Blade Deformation Research Articles

Experimental Investigation of the Dynamic Deformation of Wind Turbine Blades Based on 3D-Digital Image Correlation

A wind turbine is a rigid–flexible coupling system, and its blades will be deformed under the action of aerodynamic force, inertia force, and elastic force. To monitor the deformation of the blades, this paper builds a dynamic deformation measurement system for wind turbine blades based on 3D-DIC and directly measures the three-dimensional displacement distribution of different blades under different operating conditions to obtain the dynamic deformation of the blades. The experimental results show that the dynamic waving deformation of the blade shows the trend of increasing and then decreasing with the increase in wind turbine rotational speed and incoming wind speed, and when the rotational speed reaches 500 r/min and the incoming wind speed reaches 9 m/s, the blade deformation reaches the maximum value; the dynamic waving deformation of wind turbine blade decreases with the increase in the elastic modulus of the blade and the degree of the decrease decreases gradually; the dynamic deformation of is predicted by the multiple displacement distribution of different blades under different operating conditions, and is obtained by the fitting of the experimental data. This paper develops a 3D-DIC-based dynamic testing system for wind turbine blades, conducts experimental studies to verify and prove the practicality of the system, and finally obtains the prediction polynomials for the dynamic deformation of wind turbine blades under different operating conditions.

Data Acquisition System for a Hydroelectric Turbine with Deformable Blades

The scientific paper proposes a remote data transmission and acquisition system, for the analysis of the electrical parameters of a portable hydroelectric turbine with deformable blades placed on the stream. The major objective proposed by the authors is to monitor the transformation of the kinetic energy of water into electricity. Due to the impossibility of directly measuring the turbine elements as a whole, remote data transmission was chosen. This information is collected from the generator of the hydroelectric turbine through transducer elements into digital signals, is encoded and transmitted wirelessly to the receiver located on the shore, decoded, and then processed in real time and displayed on the monitor screen of a computer system in order to make decisions when the situation requires it. Data transmission is carried out in both directions (half duplex) through an efficient request/response communication protocol. Considering that the turbine is located in a hard-to-reach place, on the river, it was imposed to supply with reserve electric energy, autonomous from batteries, for the electronic part that is responsible for acquiring data from the hydroelectric generator. In this way, the monitoring circuit works permanently regardless of the turbine’s operating mode: normal or fault. The authors also present in detail the research methodology, the research results, the final conclusions resulting from the experimental data as well as the original contributions made through this applied research.

Aeroelastic Simulation of Full-Machine Wind Turbines Using a Two-Way Fluid-Structure Interaction Approach

Two-way fluid–structure interaction (FSI) simulation of wind turbines has gained significant attention in recent years due to the growth of offshore wind energy development. Strong coupling procedures in these simulations predict realistic behavior with higher accuracy but result in increased computational costs and potential numerical instabilities. This paper proposes a mixed weak and strong coupling approach for the FSI simulation of a 5 MW wind turbine. The deformation of the turbine blade is calculated using a weak coupling approach, ensuring blade deflection meets a convergence criterion before rotating to the next azimuthal position. Fluid and solid solvers are partitioned, utilizing the commercial software packages STAR-CCM+ and Abaqus, respectively. Flexible and rigid blade cases are modeled, and the calculated loads, power, and blade tip displacement for the rotor at a constant rotating speed are compared. The proposed model is validated, showing good agreement with the existing literature and results comparable to those from another validated wind turbine simulator. The effect of rotor–tower interaction is evident in the results. Based on our calculations, the power production of flexible blades is evaluated to be 9.6% lower than that of rigid blades.

