不同掠弯扩压叶栅变工况气动性能比较

实验研究了变工况条件下由不同掠弯叶片组成的平面扩压叶栅出口总压损失及二次流矢量分布,并给出了叶片表面墨迹流动显示结果。研究表明弯掠叶栅能够最大程度地改善角区流动,避免流动分离,叶栅出口总压损失对冲角变化不敏感,正冲角下总损失增加较小且吸力面角区也不存在明显的分离。通过增大中径处的设计冲角或进行弯掠匹配优化进一步提高变工况性能的潜力巨大,对提高压气机性能具有实际价值。

An Aerodynamic Performance Study of Different Swept-Curved Compressor Cascades under Different Operating Conditions

Investigations in recent years showed that three-dimensional blade design using end bend,sweep and dihedral could reduce endwall loss,improve efficiency and stable operating range.STR (straight),SWF (forward swept),SCB (incorporating forward swept and positive curved) and SWB (backward swept) rectangular compressor cascades have been studied at design and off-design incidences to verify if SCB can achieve better aerodynamic performance.All types of swept or curved blades considered are symmetric to midspan,consisting of an circular arc section in the central part and swept or curved sections toward the endwalls.The effect of incidence change on the distribution of exit total pressure loss and secondary flow vectors of the compressor cascades has been experimentally investigated.Ink-trace flow visualization on blade surfaces was also conducted in a part of incidences.Compared with straight cascade,mechanisms of the total pressure loss increase and decrease with the change of incidence of various swept cascades at different spanwise positions were analyzed.The results show that compared to swept-forward cascades, the swept-curved cascade further prevents the low energy fluid accumulation, which may induce separation in the endwall/suction surface corner region;therefore,remarkably reduce total pressure loss in that region.Even at larger positive incidence the total loss of the swept-curved cascade increases smoothly and no flow separation was observed in the corner.In general,the total pressure loss of swept-curved cascade is not sensitive to incidence change.The study supports the conclusion that SWF and SCB conduce to the improvement of stall margin near the endwall even at higher incidence.Moreover,it is supposed that better aerodynamic performance of SCB can be achieved by increasing design incidence at midspan and by optimizing the matching of swept blade angle and height,and curved blade angle and height.