentrated load was analyzed experimentally. The 10 KW wind turbine blade model was taken as the research object, and different carbon/glass hybrid ratios (2:6, 4:4, and 6:2) were selected as the blade reinforcement materials. The blade vibration characteristics were analyzed from three aspects: deformation displacement, blade mode, and stress distribution. The results showed that the blade hybrid ratio was between 6:2 and 4:4, and the maximum improvement in tensile performance was achieved. The hybrid ratios of 4:4 and 6:2 significantly improved the deformation resistance of the blades and required a shorter time to reach equilibrium. The blade stress was mainly concentrated at 1/3 of the blade, which was one of the main reasons for the phenomenon of blade waving.

Economic competitiveness of pultruded fiber composites for wind turbine applications

Pultrusion manufacturing of fiber reinforced polymers has been shown to yield some of the highest mechanical properties for unidirectional composites, having a high degree of fiber alignment with consistent performance. Pultrusions offer a low-cost manufacturing approach for producing unidirectional composites with a constant cross-section and are used in many applications, including spar caps of wind turbine blades. However, as an intermediate processing step for wind blades, the additional cost of manufacturing pultrusions must be accompanied by sufficient increases in mechanical performance and system benefits. Wind turbine blades are manufactured using vacuum-assisted resin transfer molding with infused unidirectional fiberglass or carbon pultrusions for the spar cap. Infused fiberglass composites are among the most cost-effective structural materials available and replacing this material in the cost-driven wind industry has proven challenging, where infused fiberglass spar caps are still the predominant material system in use. To evaluate alternative material systems in a pultruded composite form, it is necessary to understand the costs for this additional manufacturing step which are shown to add 33%–55% on top of the material costs. A pultrusion cost model has been developed and used to quantify cost sensitivities to various processing parameters. The mechanical performance for pultruded composites is improved versus resin-infusion manufacturing with a 17% increase in design strength at a constant fiber volume fraction, but also enables higher achievable fiber volume fractions. The cost-specific mechanical performance is compared as a function of processing parameters for pultruded composites to identify the opportunities for alternative material and manufacturing approaches for wind turbine spar caps. Four materials are compared in a representative wind turbine blade model to assess the performance of pultruded carbon fiber systems and pultruded fiberglass relative to infused fiberglass, where the pultruded systems produce lower weight blades with various cost distinctions.

Application of Green’s function in frequency solution for wind turbine blade modelled as box beam

In order to study the vibration of composite wind turbine blades, a Green’s function method for frequency calculation is proposed. Based on the variational asymptotic method and Hamilton principle, the mechanical model of wind turbine blade, modelled as box beam with composite laminated structure, is established by using circumferential asymmetric stiffness design. The Green function method is used to analyze the frequency of wind turbine blades from the aspect of ply angle, and the numerical examples are compared with other calculation methods. The results show that the Green function method has good accuracy.

Research on 3D Modeling and Dynamic characteristics of wind turbine blade

In order to prevent blade resonance, reduce blade deflection, improve wind turbine power generation efficiency and wind energy utilization rate, the blade model of 3 kW wind turbine is established, and the natural frequency of wind turbine blade is analyzed. Based on the vibration theory, the effects of dynamic stiffening and rotational softening on the natural frequencies of blades are analyzed. Study the change rule of blade vibration mode under rotating speed of 0~300rpm, and analyze the influence of two effects on blade frequency. The results show that at low speed, the rotating softening effect of the blade is obvious, and the vibration frequency decreases; At high speed, the stress stiffening effect is more obvious, the vibration frequency increases, and the coupling vibration has greater destructiveness.

Numerical Modeling and Analysis of a Horizontal Axis RM1 NACA-4415 Wind Turbine

Wind turbines are widely used for conversion of the wind power into mechanical energy. The failure of the blade during operation is a common phenomenon which can lead to the degradation of the power output. Modeling and analysis of wind turbine blade is critical for the design and safe and efficient operation. In this study, a one-way coupled Finite Element (FE) scale model of RM1 SAFL turbine is developed to simulate structural integrity and deformations in the blades. The study is primarily focusses on the strength and deformation of the blades under varying wind speeds ranging from 5 m/s to 30 m/s. The wind turbine blades were modelled from aluminum alloy and unidirectional carbon reinforced composite (epoxy carbon). The results obtained from numerical simulation demonstrated higher stresses and blade tip deformation in blades from composite compared to aluminum AL 6061 alloy. Maximum displacements were calculated at the tip of blades and were well under the threshold level. The maximum stress intensity was found in the center of the blades. On the basis of the current geometry, modal analysis of turbine blades was performed and benchmark cases for the dynamic response were investigated. The natural frequency for aluminum alloy was calculated to be almost three time higher than of composite material structure. The modal in case of composite material was approximately 35% of that obtained using aluminum alloy. This study suggests further analysis to predict surface integrity of the turbine blades under more volatile wind conditions

