Small Wind Turbine Blade Research Articles

Development of High Performance Airfoils for Application in Small Wind Turbine Power Generation

Small wind turbine power generation systems have the potential to meet the electricity demand of the residential sector in developing countries. However, due to their exposure to low Reynolds number (Re) flow conditions and associated problems, specific airfoils are required for the design of their blades. In this research, XFOIL was used to develop and test three high performance airfoils (EYO7-8, EYO8-8, and EYO9-8) for small wind turbine application. The airfoils were subsequently used in conjunction with Blade Element Momentum Theory to develop and test 3-bladed 6 m diameter wind turbine rotors. The aerodynamic performance parameters of the airfoils tested were lift, drag, lift-to-drag ratio, and stall angle. At Re=300,000, EYO7-8, EYO8-8, and EYO9-8 had maximum lift-to-drag ratios of 134, 131, and 127, respectively, and maximum lift coefficients of 1.77, 1.81, and 1.81, respectively. The stall angles were 12° for EYO7-8, 14° for EYO8-8, and 15° for EYO9-8. Together, the new airfoils compared favourably with other existing low Re airfoils and are suitable for the design of small wind turbine blades. Analysis of the results showed that the performance improvement of the EYO-Series airfoils is as a result of the design optimization that employed an optimal thickness-to-camber ratio (t/c) in the range of 0.85–1.50. Preliminary wind turbine rotor analysis also showed that the EYO7-8, EYO8-8, and EYO9-8 rotors had maximum power coefficients of 0.371, 0.366, and 0.358, respectively.

Feasibility of Bladder Compression Molded Prepreg as Small Wind Turbine Blade Material

풍력터빈 블레이드는 바람의 운동에너지를 축일로 변환하는 장치로서 상대적으로 고속 회전하면서 양력과 항력의 다양한 하중 조합과 진동에 견딜 수 있도록 내구 강도가 큰 경량의 재료를 선택하여 강성을 증가시키는 구조를 갖도록 설계되어야 한다. 본 연구는 CFRP 프리프레그를 사용하여 소형 풍력 블레이드를 제작하는 경우 공정 시간을 단축하는 기술을 개발하려는 목적으로 수행되었다. QBlade 수치해석 프로그램을 사용하여 블레이드의 형상을 결정하였다. 주어진 풍속에서 바람에 의해 부가되는 양력과 항력을 계산하는 유체역학 수치해석을 수행하고, 대표적인 블레이드 구조에 대해 블레이드 외피 재료에 가해지는 폰미세스 응력을 예측하는 재료역학 수치해석을 수행하였다. 인장 강도 시험의 불확실도를 개선하기 위해 ASTM D638 규정을 수정하여 새로운 시편의 형상을 제안하였고, 기존 형상의 인장 강도와 유사한 평균값을 얻되 파단 위치의 재현성이 향상됨을 확인하였다. 일련의 실험을 통해 소형 풍력 블레이드의 제작에 블래더 가압 방식을 적용하면 충분한 내구 강도를 확보하면서 공정시간을 단축할 수 있음을 확인하였다.

Experimental Study on Modal and Harmonic Analysis of Small Wind Turbine Blades Using NACA 63-415 Aerofoil Cross-Section

This work focused on modal and harmonic analysis of small wind turbine blades taken from the NACA 63415 series. The sandwich structure type composite blade is fabricated from GFRP and epoxy with Uni-vinyl hard foams of different alignments as stiffeners. In this work, the modal and harmonic analysis of different varieties of blades like solid, hallow and rectangular alignment blades is carried out by the finite element method using ANSYS 18.1 software. From Finite Element Analysis, the natural frequencies, amplitudes and mode shapes are obtained. Based on the working principle of wind turbine blades, the boundary conditions are applied. The experimental investigation is also done using a vibration test rig with specially designed fixtures. The forced vibration approach is used to analyze the responses of the blade with different forces and frequencies which gives the feasible study to define the effective blade structure. In addition to modal analysis, the harmonic analysis is also carried out for different materials to find the amplitude at different frequencies. The outcome of this analysis can be used as a reference for improving the structure and material properties of the blade.

