Study on the influence of cavitation development on the performance of nuclear main pump

Abstract

In order to study the influence of cavitation on the external characteristics and inner flow field of nuclear main pump, based on the continuity equation, Reynolds N-S equation and RNG k-ε turbulence model, the whole flow field cavitation numerical simulation on nuclear main pump model under the design condition is carried out. The performance and internal flow field variation law of the nuclear main pump are obtained through the comparison and analysis when 4 kinds of cavitation conditions are chosen. The results show that the head, efficiency and power of the nuclear main pump have different sensitivities to the reduction of net positive suction head available (NPSHa). With the development of the cavitation process in the pump, the head declines most sharply and the power most moderately. Under the condition of cavitation, the bubbles generated by cavitation have a squeezing effect on the impeller passage, which makes the flow area decrease and the relative velocity of the fluid increase. Meanwhile, the value of maximum velocity appears near the outlet of the blade. Meanwhile, the bubbles generated by cavitation change the flow state of the cavitation region, which makes the kinetic viscosity of fluids, the turbulent dissipation rate and the loss of turbulent dissipation reduce.