## 5 Conclusions  
The experimental results validated the accuracy of the numerical simulation process of the multiphase transport pump. The pressure fluctuation and gas phase distribution in the compression unit and the impeller of this pump at a rated flow with diverse IGVFs were studied. The conclusions were as follows:  
1. For the same experimental and numerical simulation conditions, the pressurization capacity of the multiphase mixed-transport pump decreased gradually with increasing flow rate. The efficiency improvement of this pump was limited with increasing flow rates. Meanwhile, the relative discharge of the IGVF and the decrease of the pump head had a quantitative relationship under a rated-flow condition. The pressurization capacity of the mixed-transport pump decreased with increasing the IGVFs. At the equal flow rate condition, the pressurization capacity of the mixed pump decreased by more than 30% when the IGVF was greater than 13.5%.  
Figure 11: Water velocity distribution at diverse spans in the second impeller and diffuser under IGVF = 20%.  
Figure 12: Streamline distribution in the second-stage compression unit with different IGVFs.  
2. The amplitude of the pressure pulsation close to the impeller blade head suction surface increased gradually along the flow orientation. With increasing IGVFs, the pressure fluctuation intensity at the impeller and diffuser inlet increased significantly. This phenomenon was closely correlated with the gas accumulation and the low relative velocity area.
3. The main frequency amplitude increased continuously with increasing gas content. In most cases, the dominant frequency of the impeller was 583.3 Hz, which was affected by the diffuser vanes number, whose value is the product of the rotation frequency and the number of guide vanes. The same situation happened in the diffuser, where the dominant frequency value was 408.3 Hz and was seven times that of the rotation frequency. It was shown that the pressure pulsation dominant frequency was an integer multiple of the rotation frequency.
4. The gas in the impeller passage primarily gathered on the suction surface of the blade head close to the front cover plate. Due to the work of the centrifugal forces, the water was pushed to the back cover plate, increasing the GVF near the front cover plate. On the blade suction surface near the front cover plate, a low-velocity area caused by the flow separation was generated. Thus, the pressure pulsation of the impeller was further affected. Vortices in the diffuser were obvious, and the vortex position tended to move toward the inlet of the diffuser with increasing gas content.  
Investigation, numerical simulation, data analysis, and paper writing were carried out by [PERSON]; [PERSON] and [PERSON] conceived and supervised the study and edited the manuscript; and [PERSON] and [PERSON] wrote the manuscript. All authors reviewed the manuscript. All authors have read and agree to the published version of the manuscript.  
This study was supported by the National Key R&D Program of China (No. 2018 YFB1501900), the National Natural Science Foundation of China (NSFC, No. 51527808, No. 51679195 No. 51769012, and No. 51909212), the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2019 JQ-044), and the Scientific Research Plan Projects of Shaanxi Education Department (No. 19 JK0570).  
The authors declare no conflict of interest.