The three dimensional blade shape of Eckardt’s backswept impeller was modified, expecting better aerodynamic performance of the internal flow field. Blade angle distributions and parts of the meridional contours were changed, while impeller diameter, blade number, blade thickness and blade inlet and exit angles remained unchanged. The casing contour in the vaneless diffuser is additionally changed in a smooth manner to obtain 15% pinched flow channel at the exit. With the help of the three dimensional compressible Navier-Stokes analysis method, some improvements in the aerodynamic characteristics of the internal flow field were found; a more uniform flow field in the circumferential direction at impeller discharge was established, and a more favorable rise of static pressure near the casing in the impeller passage was made. A more effective increase of static pressure in the vaneless diffuser was also found. But a less uniform flow field in the spanwise direction at impeller exit resulted. The same levels of total-to-total pressure ratio and isentropic efficiency of the compressor were obtained, while an increase of choking flow rate was obtained due to increased throat area.

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