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As the total pressure ratio of centrifugal compressors increases,the diffuser inlet flow becomes highly subsonic or even supersonic,which causes additional shock loss.The shock loss leads the stage performance to drop greatly.Pre-compression is an efficient method for reducing shock loss and improving the stage performance.To study the effect of wedge diffusers with pre-compression blades on centrifugal compressor performance,wedge diffusers with various pre-compression angles,divergence angles and numbers of blades were designed and investigated via a numerical method.As a result,it is found that the compressor stage achieves high peak efficiency when the pre-compression angle ranges from 2.5° to 5.5° and when the divergence angle ranges from 7° to 9°.As the number of blades increases,the total pressure ratio and adiabatic efficiency of the compressor stage increase slightly,whereas the surge margin of the stage decreases.