Improved toggle-brace viscous damper for vibration mitigation of wind turbine blade

Renewable energy has increased in recent years with a consequential increase in equipment maintenance. Maintenance costs can be reduced by structural health monitoring techniques especially for wind turbine (WT) blade damages. However, the majority are not suitable for on-line measurements and quantitative detections. A quantitative damage detection method is developed to identify multiple damages in a WT blade under in-service operation conditions. Firstly, singular value decomposition is applied to reveal singular information in the operating deflection shape (ODS), which can be treated as damage locations. Secondly, whale optimization algorithm is utilized for a damage severity decision about the natural frequency database between damage severities and natural frequencies, which are constructed by finite element method (FEM) simulations on the detected damage locations in the WT blade. The procedure is applied to FEM numerical simulations of a single WT blade with two and three damages. By adding a certain noise to the simulation dataset, the robustness of the present method is validated. Furthermore, the laser scanning vibrometer is employed to test the ODS as well as natural frequencies of WT blades to testify the performance of the multiple damage detection method. Results show that the present method is effective for the detection of multi-damage in WT blades with a certain noise robustness.

The interaction between fluids and structures play an important role in number of fields. Important applications can be found in wind turbine blades, airplane wings, tall buildings, suspension bridges and biomechanics. The flow induced vibration (FIV) may affect negatively the operation and the response of the system. Flow induced vibrations in wind turbine blades is one of main considerations for the design of wind turbine, because aerodynamic loading causes blade to bend mostly in flap wise direction, and causes blade section to twist to create new fluid fields surrounding the blade. This interaction between aerodynamics and deformation of wind turbine blade may lead to flow induced vibrations. The aim of this research is to analyze the problem of FIV in wind turbine blade, due to the pressure field caused by a fluid flow. For this purpose, vertical axis wind turbine is analyzed using computational fluid dynamics and finite element analysis for the computation of vibratory stresses. Three dimensional flow analysis of vertical axis wind turbine (VAWT) blade is performed at different TSR ranges from 2.5 to 4.5. The aerodynamics results of CFD analysis shows that the maximum torque of 75 Nm is obtained at TSR 3.5. Finite element analysis (FEA) is then used for the computation of vibratory stresses. Carbon epoxy composite material with orthotropic properties is used as the blade material for FEA analysis. First one-way Fluid Structure Interaction (FSI) is conducted to determine stress field due to the torque on wind turbine blade. Next Modal analysis is performed to obtain the natural frequencies and corresponding mode shapes. Finally, the force response analysis of the structure is performed using ANSYS transient structural module under maximum unsteady wind torques which were computed using ANSYS Fluent. The outcome of the analysis showed that the three bending modes are the most critical modes for blade failure.

Design of 10 kW Horizontal-Axis Wind Turbine (HAWT) Blade and Aerodynamic Investigation Using Numerical Simulation

A Biomimetic Ultrasonic Whistle for Use as a Bat Deterrent on Wind Turbines

An influences of iced airfoils on aerodynamic and aeroacoustic properties were studied to predict of the wind turbine noise on icing state. In order to validate the aerodynamic performance, the experimental results and iced airfoils, which were studied by Jasinski et al. [“Wind turbine performance under icing state conditions,” AIAA Paper No. 97-0977, 1997], were used. Ice accretions on the two S809 wind turbine airfoils were predicted using the NASA LEWICE code. For analysis of boundary layer properties, the computational fluid dynamics was used when the Reynolds number is 1 × 106. To validate aerodynamic performances, lift coefficients were compared to the experimental result. The aeroacoustic analysis is estimated by summating the Turbulent inflow (TI) noise and the airfoil self-noise. The airfoil self-noise is obtained using aerodynamics data such as a boundary layer thickness. Semi-empirical method proposed by Brooks et al. [Airfoil Self-Noise and Prediction (NASA reference publication 1218, 1989)] was used. The TI noise is a dominant noise source because of a complicated shape of leading edge on the iced airfoil. For considering leading edge shapes, therefore, TI noise modeling proposed by Moriarty et al. [“Recent improvement of a semi-empirical aeroacoustic prediction code for wind turbines,” AIAA Paper 2004–3041, 2004; “Prediction of turbulent inflow and trailing-edge noise for wind turbines,” AIAA Paper 2005–2881, 2005] was used. As a result, lift coefficients of the iced airfoils matched well experimental data by Jasinski et al. The sound pressure level was increased 2–4 dB from the clean airfoils. The analysis of wind turbine blades on icing state was conducted using the same method. The NREL Phase VI rotor was used as the baseline. Ice accretions on the two wind turbine blades were predicted using the LEWICE code. The overall sound pressure level was increased up to 2.6 dB from the clean wind turbine blade.

