水平轴风力机叶片翼型结冰的数值模拟

通过计算流体力学(CFD)的方法对水平轴风力机桨叶翼型的霜状积冰进行了数值模拟。模拟采用四阶龙格-库塔法求解水滴运动轨迹,假定水滴在与叶片相碰撞的点处完全凝结,并且冰沿着翼型表面法向方向增长,通过模拟得到了某风力机厂家提供翼型在不同时间段叶片表面结冰后形成的冰形,同时利用FLUENT软件模拟了风力机叶片翼型周围流场的变化,并与结冰前该翼型的气动性能进行了对比。研究结果表明与干净翼型相比,在模拟气象条件下的结冰翼型的最大升力系数大约减少了27%,阻力系数增加了约38%,失速攻角降低了4°。根据模拟可以认为,结冰后翼型提前进入失速区是造成桨叶气动性能恶化的主要原因。     

风力机叶片结冰水滴收集系数计算

针对风力机叶片结冰问题,采用欧拉两相流模型和FLUENT用户自定义函数(user defined function,UDF)计算NACA64618翼型/叶片的水滴收集系数。结果表明:水滴主要撞击在翼型前缘小范围内。随着攻角增大,水滴撞击极限往翼型压力面移动。受三维效应的影响,叶尖区域水滴收集系数急剧减小,减小量最大可达59.6%。     

水平轴风力机叶片翼型流场的数值模拟

为了直观形象地探讨水平轴风力机叶片翼型的气动特性,利用计算流体力学软件FLUENT对水平轴风力机叶片常用翼型NACA63425流场进行了数值模拟,得出了翼型NA-CA63425在不同来流攻角下的升力系数、阻力系数、升阻比和不同流攻角下的流场流线图和翼型表面的压力分布。根据模拟结果对不同攻角下尾迹漩涡分离流动进行了分析和比较,得出该翼型气动特性随攻角的变化规律。     

叶片副翼摆角对两段式翼型气动性能的影响

以Spalart-Allmaras(S-A)湍流模型为计算模型,对风力机叶片NACA0018翼型在副翼摆角分别为0°、5°、10°和15°下的流体流动情况进行数值模拟,分析不同攻角下带副翼翼型上升阻力性能曲线以及翼型表面压力分布云图和流场流线图,研究不同摆角对带副翼翼型的空气动力学性能的影响。结果表明:相同攻角时,翼型的升力系数随着副翼摆角的增大而减小;副翼摆角的增大可以增大翼型的失速攻角,改善翼型周围流体的流动状况,提高翼型周围特别是副翼周围流体流动稳定性,抑制流动分离涡的形成。     

垂直轴风力机非对称翼型叶片变攻角方法

分析了H型垂直轴风力机非对称翼型叶片在一定雷诺数下的升力系数和阻力系数的变化,给出了叶片攻角的合理变化范围。通过分析风轮旋转一周叶片攻角的变化,给出了不同叶尖速比下叶片攻角随其方位角变化的规律。利用Origin软件计算出上下风区叶片的安装角与攻角的对应关系,并确定合适的安装角。分析表明,通过改变风轮叶片的安装角来调整叶片的攻角,能使风力机始终保持较高的功率输出。     

基于Fluent的风力机叶片翼型气动性能数值研究

为了对风力机叶片翼型特性进行研究,通过Fluent软件对NACA4412翼型的不可压缩流动特征参数进行数值仿真研究。计算迭代得到翼型在0°~20°攻角下的升阻力系数,描述了各气动特性变化关系规律,分析了不同攻角下压力和速度分布云图。结果表明:随着攻角的增大,升阻力系数均增大,升阻比在4°~6°时达到最佳值,翼型左右两侧的高压区向翼型下表面移动,上部低压区域向翼型前端移动,翼型上部高速部分往前缘移动,气动绕流的分离点位置前移,为风力机叶片气动性能分析和叶片位置铺层提供重要参考。     

直线翼垂直轴风力机静态叶片结冰的观测与分析

设计制作了采用NACA0015翼型的直线翼垂直轴风力机叶片,安装于寒冷地区的室外.冬季,对雨雪等在静止叶片表面的附着情况进行了现场观测.将获得到的叶片表面结霜和结冰(霜状冰和瘤状冰)的观测结果与温度、湿度、风速和风向等气象条件进行了对比分析,研究了静止叶片表面结霜和结冰的产生机理与气象条件的影响关系.针对翼型表面瘤状结冰情况下翼型改变前后的静态升阻力系数进行了数值模拟计算,分析了翼型改变对升阻力特性和静态特性的影响.     

