With the exploitation of deep sea and desert oil fields, multiphase pumps have come into the public eye. However, due to the nature of the medium and operating environment, the performance of traditional multiphase pumps has diminished, leading to problems such as increased recovery cycles and rising costs. In order to obtain a high-head, high-reliability multiphase pump, this paper uses the model optimization method to design a complex pattern impeller. The best complex impeller with 17.25% increase in head was selected with the external characteristics as the optimization index, and a comparative analysis of the internal flow field was carried out between the complex impeller and original impeller when the inlet gas volume fraction was 10%. The results show that in the complex impeller, the short blade reduced the proportion of the high-speed zone, inhibited the appearance of the main blade suction surface low-speed zone, and significantly improved the return flow. The slope of the pressure boosting curve at the relative position 1.5–2.0 was increased, and the pressure boosting capacity was increased by 16.34 kPa. The short blade weakens the leakage movement while reducing the pressure effect on the main blade. In addition, the short blade not only improved the gas phase gathering but also reduced its size and made it closer to the main blade suction surface, which improved the uniformity of the gas phase distribution in the flow channel and also enhanced the inlet flow capacity. The results can provide a reference for future optimization and performance improvement of multiphase pump models.

In a multiphase pump, tip clearance is the required distance between the blade tip and the pump body wall of the impeller, forming tip leakage vortex (TLV), causing unstable flow and energy dissipation. In the present work, the enstrophy dissipation theory is innovatively applied to quantitatively study the energy dissipation of the TLV. The flow rate, tip clearance, and inlet gas void fraction (IGVF) play a crucial role in affecting the enstrophy dissipation of the TLV. The results show that increasing flow rate, tip clearance, and IGVF significantly exacerbate the TLV pattern and raise the TLV scale, which gradually raises volume enstrophy dissipation and decreases wall enstrophy dissipation. As the flow rate increases, the separation angle between the primary TLV trajectory and the blade gradually decreases, and widely dispersing the enstrophy dissipation near the shroud. However, as the tip clearance increases, the tip separated vortex scale increases and extends to the suction surface, raising the velocity gradient. Besides, as the IGVF increases, the secondary TLV develops from a continuous sheet vortex to a scattered strip vortex, increasing the significantly increasing the enstrophy dissipation. Considering the flow rate, tip clearance, and IGVF as independent variables, simple and multiple nonlinear regression models have the ability to predict the enstrophy dissipation of the TLV accurately.

In a multiphase pump, tip clearance is the required distance between the blade tip and the pump body wall of the impeller, and can regulate tip leakage vortex (TLV), causing unstable flow and energy dissipation. However, there are few studies on the energy dissipation caused by the TLV. In the present work, the enstrophy dissipation theory is innovatively applied to quantitatively study the energy dissipation of the TLV. The flow rate ( Q) , tip clearance ( Rtc) , and inlet gas void fraction ( IGVF ) play a crucial role in affecting the enstrophy dissipation of the TLV. The results suggest that increasing Q , Rtc , and IGVF significantly exacerbate the TLV pattern and raise the TLV scale, which gradually raises volume enstrophy dissipation and decreases wall enstrophy dissipation. The maximum pressure load in the impeller occurs at the 0.5 chord, where a strong TLV is generated, leading to significant enstrophy dissipation. As the flow rate increases, the separation angle between the primary TLV (PTLV) trajectory and the blade gradually decreases, and widely dispersing the enstrophy dissipation near the shroud. However, as the tip clearance increases, the tipseparated vortex (TSV) scale increases and extends to the suction surface, raising the velocity gradient. Besides, as the IGVF increases, the secondary TLV (STLV) develops from a continuous sheet vortex to a scattered strip vortex, increasing the pressure fluctuation intensity. Considering the flow rate, tip clearance, and IGVF as independent variables, simple and multiple nonlinear regression models for the enstrophy dissipation are established.