Aerodynamic and structural optimization of wind turbine blade considering natural of frequencies of vibration

In recent years, wind energy has garnered significant global attention due to its immense energy and environmental potential, leading to a substantial increase in both capacity and size of wind turbines, evolving from a nominal power of 75kW to 7.5MW and a rotor diameter of 17m to over 125m. However, this scaling-up has introduced new challenges related to instability caused by the aeroelastic effect, which stems from the interplay between wind loads and the structural deformation of wind turbine blades. Consequently, an effective model necessitates well-defined aerodynamic and structural components. Yet, the complex geometric shapes of turbines demand extensive computational resources for analysis, particularly given their composite materials and intricate configurations.Various research institutions, including NREL, DTU, and ECN, have developed aeroelastic tools for wind turbine studies, integrating structural and aerodynamic modules. The prevalent approach employs the BEMT (Blade Element Moment Theory) model for aerodynamic simulation and FEM models for structural dynamic analysis. The BEMT model partitions the blade into elements to evaluate aerodynamic loads based on local characteristics. This amalgamation offers an efficient solution for predicting element performance parameters. Additionally, the BEM model provides a computationally economical alternative to more intricate models, making it a cost-effective choice for wind turbine analysis and a cheaper tool compared to robust methods, like CFD.This work proposes an aerodynamic optimization method constrained by the structural model, focusing on the natural vibration frequencies of wind turbine blades. The methodology comprises three phases: defining the aerodynamic model using the CCBlade code in Julia Language, implementing the structural analysis method via FEM for rotating Timoshenko beams in MATLAB, and integrating the aerodynamic and structural models on a multi-objective optimization platform. Evolutionary algorithms were employed to enhance wind turbine energetic efficiency and avoid structural instabilities within this study. By leveraging advancements in modeling and optimization techniques, the aim is to contribute to the development of more efficient and reliable wind turbines, further promoting the transition to clean and sustainable energy sources.

Characterization of Wind Turbine Blade Deformation and Wake Flow Field with Different Numbers of Lay-Up Layers

The change in the composite lay-up method affects the blade stiffness, which in turn affects the structural dynamic and aerodynamic characteristics, but the influence law is not yet clear. In this paper, two-way fluid–structure coupling is used to study wind turbine blades with different numbers of lay-up layers. The analysis results show the following: (1) With the increase in the number of pavement layers, the maximum deformation of the blade tip decreases, the magnitude of the decrease also decreases gradually, and the growth trend of deformation along the blade spreading direction is gradually flattened. (2) The maximum stress–strain of the root of the blade gradually decreases, the tip of the blade is the opposite of the blade, the unevenness of the distribution of the stress–strain of the surface of the blade is gradually slowed down, and the concentration area is shifted back. (3) The different numbers of pavement layers affect the turbulence intensity of the blade in the flow field space. Herein, the spatial distribution trend of turbulence intensity in the flow field of wind turbine blades with different numbers of layers is basically the same, and the trend of turbulence intensity changes is gentle when the number of layers is increased. (4) The amount of the tip vortex in the wake stream of the wind turbine decreases, and the decay rate of the center vortex increases. A reasonable lay-up scheme can improve the deformation and stress of the blade, extend the service life of the blade, promote airflow mixing, and enhance the energy conversion efficiency.

Fluid-structure interaction analysis of an elastic surface-piercing propellers

In high-speed planing craft, surface-piercing propellers (SPPs) operate semi-submerged in a two-phase air-water environment, facing stress and displacement from variable forces. In this paper, the fluid-structure interaction (FSI) of the SPP is investigated at immersion ratios of 30 %, 50 %, 70 % and 90 %, under low and high advance coefficients. A coupling of Reynolds-averaged Navier–Stokes equations (RANS) and elasticity theory are used to simulate fluid dynamics and the blade deformation with the multi-physics computational fluid dynamics software STAR-CCM+. The analysis is performed after several rotations of the SPPs at five different positions. The results show that at the advance coefficient of 0.4, a higher immersion ratio increases torque, thrust, efficiency, maximum stress, and maximum displacement. When the advance coefficient is equal to one, the efficiency, maximum stress, and maximum displacement remain constant for the immersion ratio above 50 %. The maximum displacement occurs at the blade tip, while maximum stress is at the trailing edge root. Most blade deformations happen where the blade enters the water, aligns perpendicularly with the water surface, and exits. The two-phase flow around the blade increases its displacement.

