Contactless in-process measurement of separated flow on non-scaled rotor blades of wind turbines

例如，流动分离的可视化对于更深入地理解风能转子叶片的真实的流动行为至关重要。与缩放测量对象的风洞实验相比，由于测量对象的尺寸（~100 m）以及相关的难以接近性和波动的过程中测量条件，在非缩放转子叶片上进行所需的非接触式现场测量特别具有挑战性。目前，流动分离测量是通过必须安装在转子叶片上或转子叶片中的标记物（例如羊毛簇或压力管）间接进行的。因此，这些测量方法安装起来很耗时，并且通常在空间分辨率和测量区域方面非常有限。它们也是侵入性的，因此会影响要测量的流动行为。因此，该项目的目的是验证和从根本上表征非侵入性热成像流动可视化，以识别和定位流动分离，基于一种新的时空评估，用于现场实际运行的风力涡轮机。该项目的重点是热成像图像的时空信号/图像评估的方法，以实现足够的对比度噪声比，尽管缺乏测量对象的主动加热，而无需修改转子叶片。将对流动引起的时间和空间温度波动进行评估，以实现流动分离可视化所需的灵敏度改进。在现场测量的特定挑战的背景下，测量链将被建模，主要的测量不确定性的组成部分确定和热成像测量方法的基本测量极限被确定。除了低信噪比之外，由于转子叶片的多轴运动，流动分离的可视化变得更加复杂。因此，计划二维图像到三维旋转转子叶片表面的几何分配。例如，基于基于模型的几何校准，将补偿局部变化的成像尺度。该测量方法将在规定条件下的风洞实验中进行验证，随后在静止和运行的非比例真实的风力涡轮机上进行验证和现场应用。

The visualization of flow separation is essential for a deeper understanding of the real flow behavior of wind energy rotor blades, for example. In contrast to wind tunnel experiments on scaled measurement objects, the required non-contact field measurements on the non-scaled rotor blade are particularly challenging due to the measurement object size (~100 m) and the associated difficult accessibility and the fluctuating in-process measurement conditions. Currently, flow separation measurements are carried out indirectly by means of markers such as wool tufts or pressure tubes which have to be mounted on or in the rotor blade. Therefore, these measurement methods are time-consuming to install and are usually very limited with respect to the spatial resolution and the measurement field. They are also invasive and thus influence the flow behavior to be measured.Therefore, the aim of the project is to validate and fundamentally characterize the non-invasive thermographic flow visualization for the identification and localization of flow separation based on a novel spatio-temporal evaluation for the use on real-scale operating wind turbines in the field. The focus of the project is the approach of a spatio-temporal signal/image evaluation of the thermographic images in order to achieve a sufficient contrast to noise ratio despite the lack of an active heating of the measurement object and without a modification of the rotor blade. The flow-induced temporal and spatial temperature fluctuations will be evaluated to achieve the required sensitivity improvement for the visualization of flow separations. In the context of the particular challenge of a field measurement, the measurement chain will be modelled, the dominant measurement uncertainty components identified and the fundamental measurement limits of the thermographic measurement approach are determined. In addition to a low signal-to-noise ratio, the visualization of flow separation is further complicated due to the multi-axis movement of the rotor blades. Therefore, a geometric assignment of the two-dimensional image to the three-dimensional, rotating rotor blade surface is planned. Based on a model-based geometric calibration, for example, the locally varying imaging scales will be compensated. The measurement method will be verified in wind tunnel experiments under defined conditions and subsequently validated and applied in the field on a non-scaled real wind turbine, at standstill as well as in operation.