To study the influence of blade rotation on the lightning attracting ability of wind turbine, the circular arc high voltage electrode with different radius is designed in this paper. Two 1:30 scaling wind turbines are symmetrical under the circular arc high voltage electrode. The blades of the wind turbine #2 remain upright and static, while the blades of wind turbine # 1 are at static with different angle and rotation with different speeds. The negative polarity 250/2500$\mu$s standard operating wave is applied to the high voltage electrode and the condition of lightning striking is observed by camera. The test results shew that in the 1m gap condition, the probability of lighting striking to the wind turbine #1 in rotation is smaller than that of when the wind turbine #1 is static, indicating that the rotation of blades reduced the lighting attracting ability of wind turbine. In the 2m and 4m gap, the probability of lighting striking to the wind turbine #1 under the rotation is smaller than that of when the wind turbine #1 is static, indicating that the rotation of blades strengthened the lighting attracting ability of wind turbine. According to the principle of discharge, the rotation of blades will strengthen the electric field of region of blade tip and reduce the electric field of outer region of blade tip, which will change the lightning discharge process. The results can be used as reference for wind protection.

This study presents to investigate the mechanical properties and thermal properties of horizontal and vertical axis wind turbine (VAWT) blade using finite element analysis (FEA) Ansys software. The efficiency of the wind turbine is based on the design of wind turbine blade (WTB) and material used. The fiber-reinforced plastics (composite materials) such as glass fiber, carbon fiber and epoxy are used for model of wind turbine blade. After modeling of wind turbine blade using standard software CATIA, imported into software ANSYS for determining the structural and thermal strength of the wind turbine blades. The stress distributions observed on the horizontal axis wind turbine blade due to the applied structural load and thermal load. The maximum stress occurs on the surfaces (near the fixed end of hub) of the horizontal axis wind turbine blade (HAWT), and the minimum stress occurs near the tip end of the blade. Due to the applied thermal condition (temperature) on the blades, the heat flux generated almost equal to both the HAWT blade and VAWT blade. Based on the FEA Ansys results, horizontal wind turbine blade produces better structural strength and thermal strength than vertical wind turbine blade.KeywordsWind turbine bladeFinite element analysis (ANSYS)Composite materialsStrength propertiesThermal properties

The roughness increase on horizontal axis wind turbine (HAWT) blade surface, especially on the leading edge, can lead to an aerodynamic performance degradation of blade and power output loss of HAWT, so roughness sensitivity is an important factor for the HAWT blade design. However, there is no criterion for evaluating roughness sensitivity of blade currently. In this paper, the performance influences of airfoil aerodynamic parameters were analyzed by the blade element momentum (BEM) method and 1.5 MW wind turbine blade. It showed that airfoil lift coefficient was the key parameter to the power output and axial thrust of HAWT. Moreover, the evaluation indicators of roughness sensitivity for the different spanwise airfoils of the pitch-regulated HAWT blade were proposed. Those respectively were the lift-to-drag ratio and lift coefficient without feedback system, the maximum lift-to-drag ratio and design lift coefficient with feedback system for the airfoils at outboard section of blade, and lift coefficient without feedback, maximum lift coefficient with feedback for the airfoils at other sections under the pitch-fixed and variable-speed operation. It is not necessary to consider the roughness when HWAT can be regulated to the rated power output by the pitch-regulated and invariable-speed operation.

Mitigation of edgewise vibrations in wind turbine blades by means of roller dampers

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.

Noise regulations in many countries are becoming extremely strict and wind turbine noise is thus becoming a barrier for further development of onshore wind turbines. Low noise wind turbine airfoil and blade design is an important technique for noise reduction. However, the flow situation of a wind turbine in wind farms is very complicated. In order to accurately model the noise generation and propagation from wind turbines in wind farms, it is urgent to develop a high-fidelity noise model to predict the noise features in complex situations. In the present study, we develop a flow-acoustic splitting technique where the wind turbine flow is calculated by using the in-house actuator line/LES/Navier-Stokes technique and the acoustics is obtained by solving the acoustic perturbation equations. In the flow solver, the wind turbine blades are modelled by rotating lines with body forces determined according to the local conditions and airfoil data. In the acoustic solver, the aeroacoustics is simulated by: (1) calculating the noise source using the improved engineering model (IBPM) based on the model developed by Brook, Pope and Marcolini (BPM); (2) introducing the noise source with an expected range of frequencies along the blade lines in the acoustic solver; (3) solving the acoustic perturbation equations with the introduced source and the source captured in the flow. The model can be used to study the prediction and propagation of low-frequency noise in complex situations. Noise generated by a wind turbine with and without yaw under wind shear and inflow turbulence will be presented in the paper.

