Abstract:  In order to adapt to the harsh application environment of distributed wind turbines，while meeting the needs of power regulation and fan self-protection，a new type of umbrella wind turbine was proposed. In order to study the influences of the umbrella wind turbine wheel contraction angles on the wake characteristics and output characteristics，the numerical simulation and wind tunnel tests were carried out respectively. The results show that when the contraction angles of the wind turbine wheels increase，the swept areas decrease，the wake diameters decrease，the axial influence ranges of the wakes increase，and the speed recovery slows down. At the same time，the strengths of the tip vortex may decrease. The strengths of the central vortex first increase and then decrease. However，the strengths of the central vortex are always greater than those of the tip vortex，so the speed losses behind the blade roots are always greater than those of behind the tips. Besides，the wind tunnel tests also verify the effectiveness of the wind wheel contraction angles on power control. 

Key words: umbrella wind turbine, wake, vorticity, output characteristic

摘要： 为适应分布式风力发电机的恶劣应用环境，同时满足功率调控以及风机自我保护的需求，提出了一种新型伞形风力机。为研究伞形风力机风轮收缩角对尾流特性和输出特性的影响，分别进行了数值模拟和风洞试验。研究结果表明：伞形风力机风轮收缩角增大后，扫掠面积减小，尾流直径减小，尾流轴向影响范围增大，速度恢复减缓，同时会导致叶尖涡强度减小，中心涡强度先增大后减小，但是中心涡强度一直大于叶尖涡强度，所以叶根后的速度亏损要一直大于叶尖后的速度亏损。此外，风洞试验也验证了风轮收缩角对功率控制的有效性。

关键词: 伞形风力机, 尾流, 涡量, 输出特性