## 5 Conclusions  
In this paper, the pressure pulsation at the inlet of the front guide vane and the outer edge of the inlet of the runner was measured by means of a real machine test when the axial flow pump was running under the design conditions. The pressure pulsations on the interface and the flow state of the runner chamber were compared, and the test results were used to verify the feasibility of the numerical simulation. At the same time, the external characteristic curve of the unit was also measured to verify the stability of its operation. In the future, if scientific research conditions allow, the model can be used to test the pressure pulsation value under reverse operation and the internal flow state of the pump unit under two-way operation, so as to better verify the reliability of the numerical simulation. The conclusions are as follows:  
1. The external characteristic curve of the pump unit measured by the test was compared with the characteristic curve of the pump unit obtained by numerical simulation.  
Figure 17: Velocity streamline distribution under turbine condition. (**i**) span = 0.05. (**ii**) span = 0.5. (**iii**) span = 0.95.  
Although there was a certain deviation at low flow, the error was within 3%, and the test value of the external characteristic curve and the simulated value were basically consistent, proving that the numerical simulation results using this model are credible. When running under the design flow conditions of the real machine test, the pressure pulsation at the inlet of the front guide vane and the inlet of the runner was measured, and the comparison with the numerical simulation monitoring value was also very consistent. The accuracy of the numerical simulation was fully demonstrated.
2. When the pump was running under the working condition, the amplitude of the pressure pulsation coefficient decreased with the increase in the flow rate. Under the same flow conditions, along the flow direction, the pressure pulsation coefficient had the largest amplitude and the largest change range at the inlet of the runner. There were four peaks and troughs in a single cycle, indicating that the change in the pressure pulsation was obviously affected by the dynamic and static interference. The periodic change law was closely related to the number of blades. When the flow rate was low, different degrees of the sub-frequency spectrum appeared in the low frequency band, indicating that the flow state was poor; when operating under the turbine condition, with the flow rate increasing, the amplitude of the pressure coefficient also decreased.
3. Under the pump condition and the turbine condition, the distribution trend of the pressure coefficient was consistent under different flow rates. With the flow rate increasing, the amplitude decreased constantly, indicating that when the blade operated near the design flow rate, the change in the blade surface pressure was small, and the flow was more stable.  
Conceptualization, D.W.; methodology, D.W.; formal analysis, D.W.; investigation, D.W.; resources, D.W.; data curation, D.W.; writing--original draft preparation, D.W.; writing--review and editing, Y.B.; visualization, D.W.; project administration, Y.B. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the National Natural Science Foundation of China (11402115) and the Jiangsu Province Natural Science Foundation of China (BK20130782).  
Not applicable.  
The authors declare no conflict of interest.