Proper orthogonal decomposition energy analysis in a nuclear reactor coolant pump based on PIV at the best efficiency point

Abstract

The nuclear reactor coolant pump (RCP) is the core equipment of a nuclear power plant (NPP), and its stable and efficient operation is one of the keys to the development of the RCP. The RCP's large-scale and high energy flow structure can be revealed through effective experimental and post-processing methods, which will help fully understand the flow mechanism. Thus, the present work aims to conduct a comprehensive study on the RCP model pump based on Particle Image Velocimetry (PIV) flow field measurement, internal flow structure analysis, and POD (Proper Orthogonal Decomposition) at the best efficiency point. From the POD overall energy analysis, it is found that even if the diffuser is installed in the spherical casing, the energy distribution of each diffuser flow channel has great difference. Through the analysis and comparison of the original flow and the flow field after POD, the main flow structure in the diffuser flow channel 2 is the wake flow vortex shedding γ area. Still, the primary energy area is the low-speed area close to the discharge nozzle after POD. Hence, the main flow structure in the diffuser flow channel is inconsistent with the primary energy area, which proves that it is not comprehensive to analyze the flow loss only from the perspective of flow field analysis. POD has apparent advantages in decomposing flow coherent structures of different scales with different energies. The high energy flow structure can be more clearly clarified through the mode decomposition of POD.