Abstract：In order to investigate the characteristics of pressure fluctuation in residual heat removal pumps, three-dimensional unsteady numerical simulations were conducted by the SST turbulence model in ANSYS CFX. The performance of the residual heat removal pump was obtained and compared with the experimental results. The pressure fluctuations at various monitoring points were measured and analyzed in time and frequency domains. The results indicate that the pressure fluctuations in impeller and diffuser change periodically. The period of the pressure fluctuation within impeller is 7. The pressure fluctuation is closely related with the blade number in diffuser, while the period within diffuser is 5 and the fluctuation is strongly linked with the blade number in impeller. The amplitudes of pressure fluctuation at inlet, middle area and outlet of the impeller are 0.018 23, 0.106 76, 0.177 51, respectively. The amplitudes at inlet, middle area and outlet of the diffuser are 0.095 56,0.076 02,0.012 44,respectively. The amplitudes within impeller increase gradually from the inlet to outlet but the transformation law within the diffuser is opposite. The main frequency of pressure fluctuation within impeller which is dominated by the rotation speed is 7fp. The fluctuation is increasingly affected by the diffuser from the inlet to outlet. The main frequency at the inlet of diffuser is 15fp, while the others are 5fp. The fluctuation frequency within the diffuser is determined by the blade passing frequency. The fluctuation is decreasingly affected by the impeller from the inlet to outlet of the diffuser. The main frequency within volute is 35fp, which means that the fluctuation within volute is determined by the blade passing frequency and related with the blade number of diffuser.
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