Research on the mechanism of multiphase pump pressurization failure process under stratified boundary conditions

The helical-axial multiphase pump, as a crucial power device in oil and gas extraction and transportation, has been extensively and profoundly researched. However, the effects of unconventional boundary behaviors on pump performance and internal flow mechanisms remain insufficiently understood, creating significant obstacles to the optimization design of the helical-axial multiphase pump. This study first confirms the existence of stratified inflow through visualization experiments, and then employs numerical simulations with stratified flow as the boundary condition for analyzing the helical-axial multiphase pump. The results indicate that stratified inflow has a markedly adverse impact on both pump head and efficiency; notably, at a gas volume fraction of 30%, the pump head decreases from 7.29 m to 1.67 m. The underlying mechanisms can be elucidated through changes in pressure distribution and velocity along the impeller streamlines. Stratified inflow causes the pressure curve to transition from a parabolic shape to an approximately linear configuration, leading to the presence of a cis-pressure gradient at the leading edge of the impeller, which results in unnecessary energy losses. Based on the impeller channel velocity distribution, it captures the presence of undesirable channel phenomena such as fluid roll-up and reflow in the low velocity region of the impeller. This research provides a detailed discussion of the overall impact of stratified inflow boundary behavior on pump performance, and the findings offer essential data for understanding failure mechanisms and optimizing the design of helical-axial multiphase pumps.