In past few decades wind turbines are manufactured mainly by using standard components. Later, turbines were fabricated by using special components only. The best way to solve this is by using composite materials in wind turbine blades. Many of the composites are comprises of two materials. One material i.e., which binds together a bunch of fibres matrix (epoxy resin) and the second material (the reinforcement) adjacent these fibres. These days few researchers have aspired in utilizing the diversified applications of composite materials as the materials of the future. In this perspective wind turbine with three blades (Flax fibre) are designed and fabricated using hand-layup fabrication method and this process considers fiber in weight percentage of 5%, 10%, 15%, 20% and 25%. Moulds are prepared by using these combinations and undergone different tests like flexural, tensile and impact and the best suited combination of weight is used in turbine blade manufacturing. These turbine blade samples are used for understanding of different air velocities and different specifications of wind turbine such as power developed by wind turbine, power developed by wind, power co-efficient, speed of wind turbine are calculated and compared with existing aluminium material blades used in wind turbine.In past few decades wind turbines are manufactured mainly by using standard components. Later, turbines were fabricated by using special components only. The best way to solve this is by using composite materials in wind turbine blades. Many of the composites are comprises of two materials. One material i.e., which binds together a bunch of fibres matrix (epoxy resin) and the second material (the reinforcement) adjacent these fibres. These days few researchers have aspired in utilizing the diversified applications of composite materials as the materials of the future. In this perspective wind turbine with three blades (Flax fibre) are designed and fabricated using hand-layup fabrication method and this process considers fiber in weight percentage of 5%, 10%, 15%, 20% and 25%. Moulds are prepared by using these combinations and undergone different tests like flexural, tensile and impact and the best suited combination of weight is used in turbine blade manufacturing. These turbine blade samples are used fo...

Monitoring the blades of a wind turbine by using videogrammetry

An in-house aero-elastic vortex code, called MIRAS, is used to investigate the aerodynamic performance of winglets and sweep on horizontal-axis wind turbine (HAWT) blades in simple and complex inflow conditions. Previous studies using vortex codes applied to study winglets and blade sweep on HAWTs have typically not considered complex inflow conditions such as turbulent wind and shear. The reasons may include the absence of modeling capability, the computational cost associated with simulating long turbulent time series, and/or the computational cost associated with resolving the blade tips to a very fine level. A preliminary study is performed here, where the MIRAS code is applied on the NREL 5MW wind turbine with an arbitrary winglet shape and blade sweep. Results indicate that wind turbine blades with sweep or winglets might be better in performance compared to their straight blade counterparts.

The present paper investigates the effects of wind turbine nominal power limitation on the remaining useful life of turbine blades. It also looks at the economic impact of this limitation. In this context, the paper provides wind turbine owners and operators with an overview of how to potentially extend the remaining useful life of wind turbine blades and lays out the economic benefits that can be achieved via the modulation of nominal power. In investigating wind turbine blade damage, prior studies focused mainly on predictive models based on the 10 minutes SCADA data wind speed history, without however, trying to protract the remaining useful life of the blades. Only a handful of papers have explored the possibility of increasing the remaining useful life by adjusting the start-up and shutdown procedures with poor results. It would appear that wind turbine blade fatigue damage mainly increases when the wind turbine is in a power production regime, and the mechanical stresses associated with this regime are a function of the nominal power of the wind turbine. The present work therefore investigates the impacts of nominal power changes on both the remaining useful life of wind turbine blades and the economic value of the wind turbine in a bid to identify an optimal control mode. The wind turbine blade damage evaluation is based on 10 minutes SCADA data and the FAST simulation tool with the ultimate goal of providing wind turbine operators with an easy application. The damage evaluation is then applied considering different nominal power levels for the same wind turbine model in order to see the resulting impact on the remaining useful life. This project therefore takes a pioneering approach by proposing a remaining useful life optimization tool to wind turbine operators, in effect, a decision-making tool regarding which exploitation strategy to adopt.