Optimized Design of Bio-Inspired Wind Turbine Blades

To enhance the aerodynamic performance of wind turbine blades,this study proposes the adoption of a bionic airfoil inspired by the aerodynamic shape of an eagle.Based on the blade element theory,a non-uniform extraction method of blade elements is employed for the optimization design of the considered wind turbine blades.Moreover,Computational Fluid Dynamics(CFD)is used to determine the aerodynamic performances of the eagle airfoil and a NACA2412 airfoil,thereby demonstrating the superior aerodynamic performance of the former.Finally,a mathematical model for optimizing the design of wind turbine blades is introduced and a comparative analysis is conducted with respect to the aerodynamic performances of blades designed using a uniform extraction approach.It is found that the blades designed using non-uniform extraction exhibit better aerodynamic performance.

Functional design of wind turbine airfoils based on roughness sensitivity characteristics

To improve aerodynamic performance of wind turbine airfoils,the shape profile characteristic of the airfoil is investigated.Application of conformal transformation,one functional and integrated expression of wind turbine airfoils is presented.Using the boundary layer theory,the aerodynamic model with roughness of wind turbine airfoils is introduced by studying flow separation around the airfoil.Based on the shape expression and aerodynamic performance of airfoils,the function design of wind turbine airfoils is carried out that the maximum lift-drag ratio and low roughness sensitivity are designed objects.Three wind turbines airfoils with different thickness are gained which are used at tip part of blades.As an example,the aerodynamic performance of one designed airfoil with relative thickness of 15%is simulated in different conditions of clean surface,rough surface,laminar flow and turbulent flow.The comparison of aerodynamic performance between the designed airfoil and one popular NACA airfoil is completed which can verify the better performance of the designed airfoil and reliability of the designed method.

CFD-Based Performance Analysis and Experimental Investigation of Design Factors of Vertical Axis Wind Turbines under Low Wind Speed Conditions in Thailand

This paper presents effects of design factors on mechanical performance of Vertical Axis Wind Turbines (VAWTs), and an experimental investigation of optimal VAWT performance under low wind speed conditions in Thailand. Design factors include types of wind turbines, number of blades, types of materials, height-to-radius ratios, and design modifications. Potential VAWT models with different design factors are numerically analyzed within a virtual wind tunnel at various wind speeds by utilizing XflowTM?Computational Fluid Dynamics (CFD) software. The performance curves of each VAWT are obtained as plots of power coefficients against tip speed ratios. It is found that the type of wind turbine, number of blades, and height-to-radius ratio have significant effects on mechanical performance whereas types of materials result in shifts of operating speeds of VAWTs. Accordingly, an optimal VAWT prototype is developed to operate under actual low speed wind conditions. The performance curve from experimental results agrees with the CFD results. The proposed methodology can be used in the computer design of VAWTs to improve mechanical performance before physical fabrication.

Numerical investigation on the flow and power of small-sized multi-bladed straight Darrieus wind turbine

Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.

Performance Investigation of Three Combined Airfoils Bladed Small Scale Horizontal Axis wind Turbine by BEM and CFD Analysis

The present work is based on the comparative study between “Blade-Element- Momentum” (BEM) analysis and “Computational-Fluid-Dynamics” (CFD) analysis of small-scale horizontal axis wind turbine blade. In this study, the pitch is considered as fixed and rotor speed is variable. Firstly, the aerodynamic characteristics of three different specialized airfoils were analyzed to get optimum design parameters of wind turbine blade. Then BEM was performed with the application of the open source wind turbine design and performance computation software Q-Blade v0.6. After that, CFD simulation was done by Ansys CFX software. Here, k-ω “Shear-Stress-Transport” (SST) model was conducted for three-dimensional visualization of turbine performance. However, the best coefficient of performance was observed at 6o angle of attack. At this angle of attack, in the case of BEM, the highest coefficient of performance was 0.47 whereby CFD analysis, it was 0.43. Both studies showed good performance prediction which was a positive step to accelerate the continuous revolution in wind energy sector.

