大弯角开槽叶栅槽道位置与结构研究

Slot Position and Structure of Large Camber Slotted Cascades

关键词:  大弯角叶栅  槽道处理  总压损失  附面层分离  角区分离

Key words:  Large camber cascade  Slot treatment  Total pressure loss  Boundary layer separation  Hub corner separation

摘要:

为拓宽大弯角扩压叶栅可用攻角范围，优化叶片吸力面流动分离结构，以一大弯角叶栅为研究对象，对叶片采用压力面到吸力面打通的双“C”型槽道结构处理，在保持槽道长度及其他参数不变的条件下，设置85%，80%，75%，70%轴向弦长四个出口位置研究槽道出口位置对叶栅性能的影响。研究发现，特定攻角下，槽道出口位于吸力面角区分离线起始点之后、尾缘分离线之前，对吸力面流动分离的控制效果较佳；在全攻角范围，槽道出口则取在0°攻角对应较佳出口位置为好。为减小槽道内总压损失，提出了一种“SC”型槽道改进结构，在80%轴向弦长槽道出口位置处与双“C”型槽道以及原型叶栅进行对比。结果表明，“SC”型槽道结构相比于双“C”型槽道结构，叶栅尾迹损失及槽道内总压损失减少，槽道出口射流速度提高，叶片尾缘处静压升高；相比于原型叶栅则能有效降低其在全攻角范围内的总压损失，基本消除叶片吸力面附面层分离，削弱角区分离，提高叶栅的扩压能力。

Abstract:

In order to widen the usable range of incidence angle of the large camber high-load cascade and optimize the flow separation structure of the suction surface of the blade， a large camber cascade was selected as the research object. The cascade blade was treated with a double ‘C’ slot structure， which was opened from the pressure surface to the suction surface. Keeping the length of the slot and other slot parameters unchanged and setting the four exit positions of 70%， 75%， 80% and 85% of axial chord length， the effects of the slot exit position on the performance of the cascade were studied. It is found that， under specific incidence angle， the optimal slot exit position， which controls well the flow separation on suction surface， is located after the suction surface starting point of hub corner separation line and before the trailing edge separation line. In the full range of incidence angles， the optimal slot exit position corresponds to the exit position at 0° incidence angle. In order to reduce the total pressure loss in slot， an improved structure of the ‘SC’ shaped slot was proposed， which was compared with double ‘C’ shaped slot and prototype cascade when the slot exit position is 80% axial chord length. The results show that compared with the double ‘C’ shaped slot structure ， the ‘SC’ shaped slot structure reduces the total pressure loss in the slot and cascade wake loss， increases the air jet velocity at the slot exit and the static pressure at the trailing edge of the blade. In addition， compared with the prototype cascade， ‘SC’ shaped slot structure can effectively reduce the total pressure loss in full range of incidence angles， and basically removes the boundary layer separation on the blade suction surface， weakens the hub corner separation， and improves the diffusing capacity of the cascade.