## 3 Results and Discussions  
### Effect of Pitch-Chord Ratio  
Improvement of the pitch-chord ratio would cause an improvement of the loading and diffusion factor of the blade, which would also have a great impact on the corner separation in the passage. A large spread of the separated region with a significant extent of reverse flow was observed by [PERSON] [33] when the pitch-chord ratio increased from \(s/c=0.6\) to \(s/c=1.25\) (reduction in solidity). Based on the previous work of [PERSON] et al. [25], the slot at the root of the blade has a significant effect to control the corner separation.  
In order to understand the part played by the pitch-chord ratio with effects of the slot configuration at the root of blade, the datum chord length is maintained and the pitch-chord ratio is varied from the datum \(s/c=0.926\) to \(s/c=1\) with and without the effect of the slot configuration.  
Figure 5 shows the influence of the pitch-chord ratio on the overall performance of the cascade from \(-7^{\circ}\) to \(7^{\circ}\) incidence angles. The total pressure loss increases 33% in \(s/c\) from 0.926 to 1 at \(0^{\circ}\) incidence angle for the original cases. The slotted cascade significantly improved the overall performance, especially for the slotted cascade with \(s/c=1\). Although the original cascade stalls at a \(0^{\circ}\) incidence angle by the increase of the pitch-chord ratio, the performance of the slotted cascade is basically the same as the slotted cascade with \(s/c=0.926\) and the total pressure loss is significantly reduced compared with the original ones. Similar changes are also observed in Figure 4b for the turning angle.  
Figure 6 shows the variation of the total pressure loss coefficient for the EXP test plane at \(i=0^{\circ}\) and \(3^{\circ}\) incidence angles. It is evident that the total pressure loss increases with increasing pitch-chord ratio  
Figure 4: Volume streamlines in the flow passage: (**a**) original cascade; and (**b**) slotted cascade.  
for the original cases. This illustrates that more of the flow tends to be separated when the number of blades is decreased. The average total pressure loss reduces significantly in the corner region from the endwall to 30% spanwise by the slot configuration. The results correspond well to the above incidence characteristics. Furthermore, it can be predicted that the reduction of the flow blockages would be beneficial for improving the inlet working conditions of the downstream blade rows.  
The surface flow pattern shown in Figure 7 indicates the influence of the pitch-chord ratio and slot configuration on the formation of the topological structure on the suction surface and the endwall. From [PERSON]'s theory [34], three-dimensional separation develops from corner separation at \(s/c=0.926\) to hub-corner stall at \(s/c=1\) for the original cascade at a \(0^{\circ}\) incidence angle. The corresponding total pressure loss increases for the hub-corner stall case. While, for the slotted cascade at a larger pitch-chord ratio, the injection flow from the slot alters the nature of the hub-corner stall vortex. The most noticeable phenomenon is the remarkable reduction of the hub-corner stall in both its strength and size. The total pressure loss at the blade trailing edge is significantly weakened due to the changed endwall flowfield. Overall, the cascade performance has been significantly improved, which can be seen from Figure 4.  
Figure 5: Influence of pitch-chord ratio for different incidence angles on: (**a**) total pressure loss coefficient; and (**b**) flow turning angle.  
Figure 6: Influence of pitch-chord ratio on the spanwise profile of the total pressure loss coefficient: (**a**) \(i=0^{\circ}\); and (**b**) \(i=3^{\circ}\).