## 4 Results
### Flow between Ye Shan  
For studying the pressure coefficient distribution along the blade at different blade heights in the runner chamber and the flow velocity distribution in the impeller and guide vane areas, three annular sections with different blade heights were chosen from the hub to the rim in the runner and guide vane areas. The span values were 0.05, 0.2, and 0.95, representing near the hub, the mid-section of the blade, and near the rim, respectively, as shown in Figure 13.  
Figure 13: Section of the blade ring of the axial flow pump runner. Figures 14 and 15 are the distribution diagrams of the pressure coefficients at different blade heights under pump and turbine conditions, respectively. The horizontal axis \(Z\) represents the distance along the axis, and the vertical axis Cp represents the pressure pulsation coefficient. Considering that the four runner blades of the research object in this paper were exactly the same, only the data on one blade were selected for separate study when considering the pressure coefficient distribution at different blade heights. In the figure, except for small flow conditions, when operating near the design flow, the pressure coefficients at different blade heights were basically the same along the blade distribution trend. With the increase in the span value from the hub to the rim, the pressure coefficient also increased, and under the small flow rate condition, the distribution curve of the pressure coefficient Cp at different blade heights changed greatly, indicating that the change in flow had a larger influence on the flow field. When the flow rate was low, the flow state of the internal flow field was poor, the energy loss was serious, and there were even de-flow and backflow phenomena at the blade. Therefore, the pressure coefficient curve along the blade surface changed greatly. When operating under the turbine condition, as shown in Figure 15, under a different flow condition, the distribution trends of the pressure coefficient Cp curves at different blade heights were consistent. Under low flow conditions, the overall distribution of the pressure coefficient Cp near the rim was higher than that at the hub and the middle of the blade. As the flow rate increased, the value of the blade surface pressure coefficient Cp also decreased, indicating that under the design flow condition, the pressure variation on the entire blade was small, and the flow state was more stable at this time. We found that under the pump condition and turbine condition, the variation trend of the pressure coefficient distribution curve on the blade surface was basically the same, and the value of the pressure coefficient Cp decreased with the increase in the flow rate. Figure 14: _Cont._  
Figure 14: Pressure coefficient diagram under pump conditions. (i) 0.6Q. (ii) 0.8Q. (iii) 1.0Q. (iv) 1.2Q. We expanded the annular cross-sections divided according to different leaf height values to obtain the velocity streamline distribution diagrams, which are shown in Figures 16 and 17. Figure 16 is the velocity streamline distribution diagram under the pump condition, and Figure 13b is the velocity streamline distribution diagram under the turbine condition. From left to right are the velocity streamlines at the hub, the middle of the blade, and the rim, corresponding to span values of 0.05, 0.5, and 0.95, respectively. It can be seen from the figure that the velocity curves in the runner chamber are uniformly distributed on different annular sections, except for the small flow condition of forward running. Under the condition of small flow, it can be clearly seen that the streamline distribution on different annular sections was sparse and irregular, and there was a local backflow phenomenon at the inlet of the blade, indicating that the flow state was poor at this time.