The effect of impeller velocity factor K

c

of a centrifugal compressor on the performance of centrifugal compressor stages was investigated by numerical simulation

and the effect of K

c

on the impeller inflow pattern was analyzed. The result shows that the decrease of K

c

can meliorate the flow field in the impeller when the value of r/b

1

is larger than 0.3; the gradient of static pressure along hub to shroud at the inlet of blade is decreased and the fluid meridional velocity becomes more uniform at the outlet of impeller

so the efficiency of the centrifugal compressor stage can be improved significantly

the maximum improvement of isentropic efficiency is beyond 1.5 percents. In addition

the analysis on the performance of compressor stages with di

fferent K

c

indicates that efficiency curve of the compressor stage moves to the right side and the pressure ratio curve moves to the upward with the decrease of K

c

and the operation range of the centrifugal compressor can also be extended.