基于FLUENT的风力机叶片翼型NREL S809覆冰的数值模拟

对经典风力机叶片翼型NREL S809的覆冰过程和翼型覆冰前后的气动性能进行了研究。利用FLUENT软件自带的离散相模型DPM及用户自定义函数UDF,求解出翼型表面的水滴运动轨迹方程、水滴的撞击极限和局部收集系数;选用经典的Messinger积冰传热模型计算积冰厚度,得到积冰形状;并分析在不同的攻角下,洁净翼型与覆冰翼型的气动性能。研究指出,覆冰导致翼型的气动性能发生畸变,升力系数下降,阻力系数上升,升阻比减小,升阻比最大降幅达到85.97%;覆冰后的翼型会提前进入失速区,破坏了翼型原有的流线,会造成翼型空气动力特性恶化。     

小型水平轴风力机导流罩结冰的风洞试验

利用风洞试验对小型水平轴风力机的导流罩结冰现象进行了测试和分析。试验在冬季进行,在风洞吹出口附近安装了水滴流量可控的喷水装置来模拟结冰环境。试验中的水滴流量分别为0.5,1 L/min,风速为4～12 m/s,间隔1 m/s。在相同水滴流量情况下,随着风速的增加,导流罩的结冰率呈增大的趋势;在同一风速条件下,大水滴流量下导流罩的结冰率比小水滴流量的大,而且这种趋势在低风速时较为明显。     

风力机翼型前缘表面粗糙度对气动性能影响

研究了目前在风力机叶片设计中常用的FFA-W3翼型设计的叶片上前缘表面局部增加表面粗糙度条件下对叶片气动性能的影响.在探讨翼型表面前缘粗糙度的形成机理的基础上,设计了在风洞中实现研究局部增加前缘表面粗糙度对翼型性能影响的实验方案,测量了相关参数并分析了实验结果.实验结果表明,在叶片压力面前缘粗糙度的增加对翼型的空气动力学性能有一定影响.     

Effect of icing roughness on wind turbine power production

The objective of this work is a quantitative analysis of power loss of a representative 1.5‐MW wind turbine subject to various icing conditions. Aerodynamic performance data are measured using a combination of ice accretion experiments and wind tunnel tests. Atmospheric icing conditions varying in static temperature, droplet diameter and liquid water content are generated in an icing facility to simulate a 45‐min icing event on a DU 93‐W‐210 airfoil at flow conditions pertinent to 80% blade span on a 1.5‐MW wind turbine. Iced airfoil shapes are molded for preservation and casted for subsequent wind tunnel testing. In general, ice shapes are similar in 2D profile, but vary in 3D surface roughness elements and in the ice impingement length. Both roughness heights and roughness impingement zones are measured. A 16% loss of airfoil lift at operational angle of attack is observed for freezing fog conditions. Airfoil drag increases by 190% at temperatures near 0° C, 145% near 10° C and 80% near 20° C. For a freezing drizzle icing condition, lift loss and drag rise are more severe at 25% and 220%, respectively. An analysis of the wind turbine aerodynamic loads in Region II leads to power losses ranging from 16% to 22% for freezing fog conditions and 26% for a freezing drizzle condition. Differences in power loss between icing conditions are correlated to variance in temperature, ice surface roughness and ice impingement length. Some potential control strategies are discussed for wind turbine operators attempting to minimize revenue loss in cold‐climate regions. Copyright © 2016 John Wiley & Sons, Ltd.     

