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.