Study of the multi-size effect of bubbles in multiphase pump based on a coupled TFM-PBM model

The coalescence and breakup of bubbles lead to variations in bubble diameter during the flow within the impeller. This study examines the characteristics of bubble size distribution and internal flow mechanisms in multiphase pumps under diverse operating conditions, employing the Eulerian-Eulerian two-fluid model (TFM) and the population balance model (PBM) for analysis. The results show that the main factor leading to gas-liquid phase separation is the pressure gradient force due to the high-density difference. The bubble coalescence frequency at the impeller hub is higher than the bubble breakup frequency with increasing inlet gas volume fraction (IGVF). The large bubbles begin predominating and become the primary cause of air plugging the impeller channel. Moreover, the capacity of the rotating liquid within the impeller to carry the gas improves with an escalating flow rate, impeding the coalescence of bubbles. This dynamic positively influences the gas-plugging behaviour in the channel.