Impacts of impeller blade number on centrifugal pump performance under critical cavitation conditions

Abstract

The number of impeller blades is a significant geometric parameter that considerably impacts centrifugal pump performance. A transient numerical analysis of a centrifugal pump is conducted to examine the influence of the variable impeller blade number on pump performance under critical cavitation conditions. Six different impellers with 3, 5, 7, 8, 9, and 11 blades are examined numerically at a rotational speed of 2900 r/min when other impeller parameters remain unchanged. Fields of interior flow and properties of centrifugal pumps are studied concerning static pressure, velocity magnitude, and vapor volume fraction using ANSYS Fluent to perform the numerical simulation. The results show that numerical analysis can accurately predict centrifugal pump internal flow. The current results match experimental and numerical data for the NPSH, with a 4.65% discrepancy. Blade numbers affect the flow field and pressure amplitude, especially at the outlet region. As blade numbers increase, pressure increases, and the impeller with 11-blade has the maximum pressure amplitude. The impeller with a seven-blade achieved its highest efficiency level, exhibiting a 0.48% improvement under non-cavitation conditions and a 1.4% improvement under critical cavitation conditions compared to the original model. Furthermore, the cavity size on an individual blade of a model with three-blade is more extensive compared to other models. In addition, the impeller with a nine-blade exhibits the lowest value of the vapor volume percentage. This research analyses the influence of different blade numbers on the performance of centrifugal pumps while operating under critical cavitation conditions. It aims to provide novel insights into the flow characteristics associated with such circumstances.