Impact of rotor-stator axial spacing on the gas-liquid-solid flow characteristics of a multiphase rotodynamic pump based on the Euler multi-fluid model

Multiphase rotodynamic pumps are used by the oil and gas industry to transport mixed media in pipelines. The characteristics of gas-liquid-solid flow in such pumps are significantly affected by the rotor-stator axial spacing so that further investigation is required. Based on the Euler multi-fluid model, the Computational Fluid Dynamics simulations were conducted in this study on the gas-liquid-solid multiphase rotodynamic pump at the rotor-stator axial spacings of 8, 10, 12, 14, and 16 mm, respectively. Changes in the pump's characteristics of external, multiphase flow, and pressure fluctuation were systematically analyzed by using ANSYS-CFX. The results showed that, an overall decreasing trend for the efficiency and head of the multiphase rotodynamic pump were demonstrated with increases in the rotor-stator axial spacing from 8 to 16 mm, which can be categorized into plummets I, moderation, and plummets II. As the rotor-stator axial spacing increased, the pressurization decreased from the inlet to outlet of guide vane while the aggregation of gas and solid increased. Additionally, vorticity increased and vortex structure was found to be more significant. As a result, the overall performance of the multiphase rotodynamic pump deteriorated. The pressure fluctuation in the multiphase rotodynamic pump was determined by the rotor-stator interaction and multiphase flow under gas-liquid-solid flow conditions, resulting in a non-positive correlation between the pressure fluctuation and the pump's external and internal flow characteristics. The location of maximum pressure fluctuation in the multiphase rotodynamic pump was changed from the impeller outlet to the guide vane inlet with increases in rotor-stator axial spacing.