The relationship between chord length and rime icing on wind turbines

Numerical simulations of ice accumulation on four different wind turbine blade profiles, from 450 kW, 600 kW, 1 MW and 2 MW, fixed speed, stall controlled, wind turbines, were performed to determine how wind turbine size affects atmospheric icing. The simulations indicate that dry rime icing is less severe for larger wind turbines both in terms of local ice mass and in terms of relative ice thickness. Copyright © 2009 John Wiley & Sons, Ltd.     

叶片附着物对直线翼垂直轴风力机性能的影响

采用黏土作为附着物模拟了直线翼垂直轴风力机叶片表面前缘的结冰情况,并通过风洞试验测试分析了附着物对自行设计制作的直线翼垂直轴风力机模型转速和功率特性的影响.结果表明:附着物的存在降低了风力机的稳定转数、减少了输出功率,且随着附着质量的增加和风速的增大,影响效果越明显.通过将同等质量的黏土附着在叶表和嵌入叶片内的对比试验表明:在本试验条件下,附着物质量轻时,附着质量与翼型变化对风力机性能的影响基本为同等程度;随着附着物质量的增加,附着质量对风力机性能的影响占居主导地位.     

风力机叶片覆冰状态监测基准值与分级诊断标准研究

以2 MW风力机为研究对象,基于实际风力机状态(SCADA)系统大数据,选取叶片正常状态和覆冰状态下的风速、功率、桨距角和偏航角数据,采用核密度-均值数据处理方法,得到叶片覆冰状态监测基准值及其定量表达式。同时,根据叶片不同覆冰时期桨距角和功率值随风速的变化情况,提出叶片覆冰状态分级诊断标准。应用结果表明,根据桨距角随风速的变化情况可判断在叶片覆冰过程中机组最大功率追踪情况以及气动性能损失情况,根据风速-功率值分布情况可较准确地判别叶片的覆冰状态。     

Predictions of ice formations on wind turbine blades and power production losses due to icing

Prediction of ice shapes on a wind turbine blade makes it possible to estimate the power production losses due to icing. Ice accretion on wind turbine blades is responsible for a significant increase in aerodynamic drag and decrease in aerodynamic lift and may even cause premature flow separation. All these events create power losses and the amount of power loss depends on the severity of icing and the turbine blade profile. The role of critical parameters such as wind speed, temperature, liquid water content on the ice shape, and size is analyzed using an ice accretion prediction methodology coupled with a blade element momentum tool. The predicted ice shapes on various airfoil profiles are validated against the available experimental and numerical data in the literature. The error in predicted rime and glime ice volumes and the maximum ice thicknesses varies between 3% and 25% in comparison with the experimental data depending on the ice type. The current study presents an efficient and accurate numerical methodology to perform an investigation for ice‐induced power losses under various icing conditions on horizontal axis wind turbines. The novelty of the present work resides in a unified and coupled approach that deals with the ice accretion prediction and performance analysis of iced wind turbines. Sectional ice profiles are first predicted along the blade span, where the concurrence of both rime and glaze ice formations may be observed. The power loss is then evaluated under the varying ice profiles along the blade. It is shown that the tool developed may effectively be used in the prediction of power production losses of wind turbines at representative atmospheric icing conditions.     

基于WD-LSTM的风电机组叶片结冰状态评测

为有效识别叶片结冰状态,尽早采取除冰措施,提出基于小波去噪的长短期记忆神经网络（WD-LSTM）的评测方法。首先基于过采样与欠采样相结合的方法解决SCADA系统数据中的类别不平衡问题,通过对叶片结冰相关的26项指标进行分析,并从结冰机理和数据探索的角度筛选特征量,小波去噪处理后建立WD-LSTM模型,进一步完成模型的训练和测试。分别以15号和21号风电机组为例进行模型验证,通过与LSTM、概率神经网络（PNN）模型和BP神经网络模型进行对比。结果表明,WD-LSTM方法在风电机组叶片结冰评测中的准确率可达98%,优于其他方法。     