Evaluation of Small Wind Turbine Blades with Uni-Vinyl Foam Alignments Using Static Structural Analysis

Mechanical characteristics of small wind turbine blades of National Advisory Committee for Aeronautics (NACA) 63-415 series with different Univinyl (UV) foam alignments have been evaluated experimentally using Universal Tes... | Find, read and cite all the research you need on Tech Science Press

Design and Analysis of Dimple Arrangement on a Small Wind Turbine Blade

This article predominantly focuses on the performance estimation of a small wind turbine blade when a dimple arrangement is made along its upper surface. The dimple arrangement is grooved at two locations: 0.25c and 0.5c, where c is the chord length of the turbine blade. A CFD analysis using the k-ε turbulence model is carried out on the selected blade sections NREL S823 and S822. The continuity and momentum equations are solved using ANSYS Fluent Solver to assess the aerodynamic performance of the proposed design. The effect of introducing a dimple on the blade surface has shown to delay the flow separation, with the formation of vortices. Further, the overall performance of the blade is simulated using GH BLADED and the results acquired are discussed.

Small Wind Turbine Blade Design and Optimization

This work aims at designing and optimizing the performance of a small Horizontal-Axis-Wind-Turbine to obtain a power coefficient (CP) higher than 40% at a low wind speed of 5 m/s. Two symmetric in shape airfoils were used to get the final optimized airfoil. The main objective is to optimize the blade parameters that influence the design of the blade since the small turbines are prone to show low performance due to the low Reynolds number as a result of the small size of the rotor and the low wind speed. Therefore, the optimization process will select different airfoils and extract their performance at the design conditions to find the best sections which form the optimal design of the blade. The sections of the blade in the final version mainly consist of two different sections belong to S1210 and S1223 airfoils. The optimization process goes further by investigating the performance of the final design, and it employs the blade element momentum theory to enhance the design. Finally, the rotor-design was obtained, which consists of three blades with a diameter of 4 m, a hub of 20 cm radius, a tip-speed ratio of 6.5 and can obtain about 650 W with a Power coefficient of 0.445 at a wind-speed of 5.5 m/s, reaching a power of 1.18 kW and a power coefficient of 0.40 at a wind-speed of 7 m/s.

Comparative Fatigue Life Assessment of Wind Turbine Blades Operating with Different Regulation Schemes

A comparative evaluation of the fatigue damage occurring in the blades of small wind turbines, with different power regulation schemes, has been conducted for the first time. Three representative test cases were built, one based on stall regulation and two using pitch regulation. The power curves were tuned to be identical in all cases, in order to allow for a direct comparison of fatigue damage. A methodology combining a dynamic simulation of a wind turbine forced by stochastic wind speed time series, with the application of the IEC 61400-2 standard, was designed and applied for two levels of turbulence intensity. The effect of the wind regime was studied by considering Weibull-distributed wind speeds with a variety of parameter sets. Not unexpectedly, in typical wind regimes, stall regulation led to a generally higher fatigue damage than pitch regulation, for similar structural blade design, but the practical implications were smaller than thought previously. Given the need for cost-effective designs for small wind turbines, stall regulation may be a viable alternative for off-grid applications.

Structural health monitoring of critical zones of small wind turbine blades for domestic users

The most important part of wind turbine is the blade that must be tested during fabrication and functioning when can be damaged by moisture absorption, fatigue, wind guests or lightning strikes. The fibers can also appear and develop under moderated loads or cracks and delaminating due to the low energy impacts etc. The aim of this paper is to identify the modal behavior of small wind turbine blade in terms of the signal convergence, modal evolutions and frequency spectra. There are numerous methods for monitoring and detecting structural damage of the wind blades, but in this study it was used the impact hammer method. The results emphasized the natural frequencies, the modal shape of structure and the signal coherence captured in different points.

Effect and detection of cracks on small wind turbine blade vibration using special Kriging analysis of spectral shifts

Undetected micro-cracks in wind turbine blades lead to failure and costly repairs. Effective remedies depend on proactive measures taken to detect such cracks at early stages. Defects and cracks cause certain shifts in resonant peaks amplitude and frequency (spectral shifts) of the blade depending on the location and dimensions of the crack or damage. Precise location of the crack is difficult to ascertain due to its small dimensions and random causes. This study developed a special Kriging model for predicting crack location using spectral shifts in the blade’s resonant peaks. Records of blade’s spectral shifts collected for known crack locations were used to construct the Kriging model. The model predicts crack location by correlating spectral shifts of cracked blade with spectral shifts recorded from blades with known crack locations. Experimental validation demonstrated the ability of the method to detect micro crack locations with an accuracy of 95%. Experimental results are presented and discussed.