Laser-induced nano-Ag/graphene composites for highly responsive flexible strain sensors

In this focused on laser-induced nano-Ag/graphene composites were evaluated as an electrode layer for highly responsive flexible strain sensors. The dimension of Ag nanoparticles was adjusted using potassium hydroxide (KOH) at different concentrations. Moreover, the characteristics of laser-induced nano-Ag/graphene composites were examined by scanning electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. The performance of the proposed sensor was tested using a single-column universal test equipment combined with a precision electrical meter. The 6 M KOH nano-Ag/graphene-based strain sensor had large gauge factors of 23.1 under a micro-strain of 0.0042 % and 492.95 under a 16 % strain. Furthermore, the strain sensor under 10 cycles of stretching/releasing demonstrated excellent linearity, repeatability, and stability of response in different strain ranges of 1 % to 13 % at 2 % intervals. The sensor under 3 % and 5 % strain for 1000 cycles of stretching/releasing tests exhibited good stability and durability. The proposed sensor used to detect wind turbine blade deformation exhibited better response performance. The developed sensor holds a great application potential in real-time monitoring of the structural health of bridges and deformation of railway tracks, tracking human movement, identifying hill slides, assessing fatigue of mechanical components, etc.

Aeroacoustic Analysis of Rotor in Forward Flight Considering Blade Elastic Deformation

Abstract A rotor aeroacoustic calculation model of the rotor in forward flight based on CAMRAD II and FW-H equation was established, which can involve blade elastic deformation. CAMRAD II was used to calculate the actual motion of the blade and the rotor’s unsteady aerodynamic load based on the elastic blade model. The blade dynamics module in the noise calculation program was replaced to consider the blade elastic deformation in forward flight based on the FW-H equation. The forward flight noise characteristics of a full scale rotor were researched. The research shows that the rotor has obvious torsion and flap elastic deformation. The blade elastic deformation has little effect on the directivity of noise in forward flight. In the main noise propagation direction, blade deformation affects the loading noise, resulting in a maximum variation of 3.0dB or more in total noise. In noise calculation, the accuracy of noise prediction can be improved by matching the position of the real blade tip.

Studying and analysis of deformation and stresses in horizontal-axis wind turbine using fluid-structure interaction method

Fluid-structure interaction (FSI) studies have become an important tool in the development of wind turbine blades as well as for analyzing and optimizing Horizontal Axis Wind Turbine (HAWT). The most essential elements for estimating the turbine blade strength to withstand extreme wind loads and aerodynamic performance are the blade deformation and the associated stresses. This study aims to compare the strength and analyze the deformation behavior of two models of HAWT blades. A three-dimensional model was created and loaded into a Finite Element (FE) model for analysis. The Computational Fluid Dynamics (CFD) investigation was coupled with the structural model using one-way FSI. In this article, the effect of the aerodynamics on the blade surface of a small HAWT has been studied numerically and experimentally. The airfoil used for the blade profile is S826 airfoil. To provide an appropriate displacement for static measurements, the blade in the experimental investigation is made of thermoplastic polyurethane material (TPU). It is noted that the current experimental findings verify the simulation results, and a comparison between the simulations and the experimental findings reveals a reasonable agreement. The numerical simulations are also implemented on a HAWT epoxy E-glass unidirectional (EEGUD) material. It can be concluded from this study that the blade deformation and stress on the blades are related to the wind speed. The deformation along the span length exhibits nonlinear variation that gradually increases from the blade root and reaches its maximum at the blade tip position. The tip deflection and equivalent stress were found to increase with an increase in wind speed. The dynamic analysis at different tip speed ratios shows the highest deformation at λ = 4, for wind speed of 20 m/s.