Wind turbine aerodynamic response under atmospheric icing conditions

This article deals with the atmospheric ice accumulation on wind turbine blades and its effect on the aerodynamic performance and structural response. The role of eight atmospheric and system parameters on the ice accretion profiles was estimated using the 2D ice accumulation software lewice Twenty‐four hours of icing, with time varying wind speed and atmospheric icing conditions, was simulated on a rotor. Computational fluid dynamics code, FLUENT, was used to estimate the aerodynamic coefficients of the blade after icing. The results were also validated against wind tunnel measurements performed at LM Wind Power using a NACA64618 airfoil. The effects of changes in geometry and surface roughness are considered in the simulation. A blade element momentum code WT‐Perf is then used to quantify the degradation in performance curves. The dynamic responses of the wind turbine under normal and iced conditions were simulated with the wind turbine aeroelastic code HAWC2. The results show different behaviors below and above rated wind speeds. In below rated wind speed, for a 5 MW virtual NREL wind turbine, power loss up to 35% is observed, and the rated power is shifted from wind speed of 11 to 19 m s^?1. However, the thrust of the iced rotor in below rated wind speed is smaller than the clean rotor up to 14%, but after rated wind speed, it is up to 40% bigger than the clean rotor. Finally, it is briefly indicated how the results of this paper can be used for condition monitoring and ice detection. Copyright © 2012 John Wiley & Sons, Ltd.     

Quantitative detection method for icing of horizontal‐axis wind turbines

Icing seriously endangers the operational safety of wind turbines, and there has been a lack of research on the quantitative detection and early warning of the icing distribution on a blade. In order to address the present state and specific engineering problems of wind turbines, a method based on external sensor installation is proposed for quantitatively monitoring the icing distribution on a blade through numerical simulation and sensor detection technology. Field tests were performed on 1.5 and 2.0 MW wind turbines in icy weather. The detected distribution and thickness of the blade icing showed good agreement with the field results, which verifies the effectiveness of the detection method. The error between the detected and real ice thicknesses was approximately 20%, which breaks through the limitations of previous qualitative monitoring, and the error for specific ice formations on the blade was within the acceptable range. This new monitoring method can provide a reference for wind turbine icing detection and technical support for the efficient design and effective operation of icing protection facilities.     

Wind turbine performance under icing conditions

The wind energy market is in full growth in Quebec but technical difficulties due to cold climate conditions have occurred for most of the existing projects. Thus, icing simulations were carried out on a 0.2 m NACA 63 415 blade profile in the refrigerated wind tunnel of the Anti‐icing Materials International Laboratory (AMIL). The shapes and masses of the ice deposits were measured, as well as the lift and drag forces of the iced profiles. Scaling was carried out based on the 1.8 MW–Vestas V80 wind turbine technical data, for three different radial positions and two in‐fog icing conditions measured at the Murdochville wind farm in the Gaspé Peninsula. For both icing events, the mass of ice accumulated on the blade profile increased with an increase in the radial position. In wet regime testing (first icing event), glaze formed mostly near the leading edge and on the pressure side. It also accumulated by run‐off on the trailing edge of the outer half of the blade. In dry‐regime testing (second icing event), rime mostly accreted on the leading edge and formed horns. For both icing events, when glaze or rime accreted on the blade profile, lift decreased and drag increased. A load calculation using the blade element theory shows that drag force on the entire blade becomes too large compared to lift, leading to a negative torque and the stop of the wind turbine. Torque reduction is more significant on the outer third of the blade. Setting up a de‐icing system only on the outer part of the blade would enable significant decrease of heating energy costs. Copyright © 2007 John Wiley & Sons, Ltd.     

风力机叶片气热除冰技术研究现状与展望

风电机组叶片结冰给风电场的运行安全和发电效益带来双重困扰,因此迫切需要对结冰较严重的风力机进行除冰技术改造。本文首先对风力机叶片4种除冰技术进行对比,并对其原理、适用性和可靠性进行了分析和比较。重点阐述了现有气热除冰技术的4种技术路线及方案,讨论了气热除冰技术方案的经济效益和热传递效果,并对气热除冰存在的主要问题进行说明。系统论述了该技术在能量利用效率和除冰效率方面仍具有极大的改进和提升空间,提出了气热除冰设备在标准化、控制系统轻量化、系统效率提升等方面的一些设想和展望。