Criterion of aerodynamic performance of large-scale offshore horizontal axis wind turbines

With the background of offshore wind energy projects, this paper studies aerodynamic performance and geometric characteristics of large capacity wind turbine rotors （1 to 10 MW）, and the main characteristic parameters such as the rated wind speed, blade tip speed, and rotor solidity. We show that the essential criterion of a high- performance wind turbine is a highest possible annual usable energy pattern factor and a smallest possible dimension, capturing the maximum wind energy and producing the maximum annual power. The influence of the above-mentioned three parameters on the pattern factor and rotor geometry of wind turbine operated in China＇s offshore meteoro- logical environment is investigated. The variation patterns of aerodynamic and geometric parameters are obtained, analyzed, and compared with each other. The present method for aerodynamic analysis and its results can form a basis for evaluating aerodynamic performance of large-scale offshore wind turbine rotors.

The Design of Stall-Regulated Wind Turbine Blade for a Maximum Annual Energy Output and Minimum Cost of Energy Based on a Specific Wind Statistic

The design of a stall-regulated wind turbine to achieve a maximum annual energy output is still a formidable task for engineers. The design could be carried out using an average wind speed together with a standard statistical distribution such as a Weibull with k = 2.0. In this study a more elaborated design will be attempted by also considering the statistical bias as a design criterion. The wind data used in this study were collected from three areas of the Lamtakong weather station in Nakhonratchasima Provice, the Khaokoh weather station in Phetchaboon and the Sirindhorn dam weather station in Ubonratchathani, Thailand. The objective is to design a best aerodynamic configurations for the blade (chord, twist and pitch) using the same airfoil as that of NREL Phase VI wind turbine. Such design is carried out at a design wind speed point. Wind turbine blades were optimized for both maximum annual energy production and minimum cost of energy using a method that take into account aerodynamic and structural considerations. The work will be carried out by the program “SuWiTStat” which was developed by the authors and based on BEM Theory (Blade Element Momentum). Another side issue is the credibility of the Weibull statistic in representing the real wind measurement. This study uses a regression analysis to determine this issue.

周期性脉动源对风力机功率的影响

针对WindPACT1.5 MW机组,通过大涡模拟探究风轮5°仰角时周期性脉动源(仰角、塔影效应、偏航、风剪切)对风力机总功率的影响,并结合逆叶素动量理论,进一步分析功率与升力系数之间的联系。结果表明,仰角、塔影效应加仰角与偏航加仰角均使得风力机总功率产生“3P”的波动规律,而风剪切加仰角使得总功率产生“锯齿状”的高频率波动规律,其中偏航是总功率损失的主要因素,塔影效应是功率波动的主要因素,且发现升力系数波动规律与功率单周期内的波动规律相似。

改善惯性响应与一次调频的风电全直流系统协调控制策略

针对风电全直流系统并网给交流电网带来的系统惯量降低、调频能力不足等问题,提出一种改善惯性响应与一次调频的变系数风电全直流系统协调控制策略。在惯量响应方面,网侧换流站采用惯性同步控制,直流升压站采用恒变比控制,实现直流电容对电网的惯量支撑及直流低压侧的直流电压对交流系统频率的感知,在此基础上对直流风电机组(direct current wind turbine,DCWT)附加变虚拟惯性系数的虚拟惯量控制,使风电全直流系统在不同频率响应阶段具备不同的等效惯量。在一次调频方面,DCWT采用超速与变桨相结合的减载运行方式,通过变下垂控制来改变其有功出力,充分利用不同风速下的备用容量,使风电全直流系统更有效地参与一次调频。仿真算例表明,文中所提策略改善了风电全直流系统接入后电力系统的惯性响应及一次调频。

