Horizontal Axis Wind Turbine Blade Research Articles

Experimental Validation of a Passive-Adaptive Slat Concept and Characterization under Sinusoidal Fluctuations in the Angle of Attack

This article presents an experimental investigation of a passive-adaptive slat concept, an aerodynamic control mechanism aimed at avoiding separation in the inwards region of a horizontal axis wind turbine blade. The passive-adaptive slat is designed to autonomously adjust its position due to the aerodynamic forces acting on it, without the need of any active control system or external power source. The slat opens when the angle of attack increases beyond a certain threshold so that stall is delayed and closes for smaller angles of attack to increase the lift-to-drag ratio of the airfoil. A thorough aerodynamic characterisation of the passive-adaptive slat is performed in the wind tunnel followed by testing it under different sinusoidal inflows generated by a 2D active grid. It is observed that the slat system is able to leverage the advantages of both a clean airfoil and an airfoil with a fixed slat. It has the capability of delaying stalls for higher angles of attack, as well as having higher lift-to-drag ratio for lower angles of attack. It is also observed that, for fluctuating inflow, the passive-adaptive slat is able to achieve similar mean lift values as an airfoil with fixed slat while showing significant reduction in the lift fluctuations.

Development and Testing of a High Performance Airfoil for Application in Small Horizontal Axis Wind Turbine Blades

Development and Testing of a High Performance Airfoil for Application in Small Horizontal Axis Wind Turbine Blades

A frost ice formation method of horizontal axis wind turbine blade based on polynomial fitting

In this paper, a new direct calculation method of frost ice shape on the blade surface of horizontal axis wind turbine is proposed. Using linear interpolation algorithm, the airfoil ice shape obtained by LEWICE 2D software or ice wind tunnel experiment was fitted with equidistant step length in the first and fourth quadrants and equidistant step length in the second and third quadrants. The key point coordinates of ice shapes on cross-sections along the span-wise were mapped into lagging and flapping surfaces through the mathematical dimension reduction, respectively. The polynomial fitting was used to deal with ice projection points of multiple sections in lagging and flapping surfaces, and then the blade’s frost ice shape was obtained. By calculating the sum of squared residuals of the polar diameter at the same polar angle, the errors between experimental and airfoil frost shape fitting methods, experimental and FENSAP, and blade frost shape formation methods and FENSAP were analyzed. The results show that the new method is in good agreement with the ice shape of FENSAP simulation results and experimental results. The residual sum of squares is small. This method makes the analysis of frost ice morphology of wind turbine blades do not need to consider interdisciplinary. The calculation process is simple and reliable.

A study on coupled edgewise and flapwise vibration modes of wind turbine blade

The coupled flapwise and edgewise vibrations of a horizontal axis wind turbine blade (HAWT) are discussed in this paper. Kinetic and potential energies of the blade are evaluated with consideration of the effects of gravity and aerodynamic forces. Hamilton’s principle is employed to develop the nonlinear coupled modal equations of the blade. The coupling between the first order edgewise and the first two order of flapwise modes is considered. This leads to three equations with nonlinear terms. Multiple-scales perturbation method is employed to solve these equations. Furthermore, the numerical values of structural specifications of National Renewable Energy Laboratory (NREL) 5-MW reference wind turbine blade are used, for example. It is shown that first edgewise and first flapwise vibrations are dominant, while second flapwise mode of vibration is less significant in the case of transient responses. Energy transfer between resonant modes is observed in both internal and combination resonances. The amplitude–frequency curves and phase diagrams during primary and combination resonances are obtained for the steady-state responses. Combination and primary resonances are further examined by considering various factors such as geometric nonlinearity and aerodynamic force.

Design optimization of three‐dimensional geometry of a micro horizontal axis wind turbine blade using the response surface method

AbstractThis study presents an aerodynamic design optimization of a micro micro‐horizontal‐axis wind turbine (HAWT). To obtain an optimal design, it is essential to understand the design parameters and select the responsible factors that affect the blade efficiency. The aim of this work is to redesign a 3D micro‐HAWT to improve aerodynamic performance, through improving the distribution of chord length and twist angle along the blade. Performance analysis and flow visualization of the initial design and the optimal design were carried out using CFD analyzer. In the blade optimization design, eight significant input parameters were selected, five to characterize the chord length distribution and three to represent the twist angle along the blade. To maximize the efficiency, design points that are created by Design of Experiment (DoE) are evaluated through (Multi‐Objective‐Genetic Algorithm) MOGA method. The results showed a reduction on the separation effect area on the optimal blade surface compared to the initial one. The use of response surface optimization (RSO), when combined with CFD simulation, has proven beneficial in selecting the optimal HAWT design. Finally, the open source software (Qblade) was used to investigate and to compare the performance of the initial and optimum design. An efficiency enhancement of approximately 3.6% is achieved at tip speed ration TSR = 3.4.

