The results of a study for identifying optimum blade number of a transonic micro slope impeller with splitters were presented.An in-house-developed Navier-Stokes flow code was applied to the study.By increasing the blade

the blade load and separation on suction surface was decreased

and the internal flow was improved

but the low pressure zone was expanded in the entryway.In the event of excessive number of the blades

the full blade cannot work from the leading edge to the trail edge.Along with the augment of the blade number

the impeller performance curves move up and then down.As compared with the experience gained in the study of normal centrifugal compressor

the optimal blade number of the micro impeller is lesser.The lower Reynolds number

the effects of micro-scale and the biggish relative thickness of blade are contributing factors to produce the difference in optimal blade number.