Numerical investigation of residual heat removal pumps based on fluid-structure interaction in 1000 MW nuclear power plants

Residual heat removal pump (RHRP) is one of key equipments in 1000 MW nuclear power plants; its faction is to transport high temperature and pressure medium. Vibration and dynamic stress which is caused by the interaction between the fluid and structure can affect the reliability of RHRP. This paper presents an investigation of internal flow field of residual heat removal pumps, by using a combined calculation for turbulent flow and structure response of impeller was first established using one-way coupling method. For the calculation, the flow field is based on Reynolds-averaged equations that resemble the shear stress transport (SST) k-ω turbulence model and the structure response is based on elastic structural dynamic equation. The dynamic stresses in the rotor system are computed according to the fourth strength theory. The results show that the domain frequencies of pressure fluctuations of monitors on the outlet of impeller are 5 f_n (rotating shaft frequency), 10 f_n, 15 f_n and 20 f_n. The amplitude of the relatively large pressure fluctuations peak is lowest under the design flow rate operating condition. The time-average radial force value at the design condition is the smallest. The hydraulic force magnitude at the maximum operating condition is the largest and phase different can be clearly seen among the results obtained under different conditions. The relatively large stress of rotor for all conditions is the biggest at shaft shoulder near the bearing, and it increases with flow rate. The relatively large displacement value of monitoring point at the impeller outlet is bigger than monitoring point at the wear ring of impeller.