Optimal airfoil selection for small horizontal axis wind turbine blades: A multi-criteria approach

Over the last century, the growing demand for clean energy has emphasized wind energy as a promising solu-tion to address contemporary energy challenges. Within the realm of wind energy, the wind turbine plays a pivotal role in harnessing the kinetic energy of the wind and converting it into electrical power. Among the various components of the wind turbine system, turbine blades assume a critical role in capturing the wind's kinetic energy and converting it into rotational motion. Consequently, the design of wind turbine blades holds the utmost importance in determining the overall performance and efficiency of the entire wind turbine system. One essential aspect of blade design involves selecting an appropriate airfoil. Throughout history, numerous airfoil profiles have been developed for various applications. Notably, National Advisory Committee for Aeronautics (NACA) and National Renewable Energy Laboratory (NREL) airfoils have been tailored for aircraft and large-scale wind turbine blades, respectively. However, the quest for suitable airfoil types for small-scale wind turbine blades has been ongoing. This study delves into an examination of over 62 distinct NACA and NREL aerofoil types tailored for small horizontal-axis wind turbine blades. Employing specialized software, namely QBlade, specifically designed for modeling and simulating wind turbine blades, the study calculates key parameters such as power output, stress, deformation, and weight for each airfoil. Subsequently, based on the simulated data, the optimal airfoil is identified using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) multi-criteria selection approach. This selection process takes into account simulation results pertaining to power output, stress, deformation, and weight. The decision-making process involving multiple criteria is facilitated using Excel and Python. The findings of this study reveal that among the 62 airfoil types under consideration, the NACA 0024, NACA 2424, and NACA 4424 airfoils emerge as the most suitable choices for small horizontal-axis wind turbine blades.

Improved Design For Horizontal Axis Wind Turbine Blades With Winglets

The horizontal axis wind turbine blades are modified to enhance the turbine's aerodynamic performance. The performance of the modified geometry was evaluated by comparing the lift, drag and torque findings to the same propeller with a straight leading edge. The symmetrical airfoil of NACA 0012 was chosen for the turbine blade profiles. The computational fluid dynamics (CFD) simulation was performed using the shear stress transport (SST) k-ω turbulence model to capture the vortical structures for the inlet wind speed of 20 m/s. From the simulation results, it has been shown that the four blades with winglets at 15° angle of attack (AoA) orientation turbine have demonstrated the highest aerodynamic performance. It produces the lowest aerodynamic drag and the most increased torque for turbine rotations, which, in return, carries many economic advantages such as energy savings, low impact on the environment, reduced maintenance requirements, and less noise.Keywords: Aerodynamics, CFD, drag, horizontal axis wind turbine, lift, winglets

Performance estimation of small‐scale horizontal axis wind turbine blade

AbstractThe extracted energy from the wind is mainly influenced by the geometry of the rotor blades. Determining the aerodynamic optimum blade shape is one of the main tasks of the wind turbine designer. In the current study, the mixed airfoil technique was employed by using “Blade‐Element‐Momentum” (BEM) and “Computational‐Fluid‐Dynamics” (CFD) analysis to predict the aerodynamic performance of a small‐scale horizontal axis wind turbine blade. The BEM was then run using the open‐source wind turbine design and performance computation program Q‐Blade. The numerical simulation is carried out by Ansys Fluent. Here, the k‐ω Shear Stress Transport (SST) model was used. The results were compared with existing experimental data on lift and drag coefficients at the optimal angle of attack. The results of the two approaches were compared for different tip speed ratio values and a good agreement between CFD and BEM results was found.

Designing, Solid Modeling and Stress Analysis of Horizontal Axis Wind Turbine Blade

Wind energy is one of the clean renewable forms of energy that can handle the existing global fossil fuel crisis. Wind energy is captured by Wind turbine which converts kinetic energy of the wind into the mechanical energy and then this energy is transformed into electrical energy. The objective of this study is to design a 5kW wind turbine blade which includes selection of the blade airfoil based on CL/CD ratio, linearization of geometric parameters of the blade, solid modeling of blade profile and estimation of tangential, thrust forces and total power of the designed blade with the selection of the best material.