Exploring the influence of flexibility on rotor performance in turbulent flow environments

Flexibility plays a crucial role in the design and performance of modern rotors. Its impact on rotor performance and its ability to adapt to external flow disturbances are well-established. In this study, we employ numerical simulations to explore the behavior of a flexible rotor submerged in a turbulent flow, aiming to forecast the influence of its flexibility on performance metrics. The rotational motion of the rotor and the forces imposed by the flow induce deformations in the blades, including bending and twisting. These deformations not only disrupt the flow patterns (vortices) in the turbulent wake but also modify the aerodynamic profiles, thereby affecting essential performance aspects such as thrust, drag, and lift. Our objective is to uncover the relationships between blade deformations, rotation frequencies, and rotor performance in a turbulent flow with a Reynolds number, Re=O(104), and for a tip speed ratio in the range [0,18]. We demonstrate that the mean blade bending angle can be effectively expressed using a modified Cauchy number, revealing a scaling law. We also examined how the aerodynamic performance of the rotor blade is affected by variations in the tip speed ratio, either amplifying or reducing it. Through this research, we advance our understanding of the interplay between rotor flexibility, deformation, and performance, contributing to the optimization of rotor design and operational efficiency.

Tool path modification based on deformation mapping relationship for the adaptive machining of aero-engine blade

The machining efficiency of blade plays an extremely important role in the aero-engine manufacture, especially demanding on the adaptive machining for near-net shape blade. However, the deviation between the actual blade and nominal model can raise serious problems for NC tool path generation. There is a significant demand for directly modifying the nominal tool path based on measurement data in on-site adaptive machining condition. To this end, this paper proposes a tool path direct modification method based on deformation mapping relationship. Decomposing complex blade deformation calculation into the establishment of mapping relationship, including rigid and non-rigid deformation. And parametric modifying each tool axis and center points based on the mapping between tool path contact points and measurement data. The proposed method avoids the tedious model reconstruction process, the topological discontinuity of modified tool path caused by the misaligned error, and the insufficient modification information of tool axis caused by single displacement deformation. A test case of near-net shape blade is given to demonstrate the effectiveness and convenience of the proposed method, and these results shows that the contour error of the adaptive machining area is less than 0.031 mm, and the machining junction of the adaptive machining area and net-shape area could possess a smooth blending.

基于弓背蚁上颚切-锯运动机理的农业仿生刀开发研究

Aiming at issues such as low instantaneous grasping ability, unsatisfactory cutting quality, and proneness to damage of the blades for existing harvesters, by observing the physiological structure and movement characteristics of the ant's mandible and by bionic design theory, a bionic blade was designed to optimize its performance. In this paper, Camponotus was selected as the research object to observe the movement of the right mandibular teeth. It was concluded that the movement of the ant's mandibular teeth was a cutting-sawing motion. A comparative analysis was carried out using the flat blade and the mandibular teeth blade, uncovering that the mandibular teeth movement formed a sliding cut with a variable sliding cutting angle. The mandibular teeth were beneficial for clamping the target and boosting the instantaneous grasping force. The fourth tooth of the mandible was selected as the bionic prototype. from which the contour curve was extracted and analyzed, followed by the design of the bionic blade. Through the finite element method, the influence laws of parameters such as the tooth pitch, structural angle, and blade inclination angle on the stress field and deformation of the bionic blade were analyzed under two force application circumstances: along the inclination direction of the tooth edge and the blade face direction. The results showed that when the applied force was along the tooth edge inclination, the total deformation of the bionic blade initially decreased and then increased with the tooth pitch increase. The maximum equivalent stress of the bionic blade rose gradually with the tooth pitch increase, and the total deformation decreased with the increase of the inclination angle of the tooth. The equivalent stress diminished with the rise in the inclination angle. With the increase of the structural edge angle, the total deformation of the bionic blade rose gradually. When the force was applied along the blade face direction, the deformation and stress values of the blade were significantly lower than those when the force was along the tooth edge inclination. The research findings can offer theoretical references for the design of bionic blades for harvesters.

