Passive Flow Control on Wind Turbine Rotors using Self-Adaptive Camber

德国达姆施塔特工业大学流体力学和空气动力学研究所开发了一种载荷依赖的被动弧度控制概念，其特点是机械耦合的前后缘襟翼。波动的流入条件导致压力分布的改变，并在前缘襟翼上产生力矩。力矩以这样一种方式传递给后缘襟翼，即前缘襟翼的顺时针旋转导致后缘襟翼逆时针旋转。由此产生的变化翼型弧度是完全被动的，不需要传感器或控制单元。其特性完全取决于流固耦合作用和耦合机制的特性。引入该概念是为了减轻风力涡轮机转子叶片的负载波动，其总体目标是减少疲劳，提高转子耐久性和涡轮机寿命。在第一个资助期间，在风洞的二维流入条件下验证了该概念的功能。旋转系统中的流入条件与二维情况有根本的不同。科里奥利力和离心力引起气流径向重定向。与二维情况相比，横向流动引起了压力分布的差异。本文旨在研究在这些改进的流入条件下的自适应弧度概念：将在PP2研究涡轮上开发和测试具有自适应弧度机构的动叶。为了将横流的影响从虚拟力中分离出来，将进行额外的二维后掠翼实验。该方案的第二个目标是保证在不同于设计点的流量条件下的运行安全。这是通过在升力曲线的非线性状态下提出一个具有自适应弧度机制的二维模型来实现的。

A load-dependent passive camber control concept featuring a mechanically coupled leading and trailing edge flap has been developed at the Institute of Fluid Mechanics and Aerodynamics at TU Darmstadt. Fluctuating inflow conditions lead to modified pressure distribution and induce a moment on the leading edge flap. The moment is transferred to the trailing edge flap in such a way that the clockwise rotation of the leading edge flap results in a counter clockwise rotation of the trailing edge flap. The resulting change in airfoil camber is completely passive and does not require sensors or control units. Its characteristics are determined solely by the fluid-structure interaction and the characteristics of the coupling mechanism. The concept is introduced for alleviating load fluctuations on wind turbine rotor blades with the overall goal of reducing fatigue and increasing rotor durability and turbine lifetime. During the first funding period, the functionality of the concept was proven under two dimensional inflow conditions in a wind tunnel.Inflow conditions in a rotating system differ fundamentally from the two dimensional case. Coriolis and Centrifugal forces provoke a radial redirection of the flow. The cross flow causes a difference of the pressure distribution compared to the two dimensional case. This proposal aims at investigating the adaptive camber concept under these modified inflow conditions: Rotor blades with adaptive camber mechanism will be developed and tested at the research turbine of PP2. In order to isolate the influence of crossflow from the fictitious forces, additional two-dimensional experiments with a swept wing will be performed. A second objective of this proposal is to guarantee operational safety at flow conditions differing from the design point. This is done by submitting a two-dimensional model with adaptive camber mechanism to high angle of attack fluctuations in the non-linear regime of the lift curve.