Stress Characteristics of Horizontal-Axis Wind Turbine Blades under Dynamic Yaw

The dynamic yaw significantly affects the aerodynamic load distribution of wind turbines, and the aerodynamic load is one of the main influencing factors of wind turbine structural stress variation. Taking the NACA4415 horizontal axis wind turbine designed by the research group as the research object, the numerical simulation was used to analyze the distribution characteristics of blade stress, surface thrust coefficient, and the wind turbine power output under periodic dynamic yaw conditions. The results show that the blade stress, blade axial thrust, and wind turbine output power were presented as a cosine distribution with yaw fluctuations. The distribution trend of blade stress showed an increase followed by a decrease from the inside out along the span direction. In addition, due to the influence of dynamic yaw and aerodynamic loads, the stress values near the blade root exhibited significant fluctuations. With the increase in tip speed ratio, the stress values of dynamic windward yaw gradually exceeded those of leeward yaw. Within the range of a 10° to 30° yaw variation period, the stress value with positive yaw was larger than that with negative yaw, and the highest stress value occurred in the range of −5° to 15°. The results can be provided as a theoretical basis for the structural design and yaw control strategies of wind turbines, considering dynamic yaw operation.

Simultaneous aerodynamic and structural optimisation of a low-speed horizontal-axis wind turbine blade using metaheuristic algorithms

AbstractThis work presents a concurrent design and multi-objective optimisation framework of horizontal axis wind turbine blades, made of composite material, for low wind speed. The optimisation model aims to minimise the structural mass of the blade whilst simultaneously maximising the turbine power output, subjected to three constraints viz. blade tip deflection, and Tsai-Hill and von Mises criteria. The design variables are blade shape and details of the internal blade structure. The control points and polynomial interpolation technique were adopted to determine the blade shape while the airfoil types at blade sections remained fixed. The internal blade structure design variables include the thickness of ribs and spars and the carbon fibre thickness and orientations. The blade element momentum approach is utilised to calculate turbine power and structural loads, whereas a finite element method is employed for structural analysis. Twelve multi-objective metaheuristics algorithms are used to solve the proposed multi-objective optimisation problem while their performance is investigated. The results obtained show that the multi-objective cuckoo search algorithm is the most efficient method. This study is said to be the baseline for a future study on multi-objective optimisation which combines two design stages of the composite low-speed wind turbine blades.

Horizontal axis wind turbine blade (HAWT) analysis based on blade element momentum theory (BEM) for some cities in Nigeria

In this research, the blade element momentum (BEM) theory of a horizontal axis wind turbine (HAWT) blade with 1 kW power output has been analysed for one station across the six geopolitical zones. Twenty years wind speed data (2000 – 2020) obtained from Nigeria meteorological Agency (NIMET) Head quarter, Abuja. In an effort to optimally explore and utilize wind energy, an optimal design of wind turbine blade needs to be obtained. Therefore, a computational method to analysed and optimize the performance of the wind turbine blades needs to be developed. For that purpose, a computational method based on the Blade Element Momentum (BEM) theory is developed in this study. In this method, the blade of a wind turbine is divided into several elements and it is assumed that there is no aerodynamic interaction amongst the elements. Furthermore, this (BEM) method incorporated with equations from momentum and blade element theories to obtain equations which are useful in wind turbine blades design process. In this research a computed result for aerodynamic characteristics based on BEM theory shows that, Maiduguri Metropolis is suitable for surface wind electrification among the selected stations with an estimated maximum wind power of 1.774𝑘𝑊 at total lift to drag ratio (𝐹𝐿/𝐹𝐷) of 27.2674 and a mean relative velocity of 14.99m/s. There is an agreement with my findings and that of other researchers.

Optimization and Experimental Investigation of 3D Printed Micro Wind Turbine Blade Made of PLA Material

This paper presents the design, development, and optimization of a 3D printed micro horizontal axis wind turbine blade made of PLA material. The objective of the study was to produce 100 watts of power for low-wind-speed applications. The design process involved the selection of SD7080 airfoil and the determination of the material properties of PLA and ABS. A structural analysis of the blade was carried out using ANSYS software under different wind speeds, and Taguchi's L16 orthogonal array was used for the experiments. The deformation and equivalent stress of the PLA material were identified, and the infill percentage and wind speed velocity were optimized using the moth-flame optimization (MFO) algorithm. The results demonstrate that PLA material has better structural characteristics compared to ABS material. The optimized parameters were used to fabricate the turbine blades using the fusion deposition modeling (FDM) technique, and they were tested in a wind tunnel.

The Influence of Gravitational Stiffening and De-stiffening on Nonlinear Dynamic Behavior of Vertical Beams with Cracks

ABSTRACT Dynamics of vertically oriented blades is an important topic of research as it replicates the physical behaviour of several real-time applications such as horizontal axis wind turbine blades. It is observed that available literatures explaining the effects of gravity on the dynamic behaviour of vertical beams/blades did not focus on the various operational adversities such as geometric nonlinearities, possibilities of crack initiation due to adverse conditions. Therefore, in present study, an attempt is made to capture reverberations of gravity on cracked vertical blades including geometric nonlinearity. A computationally efficient numerical model for nonlinear dynamic analysis of vertically oriented cracked blades is developed. Efficacy of proposed model is verified by several case studies. Subsequently, parametric investigation is performed for combined effects of crack and gravity on the dynamic response. Crack and gravity dominant regions based on slenderness ratio are identified for the first time . Furthermore, influence of nonlinearities on such behaviour provides useful insights to anticipate the mechanics of the dynamic behaviour of a vertical cracked cantilever beam. Proposed work may be useful for developing a robust vibration-based condition monitoring for a given application which involves hanging beams with a possibility of crack such as rotor blades.