Measurement of quality test of aerodynamic profiles in wind turbine blades using laser triangulation technique

AbstractThe development of an optical contact instrument for measuring the geometric shape of aerodynamic profiles on blades of small power wind turbines is presented. The instrument uses the triangulation principle, where a structured line laser pattern is projected onto the surface of one of the faces of the blade under test, a camera captures the image of the line and is processed to interpret the distorted form of the projected line. A linear sweep of the instrument makes it possible to measure the profile in another section of the blade. Comparison and evaluation results of two symmetric profiles of the NACA 0012 family are presented, one manufactured in a 3D printer and the other one is a metal profile AF104 of a subsonic wind tunnel. Additionally, three sections of a blade with profile FX 63‐137 of a 1.5 kW wind turbine were evaluated. An aerodynamic analysis shows a reduction in the lift coefficient and in the efficiency of the aerodynamic profile, as well as an increase in the drag coefficient. The sensitivity of the instrument is 0.1 mm on the Z‐axis.

Investigation of stiffness of small wind turbine blade based on vibration analysis technique

In this article, three small wind turbine blades of different materials were manufactured. Finite element analysis was carried out using finite element software ANSYS 14.5 on modeled blades of National Advisory Committee for Aeronautics 4412 airfoil profile. From finite element analysis, first, two flap-wise natural frequencies and mode shapes of three different blades are obtained. Experimental vibration analysis of manufactured blades was carried out using fast Fourier transform analyzer to find the first two flap-wise natural frequencies. Finally, the results obtained from the finite element analysis and experimental test of three blades are compared. Based on vibration analysis, we found that the natural frequency of glass fiber reinforced plastic blade reinforced with aluminum sheet metal (small) strips increases compared with the remaining blades. An increase in the natural frequency indicates an increase in the stiffness of blade.

Investigation of Blade Geometry and Airfoil for Small Wind Turbine Blade

Investigation of Blade Geometry and Airfoil for Small Wind Turbine Blade

Effects of Leading Edge Erosion on the Power Performance and Acoustic Noise Emissions of Locally Manufactured Small Wind Turbine Blades

The local manufacturing of small wind turbines has become increasingly popular over the last decade, among international networks of renewable energy practitioners, for the implementation of rural electrification applications. Locally manufactured small wind turbines (LMSWTs), used most frequently in off-grid battery based renewable energy systems, typically utilize wooden blades and coreless axial flux permanent magnet generators due to their simple manufacturing process and local availability of materials. In this paper the effects of leading edge erosion on locally manufactured small wind turbine blades are researched experimentally, both in terms of power performance and acoustic noise emissions. From the research it is concluded that a yearly maintenance of the wooden blades of a LMSWT can lead to less acoustic noise emissions and better power performance, with the latter becoming more significant as the mean wind speed of the installation site increases. For practitioners, installers and manufacturers of LMSWTs, these findings can significantly guide manufacturing processes and techniques in terms of preventing leading edge erosion, while also advising preventative maintenance procedures on the field, in order to keep small wind electric systems quiet and productive.

Evaluation of Basalt Fibers on Wind Turbine Blades through Finite Element Analysis

Here we use finite element analysis to determine the suitability of basalt fiber as a substitute for E-glass in structural applications, which would improve the cost effectiveness of small wind turbine blades. Five NACA (National Advisory Committee for Aeronautics) profiles were evaluated to select the optimum shape for the wind operation conditions. To obtain the wind load pressure distribution over the blade, a computational aerodynamic analysis by CFD (computational fluid dynamics) was performed based on the blade’s design and operating conditions. Material properties and mechanical tests were carried out to obtain the fiber volume fraction, density, Young’s modulus, shear modulus, and Poisson relation of polymeric matrix composites made using basalt and fiberglass. The obtained wind loads and material properties were used on a FEM (finite element model) analysis to evaluate the structural behavior of the blade under normal and critical operating conditions. Both fibers meet the structural requirements under normal operating conditions. We detected a reduction of 4% in the blade stress when basalt fibers are used instead of glass fibers, and a reduction of 68% in the total deformation for a critical load case of 40 m/s was obtained when using basalt fibers, which met the structural requirements and maximum power generation required for this wind turbine design.

