Effect of the starting position of the C-type trailing-edge blade on the performance of the helical axial-flow gas–liquid multiphase pump

The helical axial multiphase pump exhibits significant advantages in petroleum extraction. However, under gas–liquid two-phase conditions, severe gas accumulation often occurs near the impeller trailing edge, which adversely affects operational stability and overall performance. To date, this trailing-edge gas stagnation issue remains unresolved. Inspired by flow control strategies of trailing-edge flaps in aerospace and wind energy applications, this study proposes an innovative C-shaped trailing-edge modification. Impeller models with varying starting positions were established, and numerical simulations were carried out using Fluent, coupled with the Euler multiphase model and the shear stress transport (SST) k–ω turbulence model, to systematically evaluate the effects of the modified design on pump performance, internal flow structures, and phase distribution. The results reveal that the C-shaped trailing edge effectively restructures the internal pressure field, reduces the pressure difference between the suction and pressure sides at the trailing edge, suppresses gas accumulation and backflow, optimizes velocity distribution and pressure gradient, and significantly lowers local entropy production, thereby improving energy utilization efficiency. Among the tested designs, the starting position of α = 0.8 demonstrated the best performance at inlet gas volume fractions (IGVF) of 20%–50%, achieving an efficiency increase in 3.08%–4.40% and a reduction in entropy production of up to 86%. This study provides robust theoretical and engineering insights for enhancing performance and optimizing structural design of multiphase pumps under complex operating conditions.