Aerodynamic Performance Investigation of a Small Horizontal Axis Wind Turbine with Multi-Airfoil Blade Profiles of SD2030 and E231 Using Wind Tunnel Experiments and BEM Theory Method

The goal of this study is to investigate the performance of a small horizontal axis wind turbine blade at wind speeds of lower than 5 m/sec numerically and experimentally. The rotor blade has a diameter of 0.7m and consists of two airfoils profile: the thin airfoil SD2030 selected at the outboard region, and the thick airfoil E231 at the inboard region. The former airfoil, SD2030, is highly recognized for aerodynamic performance as it is suitable for low Reynolds number (Re), while the latter airfoil E231 is likewise appropriate for low Re flow but has a higher thickness-to-chord ratio which acts as structural support and good strength at the hub. The selected airfoils were analyzed using QBlade software based on XFOIL and Blade Element Theory (BEM) for different Reynolds number. Using a low-speed wind tunnel and Reynolds number ranging from 1x105 to 5x105, experiments at pitch angles of 5ο were conducted to determine the variation in torque and predict blade performance. The results reveal that the turbine with two hybrid different airfoil profiles have achieved a better start-up response at low wind speed of 1.5 m/s and a high-power coefficient of 0.34 with 3.7 tip speed ratio. The turbine can be used to generate a power of 0.5W at 1.5 m/s and a maximum power harvest of up to 20W at a wind speed of 7m/sec. The turbine's performance compared to other small wind turbines from the literatures demonstrate good performance and the results obtained from wind tunnel data were found in satisfactory agreement with the results provided by the BEM code.

Design of a small-scale wind tunnel for the study of horizontal-axis wind turbine blades

The paper considers the details of design and construction of a small-sized wind tunnel with an open circuit and a closed test section for investigating the blades of horizontal-axis wind turbines. The effect of different types of jet straighteners on the turbulence of the flow in the test section has been studied. Turbulence flow distributions Tu at Reynolds numbers Re from 5·103 to 2·104 are obtained using Laser Doppler Anemometry methods. As a result, the wind tunnel design with average flow turbulence of 1.6 % is obtained. The flow visualization of NACA 64-618 airfoil at Re = 5·103 is obtained.

Examining adequacy of the empirical Theodorsen function for wind turbine blade section-model aeroelasticity

The ability to reproduce aeroelastic loads of horizontal-axis wind turbine blade cross sections by Theodorsen function, currently employed by researchers and practitioners, is investigated. Section model experiments are conducted on two reduced-scale models of airfoil sections, derived from a benchmark large-scale wind turbine blade. Uncertainties associated with aeroelastic properties of the wind turbine blade sections, measured in the wind tunnel, are also examined. Uncertainties are associated with random, experimental laboratory errors. Statistical inference is utilized to characterize experimental errors. The results suggest that the Theodorsen function cannot be used while empirical aeroelastic coefficients (Scanlan derivatives), dependent on the cross-section geometry, are necessary. Furthermore, experimental errors, aptly quantified in this study, should be incorporated and included in reliability analyses of wind turbine blades.

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.

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.

Strength analysis of a blade with different cross-sections

The efficiency of horizontal axis wind turbine (HAWT) blades is examined in this paper concerning the effect of cross-section airfoil type. Three different airfoils were examined: symmetric (NACA 4412), asymmetric (NACA 0012), and supercritical (NACA 4412). (EPPLER 417). The analyses that were performed combined theory and experiment. Theoretical analyses were carried out using Fortran 90 code and the blade element momentum-based Qblade code. The blade was created using SolidWorks software and a 3D printer for testing purposes. The findings of experimental tests supported the conclusions of the theory. Research revealed that the EPPLER 417 blade, which has a supercritical airfoil, performed better than other examined objects. NACA 4412, NACA 0012, and EPPLER 417 each have a power coefficient of 0.516, 0.492, and 0.510. According to the experimental data, the EPPLER 417 airfoil outperforms other air-foils in terms of power and speed reduction. To calculate the deformation and stresses of the three blades with various cross sections, CFD analysis was done in ANSYS Workbench. The CFD results showed that NACA 4412 has the highest strength but EPPLER 417 was considered the optimum cross-section based on power generation and acceptable stress values.