Optimized design and performance parameters for wind turbine blades of a solar updraft tower (SUT) plant using theories of Schmitz and aerodynamics forces

For extracting maximum power output from the wind, it is very important that the blades of a small wind turbine should rotate at any range of wind velocity. A step has been taken to estimate the optimized design and performance parameters of small scale wind turbine blades for a solar updraft tower (SUT). The pitch angle (β), relative wind angle (φ), lift force (dFL) and relative chord length (c/R) of rotor blade are estimated and optimized using conservation of angular momentum (Schmitz theory) and theory of aerodynamic forces on an airfoil. For different blade segments, dFL and power generation were evaluated and analysed. β, φ and dFL were optimised such as 18.4°, 26.4° and 0.0052 N, respectively, for achieving the maximum power output of 0.06 W at lower wind velocities (2 m/s). At higher wind velocities (10 m/s), the above parameters are optimised as 42.9°, 50.94° and 0.168 N, respectively for achieving a maximum power output of 1.75 W. The optimized values are compared with values from literature and these were found to be in reasonable agreement.

Damage detection in a laboratory wind turbine blade using techniques of ultrasonic NDT and SHM

AbstractThis paper presents a case study in the use of ultrasonic NDE/SHM techniques for detecting and locating damage in a real (but small) wind turbine blade. Two techniques are considered: (1) non‐linear acoustics, and (2) guided‐wave “pitch‐catch” SHM. While the non‐linear acoustics approach proved disappointingly insensitive to damage induced experimentally in the blade, the guided‐wave approach not only detected the damage but also proved capable of locating it, using a “network of novelty detectors” methodology. A first, slightly ill‐conceived, programme of guided‐wave tests actually provided valuable insight into attenuation of waves in the structure of interest and supported the idea that actuator‐sensor networks of a feasible density could be used for wind turbine blade SHM.

Review on Aerodynamic Shape Optimization through Parametric Study using Computational Fluid Dynamics Analysis on the Small Wind Turbine Blade

Review on Aerodynamic Shape Optimization through Parametric Study using Computational Fluid Dynamics Analysis on the Small Wind Turbine Blade

Optimum design of a small wind turbine blade for maximum power production

The rotor blades of a wind turbine are critical components that consist of aerodynamic shapes called airfoils. The interaction of these airfoils with the wind allows converting the power in the wind to mechanical power. The structure of the rotor blades must be able to extract maximum energy from the wind while being strong enough to stand steady, periodic and randomly changing loads. For maximum power extraction, an optimum design of the rotor blades is necessary. This paper presents a typical design methodology of the rotor blades of a small wind turbine with a power generation of 11 kW (rotor radius of 3.5 m). First, the design parameters were presented. Then, optimum blade geometry (chord length and twist angle distribution) was determined using optimum rotor theory. Finally, the wind turbine blade performance (power coefficient and power production) was assessed using Q-blade software.

Assessing the IEC simplified fatigue load equations for small wind turbine blades: How simple is too simple?

Abstract It is well known that wind turbine blades are fatigue critical, with much literature and methodologies available for assessing fatigue loading of large wind turbine blades. Little research effort has been directed at assessing the fatigue life of small wind turbines which operate at higher rotational speeds and are subject to highly unsteady aerodynamic loading. In this paper the simplified load model proposed in IEC 61400.2 is used to determine the fatigue life of a small 5 kW wind turbine blade. This estimated life is compared to that determined from both measured operational data and aeroelastic simulations. Fatigue life was estimated by the standard at 0.09 years, compared to 9.18 years from field measurements and 3.26 years found via aeroelastic simulations. All methods fell below the 20 year design life, with the standard over-conservative by a factor of 102 and 36 for measurements and simulations respectively. To the best of the authors' knowledge these three fatigue methods specified in the standard have not been quantitatively compared and assessed for small wind turbines. Results are of importance to small wind turbine developers as they seek best practice for determining blade fatigue life. Shortcomings of the IEC methodology are detailed and discussed.

Vibration control of small horizontal axis wind turbine blade with shape memory alloy

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.