A correction method for large deflections of cantilever beams with a modal approach

Abstract. Modal-based reduced-order models are preferred for modeling structures due to their computational efficiency in engineering problems. One of the important limitations of the classic modal approaches is that they are geometrically linear. This study proposes a fast correction method to account for geometric nonlinearities which stem from large deflections in cantilever beams. The method relies on pre-computed correction terms and thus adds negligibly small extra computational efforts during the time domain response analyses. The accuracy of the method is examined on a straight-beam model and International Energy Agency (IEA) 15 MW wind turbine blade model. The results show that the proposed method increases the accuracy of modal approaches significantly in secondary deflections due to nonlinearities such as axial and torsional motions for the two studied cases.

DESIGN OPTIMIZATION OF SMALL WIND TURBINE BLADE BASED ON STRUCTURAL AND FATIGUE LIFE ANALYSES

In this paper, the horizontal axis wind turbine (HAWT) blade model with a power of 5 kW and a length of 2.5 m was designed using MATLAB code based on the blade element momentum theory (BEMT) method. The Finite Element Method was used to simulate and validate the blade of wind turbine under normal and extreme operating wind load conditions to compute the deflections. The approach of the standard IEC 61400.2 was applied to obtain the fatigue loads, estimate damage, and predict the life of the blade. After analyzing the results of the Finite Element model for the studied E-glass MY 750 under the influence of normal operating winds, it was found that there is an optimization in the deflection of the flapwise by 11% and the deflection of the trailing and leading-edge by 31%. A great agreement was also obtained between the results of the FEM compared with the case H of SLM operating in extreme winds condition. The fatigue life of the wind turbine blade was also studied and it was found that the fiberglass material will not work more than 0.1 years by the SLM method and 4.18 years by the aeroelastic method (FAST software). Finally, it was found by the SLM method the studied blade of 5 kW will have a design life of 20 years if it is made of carbon fiber material.

An investigation of the Steady-State and Fatigue Problems of a Small Wind Turbine Blade Based on the Interactive Design Approach

A wind turbine blade is an essential system of wind energy production. During the operation of the blade, it is subjected to loads resulting from the impact of the wind on the surface of the blade. This leads to appear large deflections and high fatigue stresses in the structure of blades. In this paper, a 5 kW horizontal axis wind turbine blade model is designed and optimized using a new MATLAB code based on blade element momentum (BEM) theory.The aerodynamic shape of the blade has been improved compared with the initial design, the wind turbine power has been increased by 7% and the power coefficient has been increased by 8%. The finite Element Method was used to calculate the loads applied to the blade based on Computational Fluid Dynamics (CFD) and BEM theory.High agreements were obtained between the results of both approaches (CFD and BEM).The ANSYS software was also used to simulate and optimize the structure of the blade by applying variable static loads 3.3, 6, and 8.3 kg and compared the results with the experimental results. It was reduced the maximum deflectionswith 37%, 42.85%, and 42.61% when using CFRP material and 4.5%, 15.45%, and 16.19% for GFRP material that corresponds to the applied forces. Based on the results, the mass of the optimized model decreased by 47.86% for GFRP and 71.24% for CFRP. IEC 61400.2 standard was used to estimate thefatigue loads, damage, blade life prediction, and verify blade safety usinga Simplified Load Model(SLM) and FAST software. It was found that the blade will be safe under extreme wind loads, and the lifetime of the wind blade (GFRP) is 5.5 years and 10.25 years,according to SLM and FAST software, respectively. At the same time, the lifetime of the wind blade (CFRP)is more than 20 years, according to the two applied methods.

