Abstract: In order to clarify the effect of blade number matching between impeller and guide vane on the hydraulic performances of the reactor coolant pump (RCP), model pumps (at a scale =0.5) are studied. Many RCPs with different matching laws between the impeller blade number Z1 and the guide vane blade number Z2 are built based on the references and geometry parameters of the RCP. Then their performances are predicted by numerical simulation. After the performances are analyzed, results in the studies are as follows. When the impeller blade number increases with the other geometry parameters of the RCP constant, the heads of impeller and pump both tend to increase with increasing trend gradually slow. When the guide vane blade number increases with the other geometry parameters of the RCP constant, the best pump can make efficiency improve by 8.48% relative to the worst one. Vortices and hydraulic loss within the guide vane and circular casing are mainly concentrated in the hemisphere region which starts with the pump outlet and goes along the impeller rotation direction. The circular casing has more hydraulic loss than the other flow components in the RCP. And the hydraulic loss of circular casing at least accounts for 36.4% of the total hydraulic loss. What is more, at the designed condition, best blade number matching laws between impeller and guide vane are (Z1=4,Z2=9)、(Z1=5,Z2=12)、(Z1=6,Z2=11) and (Z1=3,Z2=7), namely the efficiency and head of the RCP get the best value on condition that the guide vane blade number is about double of the impeller blade number and the blade numbers are both relatively prime. In conclusion, the above results can provide reference for choosing blade numbers matching law between impeller and guide vane of the RCP.

Key words: blade number, guide vane, impeller, matching, reactor coolant pump