Evolution mechanism of internal flow in the hump region and hump optimization of axial-flow reactor coolant pump

The Nuclear Reactor Coolant Pump (RCP) serves as a pivotal equipment in nuclear power plants, and its operational reliability is directly linked to the overall safety of the plant. When operating in the hump region, axialflow reactor coolant pumps inevitably experience significant vibration and noise. Therefore, it is necessary to study the internal flow characteristics in the hump region to achieve effective control and increase the hump margin, keeping it away from the normal operating region. This study conducted analyses of pressure pulsation characteristics under various flow rates through experimentation. Additionally, numerical simulations were employed to scrutinize the internal flow of the pump under corresponding flow rates. Research has found that the disturbance of intermediate frequency signals is the main reason for the increase in pressure fluctuations in the hump region, rooted in the annular flow at the impeller inlet and vortex phenomena in the flow channel. Subsequently, the performance of the hump region was improved by optimizing the design of the vane inlet attack angle. The conclusions drawn from this study provide insights and a foundation for the optimal design of reactor coolant pumps.