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摘要:
为探究从源头抑制角区分离的流动控制方法，采用数值模拟方法，以NACA65叶栅为研究对象，利用叶栅前缘端壁吸气技术控制马蹄涡，结合拓扑分析对叶栅通道内的三维流动结构进行精确重构，以研究前缘端壁吸气控制马蹄涡进而改善叶栅通道流场结构的机理。结果表明：叶栅前缘端壁吸气技术可以有效推迟马蹄涡形成并削弱其强度，同时在吸气狭缝末端形成一对反旋流向涡对，在向下游发展过程中与通道涡相互作用；前缘端壁吸气通过控制马蹄涡，降低端壁边界层厚度，叶栅前缘通道涡发展受限，由回流组成的叶表分离被抑制；前缘及压力面侧吸气(EPS)直接作用于马蹄涡压力面分支，通道涡强度进一步被削弱，角区分离模式由闭式分离转为不完全闭式分离。最后，对比最优吸气系数下不同方案出口总压损失，发现当吸气量为进口质量流量的0.2%时，EPS方案出口截面总压损失降低5.8%；并且通过调整吸气系数，可以获得较好的变工况控制性能。
Abstract:To explore the source flow control method for the corner separation, this paper takes the NACA65 cascade as the research object and applies the blade leading edge endwall suction technology to control the horseshoe vortex with the numerical simulation method. Combined with topology analysis, the three-dimensional flow field is accurately reconstructed and the control mechanism of the leading edge endwall suction is revealed to improve the cascade channel flow field performance. The results show that the leading edge endwall suction technology can effectively delay the formation of the horseshoe vortex and weaken its strength. Meanwhile, a pair of counter rotating vortices are formed at the end of the suction slit, which interacts with the passage vortex in the process of downstream development. By regulating horseshoe vortices, the suction lessens the thickness of the endwall boundary layer, inhibiting the formation of leading edge passage vortices and preventing surface separation caused by backflow. Because the leading edge and pressure side suction (EPS) directly acts on the pressure side leg of the horseshoe vortex, the passage vortex strength is further weakened, and the corner separation mode changes from closed separation to incomplete closed separation. Finally, the total pressure losses are compared at the outlet under the optimal suction coefficient. It is discovered that when the suction coefficient is 0.2%, the overall pressure loss at the EPS outflow section is decreased by 5.8%. At off-design situations, improved control performance can be attained by modifying the suction coefficient.
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Key words:
- compressor cascade /
- horseshoe vortex /
- corner separation /
- leading edge suction /
- topology analysis
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图 5 叶栅出口节距平均能量损失系数分布（z/C=146%）
Figure 5. Spanwise distributions of pitch-averaged energy loss coefficient at outlet pitch of blade cascade (z/C=146%)
图 6 各方案不同吸气系数下总压损失系数分布
Figure 6. Distribution of total pressure loss coefficients under different suction coefficient for each case
图 7 叶栅前缘涡系结构(Ω=0.52)
Figure 7. Vortex system structure at leading edge of blade cascade（Ω=0.52）
图 8 不同方案马蹄涡压力面分支涡系结构
Figure 8. Pressure side leg of horseshoe vortex system structure for different cases
图 9 不同方案马蹄涡吸力面分支涡系结构
Figure 9. Suction side leg of horseshoe vortex system structure for different cases
图 10 前缘吸气产生的流向涡结构
Figure 10. Streamwise vortices structure generated by leading edge suction
图 11 吸气控制对分离区拓扑结构的影响
Figure 11. Influence of suction control on topology of separated surface flow pattern
图 12 距离叶栅前缘10%弦长处边界层位移厚度及边界层动量厚度
Figure 12. Boundary layer displacement thickness and momentum thickness at 10% chord from leading edge of blade cascade
图 15 具有前缘及压力面侧吸气的叶栅通道涡系演化示意图
Figure 15. Schematic evolution of vortex flow pattern with suction at leading edge and pressure side
图 16 节距平均总压损失系数分布
Figure 16. Spanwise distributions of pitch-averaged pressure loss coefficient
图 17 不同冲角下总压损失系数分布
Figure 17. Distribution of total pressure loss coefficients under different incidence angle
表 1 不同吸气方案总压损失系数
Table 1. Total pressure loss coefficient in different suction scenarios
方案 $ \varpi /\% $ $ {C_{\text{s}}}/\% $ Ori 5.49 ES 5.70 0.0058 EPS 5.17 0.2070 ESS 5.75 0.0162 
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