Studies on Vertical Axis Wind Turbines Technologies

垂直轴风力发电机技术研究

• 批准号: RGPIN-2014-04218
• 负责人: Nitzsche, Fred
• 金额: $ 1.75万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566376
• 关键词: Studies; Vertical; Axis; Wind; Turbines

The aeroelastic and aero-acoustic behaviour of Darrieus-type vertical axis wind turbines (VAWT) individually and in wind farm formations will be investigated. Darrieus wind turbines were common in the 1970's but they were phase out due to problems with excessive vibrations. Advances in "smart" control systems and blade pitch control to suppress vibrations and the advent of composite blade structures have revitalized this conceptual design nowadays. In addition, the necessity of building offshore wind farms in deeper water to minimize the unavoidable visual and noise pollution near populated areas have pushed the industry to consider floating wind turbines. Horizontal axis wind turbines are not appropriate to floating installations due to its inherent stability problems. In HAWT the centre of gravity of the turbine is pushed upwards due to the heavy electric generator. In floating installations, the centre of gravity needs to be close to the surface of the water to guarantee the floating stability of the turbine. VAWT are appropriate in this case because VAWT generators can be located at the base of the turbine. The "troposkien" (from the Greek "rotating rope") geometry has been usually invoked to design Darrieus VAWT. The "troposkien" is the shape that a chain takes when it is rotating at a certain rate. In this situation, the bending moment is absent and the tension is the only internal force present in the structure. Therefore, the "troposkien" shape minimizes the fatigue problems of the Darrieus geometry. The structural dynamic behavior of a curved beam shaped in the "troposkien" under the action of the unsteady aerodynamics will be investigated considering the non-linear effects due to both the structural curvature of the blade and the aerodynamic dynamic stall present in regions of the blade azimuth angle. The structural dynamics will be expressed in a state-vector mixed formulation form where both forces and displacements in the in- and out-plane directions will be considered as the dependent variables. The aerodynamic simulation of the VAWT will be developed incorporating a free-wake vortex model where each blade section will shed vortices due to the changes in the blade lift over time. The shed vortices (filaments or alternatively particles) will be let to evolve over space in a Lagrangian description of the flow by the velocity field induced by both the vorticity of the neighbouring vortices and the wind free speed. Tower (blunt-body) effects will be included for a better description of the flow. This numerical approach is computationally efficient to represent the free-wake in rotating wings as it is mash-less and so robust to unrealistic numerical dissipation of the vortex strength normally encountered in traditional (grid-based) computational fluid dynamics methods. Coupling the aforementioned models for the structure and the aerodynamics both the self-excited (flutter and limit cycle oscillations) and the aeroelastic forced response of the structure due to the unsteady dynamic and aerodynamic loading will be investigated numerically. Aero-acoustic emissions generated by the unsteady acoustic pressure on the blades will also be determined from the blade local lift to estimate the turbine noise footprint and compared with experimental data from wind tunnel tests with a scaled turbine instrumented with strain gauges. The final objective of the project will be to develop "smart" control systems to minimize the high vibration problems detected with earlier installations of the Darrieurs rotor and to enhance its performance (i.e. energy extraction) in wind farm installations where the free-wake of one turbine is affected by the presence of others.

将研究Darrieus型垂直轴风力涡轮机（VAWT）单独和风电场结构中的气动弹性和气动声学行为。Darrieus风力涡轮机在20世纪70年代很常见，但由于过度振动问题而被逐步淘汰。“智能”控制系统和叶片变桨控制的进步，以抑制振动和复合材料叶片结构的出现，使这种概念设计重新焕发了活力。此外，在更深的水域建造海上风电场以最大限度地减少人口密集地区附近不可避免的视觉和噪音污染的必要性促使该行业考虑浮动风力涡轮机。水平轴风力涡轮机由于其固有的稳定性问题而不适合浮式安装。在HAWT中，由于重型发电机，涡轮机的重心被向上推。在浮动安装中，重心需要接近水面以保证涡轮机的浮动稳定性。VAWT在这种情况下是合适的，因为VAWT发电机可以位于涡轮机的底部。“troposkien”（来自希腊语“旋转绳索”）几何形状通常被用来设计Darrieus VAWT。“troposkien”是链条以一定速率旋转时的形状。在这种情况下，弯矩不存在，张力是结构中存在的唯一内力。因此，“troposkien”形状最大限度地减少了Darrieus几何结构的疲劳问题。考虑到叶片结构曲率和叶片方位角区域的气动动态失速的非线性效应，研究了非定常气动力作用下“对流层”弯曲梁的结构动态特性。结构动力学将以状态向量混合公式的形式表示，其中平面内和平面外方向的力和位移都将被视为因变量。VAWT的空气动力学模拟将结合自由尾流涡流模型进行开发，其中每个叶片部分将由于叶片升力随时间的变化而产生涡流。脱落的涡（细丝或颗粒）将在空间中通过由相邻涡的涡度和风的自由速度引起的速度场在流动的拉格朗日描述中演变。为了更好地描述流动，将包括塔（钝体）效应。这种数值方法在计算上有效地表示旋转机翼中的自由尾流，因为它是无网格的，并且对传统（基于网格的）计算流体动力学方法中通常遇到的涡流强度的不切实际的数值耗散非常鲁棒。耦合上述模型的结构和空气动力学的自激（颤振和极限环振荡）和结构的气动弹性强迫响应，由于非定常动态和气动载荷将进行数值研究。还将根据叶片局部升力确定叶片上非定常声压产生的航空声发射，以估算涡轮机噪声足迹，并将其与装有应变计的缩尺涡轮机风洞试验的实验数据进行比较。该项目的最终目标是开发“智能”控制系统，以最大限度地减少Darrieurs转子早期安装时检测到的高振动问题，并提高其在风电场安装中的性能（即能量提取），其中一个涡轮机的自由尾流受到其他涡轮机的影响。