Research of Modal Analysis for Impeller of Reactor Coolant Pump

Abstract

This paper studies the influence of added mass, centrifugal force and hydraulic load on natural frequencies of a Reactor Coolant Pump (RCP) impeller. A series of comparative studies under different conditions were carried out on a modal test bench and a simulation platform. Modal analysis of a full-scale RCP impeller was conducted by simulation, and an improved design of impeller was proposed to prevent hydraulic resonance. These results indicated that hydraulic load increases natural frequencies of the impeller. While the centrifugal force slightly reduces them, but it is negligible. Because the distribution of hydraulic load has an effect to natural frequencies, a solution of cutting inlet edges of blades can be used to increase the natural frequency that may cause hydraulic resonance. In summary, our research shows that both added mass and hydraulic load have a significant influence on natural frequencies of the RCP impeller, and redistributing the hydraulic load can alter natural frequencies of the impeller.

Analysis of Stress–Strain Characteristics and Signal Coherence of Low-Specific-Speed Impeller Based on Fluid–Structure Interaction

“…Hence, obtaining a natural frequency of the pump and its mode shape via modal analysis can provide a reference for the design of the centrifugal pump. The linear differential equation of structural dynamics is the same as Equation (14). For the modal analysis, the overall load matrix of the structure is {F(t)} = 0, and the damping of the structure can be ignored; that is, [C] = 0.…”

“…During operation, if external excitation frequencies are close to or match these natural frequencies, it can easily lead to resonance and vibration, potentially causing structural damage and a decline in the performance of the centrifugal pump. Hence, it is particularly important to analyze the internal stress-strain characteristics and modal mechanical characteristics of low-specific-speed centrifugal pumps [14,15]. However, for the unsteady and complex flow in a pump, the pressure distribution on the impeller is uneven, which results in slight deformation.…”

Investigation on pressure pulsation and modal behavior of the impeller in a nuclear reactor coolant pump

“…17 Modal parameters play an important role in design optimization 18 and reliability analysis, 19 especially for the impeller with complex structures and high safety requirements. 20 Wang et al 21 conducted a modal analysis of a fullscale RCP impeller, and an improved design of the impeller was proposed to prevent hydraulic resonance. Due to the impeller submerged in a hostile fluid environment, modal properties are inevitably affected by the water, 22 and the EMA becomes more challenging.…”