Numerical simulation of flow in coolant pump for special nuclear reactor under positive and negative rotational speeds
YANG Congxin1,2, ZHANG Yang1,2*, QIAN Chen1,2
1. College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China; 2. Key Laboratory of Fluid Machinery and Systems of Gansu Province, Lanzhou, Gansu 730050, China
Abstract To identify the characteristics of reactor coolant pump(RCP)under positive and negative constant speeds, numerical simulations of the flow in the model coolant pump scaled down from the real pump with 0.5 scaling factor based on the pump affinity laws were carried out by using the SST k-ω turbulence model and structured-mesh. The flow rate was defined as “+” when the fluid flows into the pump from the inlet, otherwise, it was defined as “-”. The complete characteristic curves were predicted respectively with 16 operating points in the flow range of -0.8Qd - +2.0Qd under positive rotational speed, and 14 operating conditions in the flow range of -1.4Qd - +1.0Qd under negative rotational speed. The results show that at the same flow rate, the head and torque of the RCP under positive rotational speed are always higher than that under negative rotational speed. The impeller head and pump head have different variation trends. The impeller head curve is in upside-down “N” shape as the flow rate in the range of -0.1Qd - +0.4Qd under positive rotational speed, but it is in “V” shape when the flow rate is in the range of -0.4Qd - +0.1Qd under negative rotational speed. The internal flow results show that there is a secondary flow phenomenon in the impeller outlet. This flow pattern is mainly responsible for the drop in the impeller head under low flow rate conditions under positive rotational speed. The large-scale vortices in the impeller and the high-velocity region between the impeller and the radial diffuser are the main reason for the drop in the impeller head curve with negative rotational speed under low flow rate conditions.
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