Abstract: In order to study the effect of cavitation development on the external characteristics of a nuclear main pump and related internal flow region, this study, based on the continuous equation, the Reynolds time-average N-S equation and the RNG k-ε turbulence model, simulates cavitation behaviors occurred in full-flow region of a nuclear model pump under the design condition. Four cavitation conditions were selected in the study. By comparing simulation results with each other, the performance variation and the variation of internal flow region of the nuclear main pump were predicted when cavitation occurred. The simulation results show that when the nuclear main pump is cavitated, the external characteristics of the pump are sensitive differently to reduction of the effective airspace margin. As the degree of cavitation increases, the head decreases sharply and the power decreases more slowly. In cavitation state, the area of flow section is reduced and the relative velocity of fluid is increased due to the squeezing effect of air bubbles generated by cavitation on the flow path of impeller. In addition, because the bubbles generated by cavitation change the fluid state in the cavitation region and decrease the hydrodynamic viscosity, the turbulent dissipation rate and the turbulent dissipation loss in the cavitation region are reduced respectively.

Key words: reactor coolant pump, development of cavitation, the influence of performance, numerical simulation