郁金香型垂直轴风力机的叶型性能研究

传统Savonius型(S型)直叶片风力机与城市景观适配度不高,为此郁金香型垂直轴风力机逐渐受到行业与用户的青睐。为探明传统S型直叶片与郁金香型垂直轴风力机气动性能差异以及叶片型线对郁金香型风力机的影响,本文采用3040型线和半圆形型线设计了郁金香型垂直轴风力机并开展了全尺寸三维数值模拟研究。结果发现:对于S型直叶片风力机,3040型线的最高功率系数相较于半圆型线高出约6%。相比于S型直叶片风力机,郁金香风力机半圆型线及3040型线的功率系数在各个叶尖速比下均有轻微下降。对郁金香风力机性能进行分析后发现:在叶片弦长较大的区域,3040型线的扭矩值略高于半圆型线;在叶片中弦长较小的区域,半圆型线的风力机扭矩值较高,性能更好;当叶片弦长下降时,相比于半圆型线风力机,3040型线风力机的扭矩值下降速度更快,整体呈现非线性关系。

基于离心机实验的海上风力机大直径单桩桩土作用研究

地基基础是海上风电结构所受载荷的最终承载者,针对中国沿海软弱超固结软土地基开展力学特性研究。通过离心模型试验方法对单桩基础形式的静力特性进行分析和对比。研究结果揭示通过离心模型试验模拟桩基础的有效性,该方法能准确捕捉现场地基的应力分布及桩与土体之间的相互作用特性。在软黏土环境中,针对不同直径的单桩进行的分析表明,其变形行为及桩土相互作用机制呈现出显著的差异性。规范中的p-y曲线不适用于中国近海土质,据试验结果提出地基无量纲水平抗力系数随埋深变化和与循环应力幅值相关的循环弱化因子计算模型。

海上风电装备产业基地生产设施设计

以某大型海上风电智能化装备产业园为例,概述风电产品的主要参数、风电机组和叶片的生产能力规划与特点,并据此分析其工艺流程和生产设施,拟定机组总装车间和叶片制作车间的工艺区划方案。在此基础上,基于工时计算确定工序工位数,结合工位尺寸形成车间的工艺布置,完成生产设施设计,为我国海上风电装备产业基地的规划建设提供参考。

基于自适应桨距角控制策略的风电机组发电性能优化方法

针对长期服役风电机组的叶片表面粗糙度增加、叶片桨距角传感器测量误差累积等原因导致的风电机组发电性能下降问题,提出一种基于自适应桨距角控制策略的风电机组发电性能优化方法。首先分别以二次多项式、高斯函数和三角函数这3种数据拟合方法进行叶片桨距角补偿值和风能利用系数函数拟合,并以离散度变化敏感性、样本量变化敏感性、运算周期变化敏感性作为拟合函数的评价指标;然后设计了评价指标定量计算方法,用于评价各种数据拟合方法的拟合效果;最后,以长期服役的某2 MW直驱型风电机组为例,研究其执行自适应桨距角控制策略后的发电性能。研究结果显示:1)高斯函数是比二次多项式、三角函数更好的数据拟合方法,原始数据经过核密度估计函数曲线筛选后拟合函数最大值具有更好的一致性。2)长期服役的某2 MW直驱型风电机组执行自适应桨距角控制策略后,测算得到的年发电量较执行该策略前提升了1.3%,提高了90.4 MWh,表明自适应桨距角控制策略能提升风电机组发电性能。

风电机组辅助用电容量测试与分析

本文主要针对风力发电机组辅助用电设备目前行业尚没有对应的设计规范的情况,通过风机控制器记录辅助设备的运行情况,通过对风力发电机组辅助用电设备的测试数据进行分析,掌握风力发电机组辅助用电的主要运行设备的启动和运行情况,不同设备之间的错峰运行规律,总结风力发电机组辅助用电选型经验系数,为风力发电机组辅助变压器容量计算提供依据。