Research on fatigue performance of offshore wind turbine blade with basalt fiber bionic plate

As a new type of inorganic green and high performance fiber material, basalt fiber has broad application prospects in the field of offshore wind power. In order to promote the application of basalt fiber in offshore wind turbine blade, the static tensile test and tensile-tensile fatigue test of basalt fiber reinforced polymer (BFRP) at different stress levels were carried out to obtain the elastic modulus, tensile strength, and SN curve of BFRP. The equivalent model of basalt fiber bionic plate and the finite element model of wind turbine blade were established by Ansys Workbench software. Based on nCode software, the fatigue performance of the offshore wind turbine blade with basalt fiber bionic plate was analyzed and its fatigue life was predicted. The results show that the elastic modulus of BFRP is more than 2.5 times that of glass fiber reinforced polymer (GFRP), and BFRP has good plastic energy dissipation capacity. The equivalent model based on equivalent plate theory is suitable for static and dynamic analysis of basalt fiber bionic plate. The fatigue damage of the wind turbine blade under low wind speed is mainly concentrated in the edge of the blade root, the area where the skin and the web intersect and near the tip of the blade. Under the high wind speed, the fatigue damage covered the whole skin, only slight damage occurred at the trailing edge of the tip. The dangerous point is mainly located near the tip of 50 m–60 m along the span direction. The traditional Miner theory can accurately predict the fatigue life of wind turbine blade, and the fatigue life of the wind turbine blade with basalt fiber bionic plate is 29 years, while the fatigue life of the glass fiber wind turbine blade at the same scale is less than 1 year.

Performance Analysis of PLA Material Based Micro-Turbines for Low Wind Speed Applications.

Various studies have been conducted in recent years to find solutions to the issues in wind energy conversion systems. A 100W horizontal axis micro wind turbine is built for low wind speed applications in this work. The Blade Element Momentum theory approach was used to design the 100W micro wind turbine blade. The wind turbine blade 3D model was created using the CREO CAD 3.0 software. Based on the aerodynamic studies, the airfoil S9000 is chosen among others for generating high power at low wind speed. The density, Young’s modulus, and the Poisson ratio of the proposed wind turbine blade model with acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) materials were compared. ABS and PLA materials were investigated using a 0.33 mm layer of infill ranging from 10% to 100%. PLA and ABS output values were compared in terms of deformation, equivalent stress, and equivalent strain. PLA materials, on the other hand, have less deformation and greater structural properties than ABS materials. The wind blade structural analysis was performed in ANSYS 15 software, and the details of experimental and simulated results are presented in this paper.

An examination of hub wind turbine utilizing fluid-structure interaction strategy

A compromise approach between aerodynamic performance and structural robustness is presented. The modeling of horizontal axis wind turbine blade GE1.5-XLE is studied regarding the applicability of three different solution methods computational fluid dynamics (CFD), one – way (unidirectional), and two – way (bidirectional) coupling fluid – structure interaction (FSI) at a shedding frequency of the vortex far from the natural frequency. The predicted results showed significant differences between the unidirectional coupling solution and experimental data. While, the bidirectional coupling method proposed accurate FSI and gave results closer to the experimental measurements than unidirectional simulation results. The bidirectional coupled approach appears to be more stable and accurate, where a large number of time steps should be used for uncoupled method to achieve the same level of precision. For the present case involving large blade strain, the difference between the prediction of rigid blade solution using CFD and FSI model increases considerably. However, it is concluded that for large blade strains, the FSI model is closer shown to be more adequate for accurate representation of the turbine performance. Moreover, when optimization is a key aspect, bidirectional simulations should be performed regardless of the higher computational cost.

CFD Modeling of Wind Turbine Blades with Eroded Leading Edge

The present work compares 2D and 3D CFD modeling of wind turbine blades to define reduced-order models of eroded leading edge arrangements. In particular, following an extensive validation campaign of the adopted numerical models, an initially qualitative comparison is carried out on the 2D and 3D flow fields by looking at turbulent kinetic energy color maps. Promising similarities push the analysis to consequent quantitative comparisons. Thus, the differences and shared points between pressure, friction coefficients, and polar diagrams of the 3D blade and the simplified eroded 2D setup are highlighted. The analysis revealed that the inviscid characteristics of the system (i.e., pressure field and lift coefficients) are precisely described by the reduced-order 2D setup. On the other hand, discrepancies in the wall friction and the drag coefficients are systematically observed with the 2D model consistently underestimating the drag contribution by around 17% and triggering flow separation over different streamwise locations. Nevertheless, the proposed 2D model is very accurate in dealing with the more significant aerodynamics performance of the blade and 30 times faster than the 3D assessment in providing the same information. Therefore the proposed 2D CFD setup is of fundamental importance for use in a digital twin of any physical wind turbine with the aim of carefully and accurately planning maintenance, also accounting for leading edge erosion.

