This study aims at improving the performance of a centrifugal pump by using different angular diffusers on the downstream side of the centrifugal pump impeller. Numerical and experimental studies have been carried out on different vaned and non-vaned diffuser with three different wall divergence angle (α) of 0°, 5° and 10° to achieve that purpose. The data analyses show good agreement between the numerical and experimental results. They reveal profound effect of the divergence angle (α) of angular vaned diffuser on the head and overall efficiency of centrifugal pumps especially at high flow rates as they broaden operating region of the centrifugal pump. In fact it is found that the head and overall efficiency of impeller with vaned diffuser α = 10° enhance by 15.4 and 9 percent respectively compared to that of centrifugal pump with no vaned diffuser at high flow rates. Furthermore the head and overall efficiency of impeller with vaned diffuser α = 10° increase by 5.7 and 7 percent respectively in comparison with the impeller with vaned diffuser α = 0°.