Study on the Influence of Volute Throat Jet on Excitation Vibration Alleviation of Radial Turbine Blade

Abstract Turbine blade fracture, resulting from high-cycle fatigue (HCF), is the most commonly observed failure mode of turbochargers. In a vaneless turbine, the radial turbine blade is susceptible to HCF under excessive aerodynamic excitation due to the flow field distortion caused by the volute tongue. The present study explores a technique to mitigate blade excitation by reducing pressure disturbance in the volute tongue area. The gas with higher pressure in the inlet section of the volute is transferred to the low-static pressure area upstream of the volute tongue through a throat jet hole. The usage of high-pressure gas improved the homogeneity of the flow field near the volute tongue. The study investigates the mitigation of high-pressure gas jet on turbine blade excitation, the impact of jet hole geometry on the suppression effect of the blade vibration, and the effect of high-pressure jet on turbine performance using numerical simulation of unsteady flow fields. The results indicate that the jet flow has a substantial impact on dampening the blade vibrations. The harmonic pressure amplitude at the monitor point located within the high blade vibration amplitude region is reduced by up to 56%. Generalized pressure analysis reveals that the aerodynamic excitation of the turbine blades is significantly reduced. Experimental evidence verifies the effectiveness of the jet hole scheme in reducing blade vibration. Moreover, the jet hole has a negligible effect on turbine efficiency. However, there is a degree of increased stress in the volute tongue with a jet hole which needs to be evaluated in engineering applications.

Development of nonlinear flat shell element with nonlinear thickness variation for highly flexible wind turbine blade

Large deformation from continuously varied thicknesses on existing and wind turbine blade shell structures is investigated. Various structure models having complicated outer shapes and thickness variations are considered and validated in this paper. A co-rotational method is developed to analyze geometric nonlinearity with a triangular shell structure. The updated stiffness matrix from interpolated thickness function and integral formulation is suggested to consider complicated geometry and thickness variation. Moreover, the co-rotational flat shell element based on the updated stiffness matrix is developed to analyze various nonlinear shell structures, which are the main feature of this research. The numerical analysis for structure deformations show well matched trends in static load analysis. Furthermore, the deformation of a simplified flexible wind turbine blade having tapered geometry and various thickness cases is adopted as a practical case. Moreover, modal analysis for composite beam structure is performed to verify the dynamic problems. The structural behaviors of the nonlinear thickness shell are validated against the solid and the shell models in commercial software, ABAQUS.

Influence of control system on aerodynamic characteristics and elastic deformation of horizontal axis wind turbine blades

Influence of control system on aerodynamic characteristics and elastic deformation of horizontal axis wind turbine blades

Strength and Vibration Analysis of Axial Flow Compressor Blades Based on the CFD-CSD Coupling Method

During the operational process of an axial-flow compressor, the blade structure is simultaneously subjected to both aerodynamic loads and centrifugal loads, posing significant challenges to the safe and reliable operation of the blades. Considering both centrifugal loads and aerodynamic loads comprehensively, a bidirectional CFD-CSD coupling analysis method for blade structure was established. The Navier–Stokes governing equations were utilized to solve the internal flow field of the axial-flow compressor. The conservative interpolation method was utilized to couple and solve the blade’s static equilibrium equation, and the deformation, stress distribution, and prestress modal behavior of compressor blades were mainly analyzed. The research results indicate that the maximum deformation of the blades occurred at the lead edge tip, while stress predominantly concentrated approximately 33% upward from the blade root, exhibiting a radial distribution that gradually decreased. As the rotational speed increased, the maximum deformation of the blades continuously increased. Furthermore, at a constant rotational speed, the maximum deformation of the blade exhibited a trend of first increasing and then decreasing with the increase in mass flow. In contrast, the maximum stress showed a trend of first increasing, then decreasing, and finally increasing again as the rotational speed continuously increased. Centrifugal loads are the primary factor influencing blade stress and natural frequency. During operation, the blades exhibited two resonance points, approximately occurring at 62% and 98% of the design rotational speed.

