## 3 Results and Discussions
### Effect of Blade Fillet  
The small geometry deviations which are likely to occur in real machines, such as blade fillet, sometimes is recommended in conventional stators to improve structural integrity. The size of the fillet is usually minimized because increasing the fillet radius will decrease aerodynamic performance due to increased profile drag. However, the addition of a fillet between the blade and the hub will reduce the interaction between the endwall and blade boundary layers. Therefore, it has not been determined if the fillet geometry will have a positive or negative influence on corner separation [13]. In this study, fillet radii (\(r_{filllet}/c=0\%\), 1.6%) are tested on the PVD cascade to determine the effect of the fillet on this specific blade. Moreover, the slot configuration on blades with a fillet is also investigated to determine the combined effect of these two methods. The effect of the fillet is shown in Figure 12. When a fillet is present, the total pressure loss coefficient decreases. For all of the cases, removing the fillet was found to increase loss, which is consistent with the results [PERSON] [12] found in his study. For the cascade with blade fillet and slot configuration, the performance of the slotted cascade with \(r_{fillet}/c=1.6\%\) is improved, compared with the original cascade with \(r_{filllet}/c=1.6\%\), while the total pressure loss coefficient is larger than the slot configuration without fillet. As the slot configuration is defined and analyzed from the original case, the slot geometry needs to be modified together with consideration of the blade fillet influence. In order to know the relationship between the blade fillet and the slot configuration, flow details in the passage are analyzed at the \(i=3^{\circ}\) incidence angle below. Figure 11: Influence of aspect ratio combined with the slot on limiting streamlines and the passage total pressure loss coefficient at the \(i=3^{\circ}\) incidence angle: (**a**) slot, \(h/c=1\); and (**b**) slot, \(h/c=1.65\). Figure 13 shows the limiting streamlines and the total pressure loss coefficient in the passage for different fillet radii at the \(i=3^{\circ}\) incidence angle. As the fillet would affect the interaction of the suction surface boundary layer with the overturned endwall flow, from the red streamline in Figure 13b, flow near the endwall has a tendency to move along the suction surface and shift to the midspan. The total pressure loss decreases slightly near the endwall, while increasing near the midspan, which is consistent with the results of [PERSON] et al. (2017). From Figure 13c, the slot configuration still has a positive effect on the corner separation and the large reverse region on the endwall has been eliminated. While 2D separation is generated about \(20\%h\) to the midspan and the profile loss on the suction surface has been increased. For the results on PVD cascade, comparing with the cascade without fillet, the slot configuration still has a positive effect on controlling the corner separation, while the effect of the slot configuration  
Figure 12: Influence of fillet radius for different incidence angles on the total pressure loss coefficient without the slot configuration. Figure 13: Influence of blade fillet on limiting streamlines and the passage total pressure loss coefficient at the \(i=3^{\circ}\) incidence angle: (**a**) origin, \(r_{fillet}/c=0\%\); (**b**) origin, \(r_{fillet}/c=1.6\%\); and (**c**) slot, \(r_{fillet}/c=1.6\%\). under the influence of the blade fillet is worse than the slot configuration without fillet. The reasons are as follows: one reason is that as the fillet can influence the interaction of the blade suction flow with the endwall overturned flow, the corner separation flow structure might be changed compared with the original case. Slot geometry needs to be modified or improved for the new flow pattern. The other reason is the combination effect of the slot configuration and the blade fillet leads to the increase of the total pressure loss coefficient near the midspan.