水平轴风力机尾流特性的三维PIV风洞试验研究

发布时间：2018-05-23 07:30

本文选题：风力机 + 粒子图像测速技术　；参考：《武汉大学》2014年博士论文

【摘要】：作为可再生清洁能源中的一种,风力发电技术在世界范围内发展迅速,得到了愈来愈多的重视。大容量的风电机组及大规模风电场已成为了当今风能开发的主流,使得风电场中风力机组优化布置的重要性日益突显,而尾流效应就是其中主要的影响因素之一。风力机的尾流不仅对下游风力机的出力产生影响,降低下游风力机的发电量,同时,尾流区受叶尖漩涡影响,流场湍流强度加剧,表现为作用于风力机叶片上的空气荷载增加,会引起风力机的结构疲劳损坏,降低使用寿命,均直接关系到风电场的经济效益。为了减少或避免风力机尾流效应的影响,首先必须掌握风力机的尾流流场特性,对其进行正确的认识和描述。目前,大多数的分析及预估水平轴风力机尾流特性的方法都基于过多的假设,无法准确描述风力机尾流的三维流场特性和叶尖涡的演变及影响。从长远的角度来看,需要对水平轴风力机的尾流流场结构进行详细的试验研究,以形成更加完善的尾流理论体系；另一方面,对提高风力机的气动特性计算水平和风电场的流场分析水平,以更合理地布置风力机组起到重要作用,进一步提高风电场出力的预测精度。因此,对风力机尾流流场特性的研究十分必要和紧迫。本文通过理论分析和试验观测相结合的方法,利用三维粒子图像测速技术,开展了水平轴风力机尾流流场的风洞试验研究,具体的工作内容及研究成果如下： (1)在试验的前期准备工作中,进行了风洞试验段流场品质的评估。利用热线风速仪,探讨了空风洞流场的均匀性和稳定性,进而分析了适合于风力机尾流测量的风洞试验段范围,并为模型风力机尺寸大小的确定提供了参考,进一步减少因风洞环境的不稳定性造成的测量误差。 (2)介绍了试验所需的模型风力机的设计过程。基于叶素—动量理论,利用Wilson设计理论,通过MATLAB编程工具,对模型风力机的叶片进行了优化设计,最后进行生产制作,确定了本试验所采用的模型风力机。 (3)在风洞中开展了模型风力机尾流流场的试验观测研究。利用(2)中设计的模型风力机,在两个尖速比工况下,通过三维粒子图像测速技术,捕获了高分辨率的、三维瞬态的尾流流场信息,揭示了完整的风力机叶尖涡的发展及湮灭过程。经分析,得到了尾流速度场分布和叶尖涡运动的相关性规律。叶尖涡从叶片叶尖脱落后,在向下游运动的过程中,其螺旋状运动形态阻碍了尾流区内部的速度恢复,在风力机后方形成了一个轴向速度亏损区,该区域延伸至叶尖涡“交替跳跃”位置处。此后,叶尖涡耗散,其轨迹的屏蔽作用开始减弱,在周围流场的动能补给下,尾流区内的轴向速度逐渐恢复。 (4)利用试验数据,对目前工程上应用较为广泛的尾流数学计算模型进行了对比验证。分析的结果显示,这些模型由于存在不同的假设和简化,与试验数据的相符程度各不相同,其精度还有待提高。 (5)针对现有尾流计算模型的不足,在试验数据的基础上,对风力机尾流射流模型进行了修正。通过对试验结果的分析,提出了基于叶尖涡“交替跳跃”现象的风力机近、远尾流区的分区标准,并推导了近尾流区长度的计算公式。将风力机近尾流区的流场特征与射流理论相结合,修正了尾流射流模型,进而提高了尾流计算的精度。通过本文的研究,揭示了水平轴风力机尾流流场的物理机理,明确了尾流分区的标准,改善了尾流射流模型的计算精度,使之更适用于风电场尾流效应的评估。
[Abstract]:As one of the renewable clean energy sources , wind power generation technology has developed rapidly in the world . The large - capacity wind turbine unit and large - scale wind farm have become the main factors of wind energy development . The wake effect is one of the main influencing factors . The wake flow of the wind turbine not only affects the output of the downstream wind turbine , but also increases the turbulence intensity of the flow field .

In order to reduce or avoid the influence of wind turbine wake effect , it is necessary to understand and describe the characteristics of wake flow field of wind turbine . At present , most of the methods for analyzing and estimating wake characteristics of horizontal axis wind turbine are based on too many assumptions , which can not accurately describe the three - dimensional flow field characteristics of wind turbine wake and the influence of tip vortex .
On the other hand , it is necessary and urgent to study the characteristics of wind turbine wake flow field by improving the calculation level of aerodynamic characteristics of wind turbine and the flow field analysis level of wind farm .

Through the combination of theoretical analysis and experimental observation , the wind tunnel test of the wake flow field of a horizontal axis wind turbine is carried out by using the three - dimensional particle image velocity measurement technology , and the specific work contents and the research results are as follows :

( 1 ) In the pre - preparation work of the test , the flow field quality of the wind tunnel test section is evaluated . The uniformity and stability of the flow field in the air tunnel are discussed by using the hot wire anemometer , and the range of the wind tunnel test section suitable for the wind turbine wake measurement is analyzed , and the reference is provided for the determination of the size of the model wind turbine , and the measurement error caused by the instability of the wind tunnel environment is further reduced .

( 2 ) The design process of the model wind turbine required by the experiment is introduced . Based on the theory of blade - momentum theory , using the theory of Wilson ' s design , the blade of the model wind turbine is optimized by MATLAB programming tool . Finally , the production and manufacture are carried out , and the model wind turbine used in this test is determined .

( 3 ) In the wind tunnel , a model wind turbine wake flow field experiment observation research is carried out . Using the model wind turbine designed in ( 2 ) , a high - resolution and three - dimensional transient wake flow field information is captured by using a three - dimensional particle image velocity measurement technique under the condition of two sharp - speed ratio conditions , and the development and annihilation process of the full wind turbine blade tip vortex is revealed .

After the tip - tip vortex shedding from the tip of the blade , the helical movement of the tip vortex blocks the velocity recovery inside the wake region , and an axial velocity loss region is formed behind the wind turbine .

( 4 ) By using the experimental data , the comparison and verification of the widely applied wake - flow mathematical model is carried out on the current project . The results show that these models are different from the experimental data because of the different assumptions and simplification , and the accuracy of these models is to be improved .

( 5 ) Aiming at the deficiency of the existing tail current calculation model , the jet model of wind turbine wake flow is modified on the basis of experimental data . By analyzing the experimental results , the regional standard of the near and far end flow area of the wind turbine based on the " alternating jump " phenomenon of the tip vortex is put forward , and the calculation formula of the length of the near wake flow area is derived . The flow field characteristics of the near wake flow area of the wind turbine are combined with the jet theory , the wake jet model is corrected , and the accuracy of the wake flow calculation is improved .

Through the research in this paper , the physical mechanism of wake flow field in the horizontal axis wind turbine is revealed , the standard of wake partitioning is defined , the calculation precision of wake flow model is improved , and it is more suitable for the evaluation of wake effect of wind farm .
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM315

【参考文献】