Performance increase and improvement of the fatigue strength of vertical axis water turbines through active blade adjustment

Darrieus涡轮机是升力驱动的垂直轴横流风力和水力涡轮机（VAWT）。涡轮机的最佳操作范围是在2和5之间的叶尖速度比（切向叶片与流速之间的比率）。它们可以成为风能、河流能、海洋能或潮汐能等可再生能源发电的有趣解决方案。与基于水平轴的系统相比，它们还在区域开发方面提供了显著更高的效率。它们的功能与流动方向无关;它们可以很容易地被设想为模块化系统，这在经济上是有前途的。然而，涡轮机中的流动是非常复杂的。到目前为止，还没有令人满意的分析模型，其空气动力学行为，这将允许一个简单的设计水平轴涡轮（HAWT）。入射角、相对速度以及因此湍流特性随着转子的旋转角而改变。这导致在每次旋转的显著部分期间的动态失速。通过主动俯仰迎角，由于抑制了深度失速，可以显著提高效率以及自起动能力。与水平轴风力发电机不同，桨距函数不仅取决于叶尖速比，还取决于旋转角度，这就要求控制系统具有高度动态性，控制响应时间取决于转速。在一个跨学科的项目中，涉及流体力学和电气驱动系统领域，将在两年内实现以下目标，实施三个实验重点工作包：1。提高涡轮机的效率2.通过最小化负载变化提高抗疲劳性3.更好地了解垂直轴风力机的流体力学，特别是动态失速。基于实验的优化算法设计，以估计主动变桨控制的优化轨迹5.开发了一种新型的有限角力矩电机，其具有薄而长的格式，允许将桨距致动器集成在转子叶片中。分散安装的致动器应允许更高的自由度，以提高涡轮机效率。力矩马达之高动态轨迹控制器之设计。

Darrieus turbines are lift driven vertical axis cross flow wind and water turbines (VAWT). The turbine’s best operation range is in a tip-speed-ratio between 2 and 5 (ratio between the tangential blade to flow speed). They can become an interesting solution for electrical power generation from renewable energy sources like wind, river, ocean or tidal energy. They also offer a significant higher efficiency in the area exploitation, compared to horizontal axis based systems. Their functionality is independent of the flow direction; they can easily be conceived as a modular system, which is economically promising. However, the flow in the turbine is very complex. Until now there exists no satisfying analytical model for its aerodynamical behavior, which would allow a simple design comparable to horizontal axis turbines (HAWT). The angle of incidence, the relative speed, and thus the turbulence properties change with the rotation angle of the rotor. This leads to dynamic stall during a noticeable part of each revolution. By actively pitching the angle of attack, the efficiency can be significantly raised, as well as the self-starting capability, due to the inhibition of deep stalling. In contrast to HAWT, the pitch function is not only depending on the tip-speed-ratio, but also on the rotation angle.This requires a highly dynamical control system, with control response times depending of the revolution speed. In an interdisciplinary project, involving the fields of fluid mechanics and electrical drive systems, the following objectives will be achieved in two years, implementing three work packages with experimental focus:1. Improving the turbine’s efficiency2. Improving the fatigue resistance by minimizing the load variations3. Getting a better knowledge of the fluid mechanics in VAWT, in particular concerning dynamic stall.4. Experimental-based design of an optimization algorithm to estimate the optimized trajectory for the active pitch control5. Development of a new class of Limited-Angle Torque Motor with a thin and long format allowing the integration of the pitch actuators in the rotor blades. The decentralized mounted actuators should allow a higher degree of freedom for the improvement of the turbine efficiency.6. Design of a high dynamic trajectory control with minimal energy cost for the torque motors.