基于CFD的二维垂直轴风力机性能计算

CFD BASED STUDY ON TWO-DIMENSION VERTICAL AXIS WIND TURBINES

采用计算流体力学方法(CFD)针对垂直轴风力发电机,开展简化的二维绕流特性研究。首先,基于开放型转子和增强型转子,研究网格节点数和壁面y+、计算时间步长和湍流模型等的变化对计算结果的影响,对计算模型和方法进行确认。随后,计算分析增强型垂直轴风力机与开放型垂直轴风力机的特性。结果表明,与开放性垂直轴风力发电机相比,增强型垂直轴风力发电机的功率系数和转矩系数有明显增加,且达到最大值的位置向叶尖速比增大的方向移动。然后对增强型垂直轴风力机发电机在不同来流风速下进行计算,发现增强型垂直轴风力发电机的转子转矩随来流风速增加,而转矩系数和功率系数与来流风速无关。最后,针对定子叶片在不同的方向开展计算研究。结果表明,定子叶片在不同方向时,增强型垂直轴风力机的转子转矩不同,且转矩到达峰值的位置也不同;在当前3个方向角中,叶片处于0°方向角时风力机具有最高的转矩系数,即具有最佳的功率系数。

In this paper,vertical axis wind turbines are investigated with Computation Fluid Dynamics method,with a simplified two-dimension model being applied to uncover flow characteristics around the turbines. Firstly,four factors,including node number and wall y+,time step and turbulent model,are taken into account to verify the CFD frameworks for present turbines with open rotor and augmented rotor respectively. Subsequently,the frameworks are applied to study the performance for the two kind of vertical axis wind turbines. It is found that power coefficient and torque coefficient of the augmented vertical axis wind turbine are significantly increased,compared with that of the open vertical axis wind turbine;and the point at which the coefficients reach the maximum value moves in a direction where the tip speed ratio increases.Then the augmented vertical axis wind turbine is studied at different wind speeds,and it is found that the rotor torque of the augmented vertical axis wind turbine increases with the wind speed,while the torque coefficient and power coefficient are independent of the incoming wind speed. Finally,stator blade orientations for augmented vertical axis wind turbine are investigated. It is found that the rotor torque of the augmented vertical axis wind turbine changes when the stator blades are at different pitch angle,and the position where the torque reaches the peak for three different pitch angle changes as well.Moreover,it is concluded that the torque coefficient of vertical axis wind turbines is highest,that is the wind turbine achieves the maximum power coefficient,when the stator blade is at a pitch angle of 0°.