从纵横向流场分析垂直轴风力机功率随转速的变化

为了进一步明晰风轮转速对垂直轴风力机功率输出的影响,以某垂直轴风力机为研究对象,基于Fluent计算软件,采用SST k-ω湍流模型结合滑移网格技术,利用SIMPLE算法迭代,采用二阶迎风格式对垂直轴风力机进行非稳态计算.计算得到了不同转速下的风轮输出功率,通过将计算结果与试验结果进行对比分析,进一步验证了风轮功率随转速变化的规律.风轮速度场研究给出了尾迹不同位置处的纵向剖面速度云图,其中尾迹纵向剖面速度云图中的低速区出现了竖直方向对称而横向不对称现象.同时,通过对比风轮在不同转速下的尾迹流场纵向剖面速度云图和横向涡量场云图的差异发现风轮在额定转速下吸收风能最多,涡量损耗最小,并分析这种现象的诱因,从纵向流场和横向流场双重角度解析了风轮在额定转速下输出功率最大的原因,更加清晰地揭示了风轮输出功率随转速变化规律的机理.研究内容通过纵向截面和横向截面双重角度展现了风轮流场的变化,可为垂直轴风力机的设计和气动性能改善提供参考.

Analysis of vertical axis wind turbine power changing with rotating speed from vertical and horizontal flow fields

To further clarify the effect of the rotor′s rotating speed on the vertical axis wind turbine′s power output, taking a small vertical shaft wind turbine as the study object, based on the Fluent calculation software, using the SST k-ω turbulence model combining with sliding grid technology, and using the SIMPLE algorithm iteration and the second-order windward format, we calculated the vertical axis wind turbine in the unsteady state and obtained the wind turbine′s power output at different rotating speeds. Comparing the calculated with the experimental result, we confirmed the law of wind turbine′s power changing with a rotating speed. Wind turbine′s velocity field study gives the wake velocity contours of the longitudinal profile at different locations, and the low-speed section in the wake longitudinal profile velocity contours presents a vertical symmetry and horizontal asymmetry phenomenon. At the same time, by comparing the wind turbine′s wake flow field longitudinal profile velocity contours and the horizontal vorticity field contours at different rotating speeds, it is found that wind turbine has the maximum absorption wind energy and the minimum vorticity loss at a rated speed. And the cause of this phenomenon is analyzed. From the longitudinal flow field and the transverse flow field, we analyze the reason for wind turbine′s biggest power output at the rated speed,more clearly revealing the mecha-nism of wind turbine′s output power changing with the rotating speed. Research, from a dual angle of the longitudinal cross-section and the horizontal cross-section, shows the change of wind turbine′s flow field, which can provide the reference for the design of the vertical axis wind turbines and the aerodynamic performance improvement.