Visualization experimental study on the influence of inlet flow rate on internal flow in a multiphase pump

Abstract

Multiphase pumps serve as a kind of core equipment for oil and gas transportation in marginal oilfields. Their performance and operational stability are significantly influenced by the physical properties of the multiphase medium and the complex internal flow structures within the pumps. Through force analysis on bubbles, this study predicts their migration trajectories within the impeller passage. High-speed camera visualization experiments were performed to systematically examine the gas-liquid two-phase flow characteristics under various flow conditions. The results indicate that the flow rate considerably influences both bubble aggregation behavior and the structure of tip leakage flow. At the rated flow rate, bubbles migrate toward the trailing edge of the suction side under the influence of pressure gradients and accumulate. Under high flow conditions, bubble deflection is reduced, and overflow leakage dominated by high velocity is observed. At low flow rates, bubbles impinge on the pressure side and form gas pockets, while tip leakage is intensified with notable backflow. This study elucidates two distinct mechanisms driving tip leakage flow, namely pressure difference driven and velocity driven, and reveals that variations in inlet flow rate lead to flow separation and vortex evolution in the tip region.