平面涡轮叶栅内旋涡结构的试验研究

Experimental Investigation on Vortex Structures in Linear Turbine Cascades

选择3种典型的平面涡轮叶栅,叶型折转角分别为68o、113o和160o,通过对其内部流场进行详细测量和流动分析,讨论叶型折转角对出口涡量分布、气流角分布以及流动损失的影响,并获得3种典型叶栅的旋涡模型。结果表明,在平面涡轮叶栅中存在着复杂的旋涡结构,而且对于不同的叶型折转角,旋涡模型也不同:随着叶型折转角的增加,流场中通道涡的强度不断增强,其位置也不断向叶片中部移动;受其影响,尾缘涡在整个流场中的地位则随着叶型折转角的增加而逐步降低。旋涡结构的变化会引起叶栅出口的气流角、密流和损失分布的明显差别,可以通过控制旋涡结构来重新组织流场。因此,认识叶栅内旋涡结构的基本特征可以为气动优化策略的选择提供依据。

A series of experimental measurements are performed in details on three typical linear turbine cascades with tuming angles of 68°, 113°and 160°. The effect of turning angle on outlet vorticity distribution, flow angle distribution and flow loss is discussed on the basis of detailed measurement and flow analysis of internal flow field. Then the vortex models of the three typical cascades are obtained. The experiment result shows that there exist complex vortex structures in linear turbine cascades. Moreover, for different turning angles, the vortex modes are also different. With the increase of turning angle, the intensity of passage vortex in flow field increases, and its position moves toward the middle of the blade, and affected by this, the position of trailing vortex in the whole flow field gradually lowers along with the increase of turning angle. The change of vortex structure will cause different distributions of flow angle and flow loss at the cascade outlet. The flow field can be re-organized by controlling the vortex structures. Therefore, understanding the basic characteristics of vortex structure in turbine cascade can provide the basis for the selection of aerodynamic optimization strategy.