Comparative study of dynamic characteristics between a FHAWT and a helical type FVAWT

Floating offshore wind turbines (FOWTs) are a growing area of interest, with significant ongoing research work and commercial development. There are two types of FOWT, namely floating horizontal axis wind turbine (FHAWT) and floating vertical axis wind turbine (FVAWT). It has been a long-standing debate on which type of FOWT has better technical and economic performance. However, the research work on comparative study of these two types of FOWT is very rare. In this study, we aim to systematically evaluate the performance of FHAWT and FVAWT, with particular focus on comparing their dynamic characteristics by using coupled numerical models. Tank testing for these two types of FOWT was conducted at the wave basin, and a series of code-to-experiment comparisons were carried out to validate the numerical models. Afterwards, dynamic characteristics, including the control strategy, aerodynamic power, floater motions, tower base bending moments, and blade deformations, are compared between the FHAWT and helical type FVAWT. Results show that the FHAWT presents better performance on the aerodynamic performance and tower base bending moments, while the helical type FVAWT has the advantage of minimal blade deformations.

Vibrational Analysis on Cooling Fan with Induced Mechanical Faults

Abstract This paper reports the investigation of different mechanical faults such as unbalanced loading, broken blades, and deformed blades induced in a fan using vibration analysis. The fan used in this study was a CPU cooling fan as a representation of a basic fan system giving an idea of vibration signatures when it is subjected to faults conditions. This study assists in developing the techniques of condition monitoring for the diagnosis of failures and faults in fan systems while logging the operating status and trend in performance. The investigation is carried out in the turbine testing lab using a Tri-axial accelerometer and a commercial Intel® CPU cooling fan consisting of 7 blades. The fan was run at different RPMs with normal and fault conditions like unbalanced loading conditions induced by adding mass of different weights, breakage of blades, deformation of blades, and holes in the blades. These faults are induced to simulate various mechanical faults that frequently occur in fan-based systems. The vibration data obtained from the accelerometer are filtered and the time series of acceleration values are plotted using MATLAB. For further analysis of data, the Fast Fourier Transform is done to evaluate the peaks of vibration signals in normal and fault conditions. Vibrational amplitude in fault conditions like Hole-2 has 4.5 times higher amplitude than normal and Cut-2 has 31.5 times higher amplitude.

Research on the Blades and Performance of Semi-Submersible Wind Turbines with Different Capacities

With the gradual increase in the maturity of wind energy technology, floating offshore wind turbines have progressively moved from small-capacity demonstrations to large-capacity commercial applications. As a direct component of wind turbines used to capture wind energy, an increase in the blade length directly leads to an increase in blade flexibility and a decrease in aerodynamic performance. Furthermore, if the floater has an additional six degrees of freedom, the movement and load of the blade under the combined action of wind and waves are more complicated. In this work, two types of semi-submersible wind turbines with different capacities are used as the research objects, and the load and motion characteristics of the blades of these floating offshore wind turbines are studied. Through the analysis of the simulation data, the following conclusions are drawn: with the increase in the capacity of the wind turbine, the flexible deformation of the blade increases, the movement range of the blade tip becomes larger, the blade root load increases, and the power fluctuation is more obvious. Compared with the bottom-fixed wind turbine, the flexible blade deformation of the floating offshore wind turbine is smaller; however, the blade root load is more dispersed, and the power output is more unstable and lower.

A prediction method for blade deformations of large-scale FVAWTs using dynamics theory and machine learning techniques

There is renewed interest in floating vertical axis wind turbines (FVAWTs) as offshore wind turbines progressively increase in size and move into deeper waters. To explore the potential of large-scale FVAWTs for future commercialization, it is crucial to investigate blade deformations using an accurate and effective method. In this study, we developed a hybrid model, namely, the SVST-ANN, which integrates dynamic theory and machine learning techniques to predict blade deformations. Specifically, an artificial neural network (ANN) module is incorporated into the slack coupled vertical axis wind turbine simulation tool (SVST), which significantly reduces the total computational time. A comparative study was conducted between the SVST-ANN model and the traditional SVST model, employing a 10 MW helical-type FVAWT as an example. The results show that the SVST-ANN model can accurately and efficiently predict blade deformations. The maximum errors for the maximum value, average value, and standard deviation across all nodes are minimal, with a corresponding computational time reduction of approximately 60 %. This study provides a novel method for investigating the dynamic behavior of the FVAWTs, which is more effective for calculating the elastic deformations of blades than traditional numerical methods.