【作者】 张毅；

【导师】 蒋兴良；

【作者基本信息】 重庆大学 ， 电气工程， 2018， 硕士

【摘要】 近年来,随着国际社会对能源转型发展和大气污染防治问题的重视,全球风电产业发展迅速。但南方高湿低温地区风电场冬季经常出现风机叶片覆冰问题,风机叶片覆冰其气动性能急剧下降,严重降低了风力发电机组的电力输出,导致停机,且对风电场的安全稳定运行带来很大的隐患。目前风机叶片覆冰问题的研究不多,主要是由于缺少风力发电机现场覆冰试验平台,且现场风力发电机覆冰试验与数值模拟存在较大的差异。因此,通过风机叶片覆冰试验结合数值模拟方法,可以更好的研究风机叶片的覆冰增长过程,分析风机叶片覆冰增长的影响因素,对于风电场的防冰除冰和安全运行具有重要的工程实用价值。论文主要针对NE-100型水平轴风力机叶片的覆冰进行了数值仿真和人工覆冰试验。建立了风机叶片二维翼型几何模型,计算了空气中过冷却水滴的运动状况,得到不同环境参数下的风机叶片表面过冷却水滴的碰撞系数和冻结系数,求解得到风机叶片的覆冰厚度,绘制了风机叶片覆冰形态。在人工气候室内进行了风机叶片的覆冰试验,分析了相关环境参数对风机叶片覆冰质量及覆冰厚度的影响。主要研究工作及成果如下:(1)建立了风机叶片覆冰的数学物理模型。对风机叶片叶尖处截面翼型建立二维几何模型,利用Fluent软件计算风机叶片空气绕流场,得到过冷却水滴的运动轨迹,分析水滴的运动情况。结果表明:流场中过冷却水滴主要撞击在风机叶片前缘及迎风面。(2)通过基于拉格朗日法计算得到风机叶片水滴碰撞系数的分布规律。计算结果表明:来流合速度和水滴中值直径(MVD,Median Volume Diameter)的增大都会使水滴碰撞系数增大;来流合速度越大,水滴的碰撞区域由迎风面向背风面移动;MVD越大,风机叶片表面水滴的碰撞区域越大。(3)根据Messinger积冰热力学模型,求解叶片覆冰热力学平衡方程,计算了风机叶片表面水滴冻结系数的分布规律。计算结果表明:风机叶片驻点处水滴冻结系数最小,且呈现沿叶片迎风面和背风面逐渐增大的趋势;在部分区域水滴冻结系数达到饱和值1,说明此时覆冰类型为雾凇覆冰;环境温度降低、液态水含量(LWC,Liquid Water Content)及来流合速度变小都会使水滴冻结系数增大。(4)基于上文风机叶片表面水滴碰撞系数和冻结系数的计算,计算出风机叶片的覆冰厚度,绘制出风机叶片的覆冰冰形。计算结果表明:来流合速度越大、环境温度越低及液态水含量越高,风机叶片表面的覆冰厚度越大。(5)在人工气候室内进行的风机覆冰试验研究了环境参数对风机叶片覆冰的影响,实验结果表明:风机叶片覆冰主要集中在叶尖处;叶根处覆冰较少且受环境因素影响变化不大;从叶根到叶尖处,覆冰质量和覆冰厚度逐渐增加;风速越大、液态水含量越高及试验温度越低,风机叶片覆冰质量及覆冰厚度越大。(6)对比了覆冰试验和数值仿真得到的风机叶片覆冰厚度,得出结论:考虑到覆冰试验未冻结水沿叶片流动以及更短时间内停机的影响,数值计算得到的风机叶片覆冰厚度更大。更多还原

【Abstract】 In recent years,with the international community’s emphasis on energy transformation development and prevention and control of air pollution,the global wind power industry has developed rapidly.However,wind farms in the high-humidity and low-temperature areas in the south often have problems with wind turbine blade icing in winter,the aerodynamic performance of wind turbine blades is drastically reduced,which seriously reduces the power output of wind turbines,resulting in downtime,and brings great hidden dangers to the safe and stable operation of wind farms.At present,there are not many researches on the problem of ice coating on wind turbine blades.a few studies are numerical simulation analysis,but the simulation analysis and the actual operation of the wind farm are quite different.Therefore,through the fan blade ice coating test combined with the numerical simulation method,the ice coating growth process of the fan blade can be better studied,and the influencing factors of the fan blade ice coating growth are analyzed.It is important for the wind farm to prevent ice and deicing and safe operation.The paper mainly carried out numerical simulation and artificial ice coating test on the ice coating of NE-100 horizontal axis wind turbine blades.The paper establishes the two-dimensional airfoil geometry model of thewind turbine blade and studies the motion process of the supercooled water droplets.The collision coefficient and freezing coefficient of the water droplets on the wind turbine blade surface under different environmental parameters are calculated.The ice thickness of the wind turbine blade is obtained and the ice shape of wind turbine blades are drawn.The ice coating test of wind turbine blades was carried out in the artificial climate chamber,and the influence of relevant environmental parameters on the ice coating weight and ice thickness of the wind turbine blades was analyzed.The main research work and results are as follows:(1)A mathematical physical model of wind turbine blade icing is established.A two-dimensional geometric model is established for the airfoil at the blade tip of the wind turbine blade.The flow field of the fan blade air is calculated by Fluent software,and the motion track of the supercooled water droplet is obtained,and the movement of the water droplet is analyzed.The results show that the supercooled water droplets in the flow field mainly impact on the leading edge and the windward side of the fan blade.(2)The distribution law of the water droplet collision efficiency of the fan blade is calculated based on the Lagrangian method.The calculation results show that the increase of the flow velocity and MVD will increase the collision coefficiency of water droplets.The larger the flow velocity,the collision zone of water droplets moves from the windward face to the leeward surface;the larger the MVD,the collision zone of water droplets on the fan blade surface is bigger.(3)According to the Messinger ice accretion thermodynamic model,the thermodynamic equilibrium equation of blade ice coating is solved,and the distribution law of water droplet freezing fraction on the wind turbine blade surface is calculated.The calculation results show that the freezing fraction of water droplets at the stagnation point of the fan blade is the smallest,and it tends to increase along the windward and leeward surfaces of the blade.In some areas,the freezing fraction of water droplets reaches a saturation value of 1,indicating that the ice coating type is rime ice.The decrease in ambient temperature,liquid water content and the incoming flow rate will increase the freezing fraction of water droplets.(4)Based on the calculation of the water droplet collision coefficiency and the freezing fraction of the wind turbine blade,the ice thickness of the wind turbine blade is calculated,and the ice shape of the fan blade is drawn.The calculation results show that the greater the flow velocity,the lower the ambient temperature and the higher the liquid water content,the greater the thickness of the ice on the surface of the wind turbine blade.(5)The effect of environmental parameters on the ice coating of wind turbine blades was studied in an artificial climate chamber.The experimental results show that the ice coating on the wind turbine blade is mainly concentrated at the tip of the blade;the ice at the blade root is less covered with ice and is not affected by environmental factors;the ice weight and ice thickness gradually increase from the root to the tip of the blade;the greater the flow velocity,the larger the liquid water content and the lower the test temperature,the greater the ice coating weight and the thickness of the ice coating.(6)Comparing the ice thickness of the wind trurbine blade obtained by the ice test and the numerical simulation,it is concluded that considering the effect of the ice-free test on the flow of unfrozen water along the blade and the shutdown in a shorter time,the thickness of the wind turbine blade obtained by the numerical calculation is larger.更多还原