Effects of the Centrifugal Pump Outlet Blade Angle on Its Internal Flow Field Characteristics under Cavitation Condition

Abstract

The outlet blade angle is a key geometrical parameter that governs how the impeller directly influences centrifugal pump performance. Therefore, a reasonable angle selection is crucial. To investigate the effects of the outlet blade angle on centrifugal pump internal flow field characteristics under cavitation conditions, this study employs a combination of a modified SST k-ω turbulent model with a Zwart-Gerber-Belamri cavitation model to perform transient flow simulations. Outlet blade angles of 15°, 20°, 25°, 30°, and 35° were tested. The results indicated that as the outlet blade angle increased, the relative liquid flow angle, vapor volume, and corresponding fraction first increased, then decreased, and finally increased again. Meanwhile, the distribution scope of each stall vortex on the suction surface became smaller, then larger, and smaller again, whereas the scopes of the pressure surfaces grew constantly as the outlet blade angle increased. Pressure fluctuations at all monitored points in the volute became weaker over time, and variations in the pressure fluctuations alternated with the outlet blade angle. The main frequency amplitude increased and the frequency doubling decreased as the outlet blade angle increased. Although the energy corresponding to the main frequency was unstable, it consistently held the dominant position. The duration that cavitation compliance was less than 0 first decreased and then increased as the outlet blade angle increased. For the impeller with an outlet blade angle of 25°, stall vortices accounted for the smallest regions, and the duration of negative cavitation compliance was minimized. In this case, the overall performance of the centrifugal pump was optimal.

Keywords

• centrifugal pump
• outlet blade angle
• cavitation
• net positive suction head available
• net positive suction head required
• computational fluid dynamics