Effect of non-uniform inflow on vortex structure of a small modular reactor coolant pump

•The paper focus on the effects of non-uniform inflow on a small modular reactor coolant pump (SMRCP).•This paper delves into the vortex structure inside the SMRCP to evaluate the impact of non-uniform inflow on its performance.•Using the Q-criterion to identify complex vortex structures and analyzing the mechanism of non-uniform inflow.•The internal flow state of key hydraulic components of the SMRCP during one rotation cycle is analyzed. In small modular reactors, the extremely short distance between the steam generator (SG) and the reactor coolant pump (RCP) results in a non-uniform inflow at the pump inlet. Therefore, in order to investigate the effect of non-uniform inflow on the small modular reactors coolant pump (SMRCP), the internal vortex structure of the SMRCP was investigated in this study. Firstly, the uniform and non-uniform inflow models were constructed for the comparison of the study, and the CFD method was used to obtain the hydraulic characteristic curve and internal flow field information of the pump, and the CFD results were verified by experiments. The results show that the efficiency and head of the uniform inflow model is both higher than that of the non-uniform inflow model, and the non-uniform inflow has an effect on the performance of the pump. Secondly, by analyzing the velocity streamline distribution and vortex distribution under the pump steady calculation results, it is found that the non-uniform inflow will greatly change the flow state in the pump, and a large-scale reflux vortex is formed at the outlet of the casing under the non-uniform inflow, and the vortex structure changes the flow distribution in the casing. Finally, the vortex distribution of the impeller channel under transient calculation of the pump under different models for one week of impeller rotation, the turbulent kinetic energy distribution of the diffuser inlet and outlet and three-dimensional vortex distribution are extracted for comparison, and the analysis shows that the vortex structure of the SMRCP is slow to dissipate due to the influence of the non-uniform inflow, and the turbulence kinetic energy dissipation is serious, which influences the performance of the pump. This study provides new directions for optimizing the performance of the SMRCP under non-uniform inflow.