Three-dimensional compressible turbulent flows and aerodynamic performance were numerically simulated for centrifugal tandem-blade impellers. The study was focused on the influence of relative circumferential arrangement configuration between the inducer and the exducer on the internal flows and aerodynamic performance of tandem-blade impellers. Five relative arrangement configurations were considered and the flows in tandem-blade impellers were compared with those in a conventional single row blade impeller. The numerical results indicate that

for the tandem-blade impeller

the relative circumferential arrangement configurations play important roles in the flow fields and aerodynamic performance. When the exducer is staggered with the inducer along the single rotation direction

the polytropic efficiency is lower than that of the single row blade impeller. When the factor of relative circumferential position lies from 0.0 to 0.4

the pressure ratio is higher than that of the single row blade impeller

and the highest pressure ratio increases by 1.4%. Moreorer

a relative smooth flow distribution along the circumferential direction forms at the impeller outlet

which may reduce the unsteady interaction between the impeller and the vaned diffuser and the aerodynamically generated noise sources there. When the exducer is staggered along the counter-rotation direction

both of the polytropic efficiency and the total pressure ratio of the tandem-blade impeller are lower than those of the single row blade impeller

and the outlet flow distributions vary quite along the circumferential direction.