Numerical Investigation of a Centrifugal Compressor with a Pre-Compression Wedge Diffuser under High Subsonic Conditions
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.