Study on Flow Field Excitation and Rotor Shaft Response of the High-Temperature Molten Salt Circulating Primary Pump

This study examines the impact of fluid excitation forces on the dynamic response of high-temperature molten salt circulating primary pump rotor systems. Unsteady simulations were conducted in ANSYS CFX to characterize pressure pulsation and radial forces across all impeller stages. Critical speeds and vibration modes were subsequently analyzed using SAMCEF to evaluate transient responses under varying flow rates. Key findings: Numerical performance predictions align with experimental data within a 5% error margin. The first-stage impeller exhibits a pressure-pulsation frequency of twice the rotational frequency (2 f_R), while the fifth-stage impeller oscillates at the guide-vane passing frequency (f_DPF). Under rated conditions, the radial force on the first stage is significantly larger than on the other stages. As the flow rate varies, the radial forces on the first and fifth stages change in opposite directions due to rotor–stator interaction. The rotor system’s critical speed (1894.5 r/min) exceeds the operating speed, eliminating resonance risk. Without radial forces, impeller displacements follow elliptical trajectories with maximum amplitude at the fifth stage. When radial forces are included, displacements become irregular, and shaft constraints cause peak displacement at the fourth stage. These findings provide useful insight for the design and analysis of molten salt primary pump rotor systems.