基于子带处理与相关系数的风电机组功率异常波动检测

风电机组功率的周期性异常波动容易引起电网的低频振荡,威胁电网安全;而风电机组功率信号是一种非线性、非平稳信号,其异常波动频率存在不确定性,为异常波动特征的提取与检测带来困难。为此,文章提出一种基于子带处理与相关系数的风电机组功率异常波动检测方法。其首先将原始功率信号通过高通滤波器去除趋势项,然后采用子带处理滤波器组进行信号分解,得到一系列子带信号;将去除趋势项后的功率信号与各子带信号分别计算互相关系数,并根据互相关系数实现周期性异常波动所在子带的定位及子带筛选;基于筛选所得子带信号进行信号重构得到高信噪比重构信号;采用峰值检波与自相关分析相结合的检测方法,识别重构信号中特定幅值周期性异常波动发生时段,从而达到风电机组功率信号周期性异常波动检测的目的。现场数据测试结果表明,对于0.06 Hz、0.32 Hz等不同频率的功率周期性异常波动,该方法能够准确识别其所在子带及特征。

基于荷载组合的海上浮式风机中外规范探讨

目前我国海上浮式风机的设计规范仍处于起步探索阶段,本文旨在推动我国相关标准规范进一步建立健全。本文选取了4部具有代表性的相关设计规范和标准,对结构设计中关于工况、荷载组合的相关规定进行了介绍,给出了各规范对我国海上浮式风机工程设计的适用性和可参考性。在此基础上,提出了发展我国海上浮式风机标准规范的建议。

大功率风力发电机组铸造主轴的结构设计与强度分析

针对某大功率风力发电机组主轴材料利用率低、生产周期长、成本高的问题,将主轴生产工艺由锻造改为铸造,对其薄弱位置进行结构优化设计,并进行极限强度和疲劳强度分析。通过极限强度和疲劳强度分析可知,铸造主轴的Von Mises应力和疲劳损伤均满足设计要求。研究表明,铸造主轴比锻造主轴单台节约成本21万元,大幅度降低生产成本,产生良好的经济效益,为大功率风力发电机组铸造主轴的结构设计与强度分析提供了参考。

CFD analysis of performance improvement of the Savonius water turbine by using an impinging jet duct design

The majority of research on water turbines focuses on design improvement of large-scale hydrokinetic turbines for power generation, which may have delayed the utilization of kinetic energy contained in rivers and canals. The aim of this paper is to improve the efficiency of a two bladed Savonius type cross-flow hydrokinetic turbine, which can be used as an energy converter to harness free-stream kinetic energy of water. An impinging jet duct design is presented for improving performance of the Savonius turbine in wind application as seen from literature. The performance of the modified turbine is evaluated using CFD software Fluent, and is compared with that of a simple two bladed Savonius water turbine and some of the prominent literature designs of the Savonius turbine. It is shown that the present design exhibits improved performance compared to the selected designs of the Savonius turbine.Further an insight of the improved performance of the modified turbine is also obtained from flow physics study.

Experimental Investigation of Performance of the Wind Turbine with the Flanged-Diffuser Shroud in Sinusoidally Oscillating and Fluctuating Velocity Flows

The wind turbine with a flanged-diffuser shroud—so called “wind-lens turbine”—is developed as one of high performance wind turbines by Ohya et al. In this paper, the wind turbine performance is investigated for both steady and unsteady winds. The compact-type wind lens turbine shows higher efficiency than the only rotor wind turbine. Also, the flow structure around the compact-type wind turbine is made clear by CFD and PIV in steady wind. Furthermore, the performances of the only rotor and the compact-type wind-lens turbines for unsteady wind are experimentally and numerically investigated. Experimental and numerical results are presented to demonstrate the dependence of frequency of the harmonic oscillating velocity wind on power coefficient. Consequently, the compact-type wind-lens turbine show better performance than the only rotor one in sinusoidally oscillating velocity wind. Furthermore, the numerical estimation can predict the power coefficient in the oscillating flows to an accuracy of 94% to 102%. In addition, the dependence of the turbine performance on turbulent intensity and vortex scale of natural fluctuating wind is presented.

Effect of blade pitch angle on aerodynamic performance of straight-bladed vertical axis wind turbine

Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.