An innovative aerodynamic design methodology of wind turbine blade models for wind tunnel real-time hybrid tests based on genetic algorithm

The physical model tests of floating offshore wind turbines (FOWTs) in wave basins cannot simulate the aerodynamic loads accurately. The real-time hybrid model test in wind tunnel provided a better solution to this problem, especially for the simulation of unsteady aerodynamic behaviors. The key to wind tunnel test is the design of aerodynamic thrust-matched blade model. In this paper, an innovative methodology was proposed to design the wind turbine blade models for the wind tunnel tests, based on the genetic algorithm. The design was focused on the aerodynamic thrust performance of blade model to achieve equivalent aerodynamic thrust under different wind speeds. To prove the applicability of this methodology, the DTU 10 MW and NREL 5 MW wind turbine were used for case study and the low-Reynolds airfoil SD7032 was chosen for the aerodynamic design. During the design process, three shape control methods were employed for the twist angles and chords of blades and the effects of these three methods were also compared. The aerodynamic performances of blade models were verified using Aerodyn of FAST, compared to the prototypes. According to the results, the aerodynamic thrust performances of blade models reached good agreement with prototypes in the full wind speed range.

Nonlinear dynamic characteristics of horizontal-axis wind turbine blades including pre-twist

This paper focuses on the dynamic modeling and vibration analysis of horizontal axis wind turbine (HAWT) blades with emphasis on the effects of the pre-twist, rotational rigid body motion and coupling among the different blade's degrees of freedom. The blade is considered as a rotating pre-twisted beam mounted on a rigid hub with a constant angle relative to the plane of rotation, so-called precone angle. Kinetic energy of the blade based on its elastic as well as rigid motion together with its strain energy and generalized forces resulting from gravitational, centrifugal and aerodynamic loadings are obtained and used to derive new coupled dynamic equations by means of Hamilton's principle. The weak formulation is constructed and the Rayleigh-Ritz method (RRM) is adopted to extract a reduced order model (ROM) for the blade's vibration analysis. The developed nonlinear ROM is linearized around the steady-state solution and the blade's dynamic characteristics are obtained. The reference wind turbine blade called NREL 5-MW HAWT blade is selected as the case-study and effects of pre-twist, centrifugal force, angular velocity-depended terms, nonlinearities and transverse static loads on its dynamic characteristics are investigated. Results are shown to be in good agreement with available data in the literature.

Comparative study of static and fatigue performances of wind turbine blade materials

Climate impact has been one of the emerging issues currently leading to severe environmental impacts such as rising sea levels and droughts. One viable way to address these increasing global issues such as climate change, pollution, and global warming is by switching over to renewable energy. Past research studies have suggested that increasing wind energy capacity by two orders of magnitude would be an ideal way to accomplish this minimization of climatic crises. The efficiency of the wind energy industry solely depends on the blades, as it is the structure that limits the performance and lifetime of the turbine. Therefore, proper choice of material selection for wind turbine blades is an important factor. The primary objectives of this research study were to identify and propose a suitable material for wind turbine blades, create a 3D model to compare the proposed material with existing material, and testing of the material using static and fatigue studies. As a solution, natural fiber/S-glass and natural-fiber/Carbon fiber hybrid composites were proposed as new reinforcing material along with a polypropylene polymer as the matrix material. A proposed 3D model of a horizontal wind turbine blade was created using SolidWorks software and blade dimensions of an average 5 kW horizontal axis wind turbine. Static and fatigue tests were also performed on the blade to determine how the blade would perform when subjected to aerodynamic loads. To validate the results obtained, experimental runs were carried out with the aid of ANSYS software utilizing the same boundary conditions.

A comparison between aeroacoustic source mapping techniques for the characterisation of wind turbine blade models with microphone arrays

<p class="Abstract">Characterising the aeroacoustic noise sources generated by a rotating wind turbine blade provides useful information for tackling noise reduction of this mechanical system. In this context, microphone array measurements and acoustic source mapping techniques are powerful tools for the identification of aeroacoustic noise sources. This paper discusses a series of acoustic mapping strategies that can be exploited in this kind of applications. A single-blade rotor was tested in a semi-anechoic chamber using a circular microphone array. <br />The Virtual Rotating Array (VRA) approach, which transforms the signals acquired by the physical static array into signals of virtual microphones synchronously rotating with the blade, hence ensuring noise-source stationarity, was used to enable the use of frequency domain acoustic mapping techniques. A comparison among three different acoustic mapping methods is presented: Conventional Beamforming, CLEAN-SC and Covariance Matrix Fitting based on Iterative Re-weighted Least Squares and Bayesian approach. The latter demonstrated to provide the best results for the application and made it possible a detailed characterization of the noise sources generated by the rotating blade at different operating conditions.</p>