Influence of Blade Wrap Angle on the Operational Stability of a Low-specific-speed Centrifugal Pump under Cavitation Conditions

We numerically investigated effects of flow field variations under cavitation conditions on the operational stability of a low-specific-speed centrifugal pump across five blade wrap angle configurations. The blade wrap angles considered were ۱۶۵°, ۱۷۰°, ۱۷۵°, ۱۸۰°, and ۱۸۵°. To ensure the reliability of the findings, the investigation was conducted using a combination of experimental measurements and numerical simulations. A visualized closed-loop experimental rig was constructed to perform cavitation experiments on the centrifugal pump, and uncertainty analysis was carried out. Sensitivity analyses were conducted to select the appropriate turbulence and cavitation models for the numerical simulations. The adopted numerical approach was validated through qualitative and quantitative comparisons with experimental results. The influence of blade wrap angle on stall vortices, shear strain rate, vapor volume and vapor volume fraction, cavitation compliance, and hydraulic performance were analyzed both qualitatively and quantitatively. Cavitation compliance was introduced as an indicator for assessing the centrifugal pump’s operational stability. For the condition that blade wrap angle was grown from ۱۶۵° to ۱۸۵°, distribution range and intensity of stall vortices, the regions and intensity of high shear strain rate, vapor volume and volume fraction, and the oscillation intensity of cavitation compliance all exhibited non-monotonic variations. These parameters reached their minimum values when blade wrap angle was ۱۷۵°. Similarly, the head and efficiency also exhibited non-monotonic variations and reached their maximum values when one blade wrap angle was ۱۷۵°. Therefore, centrifugal pump under the condition that one blade wrap angle was ۱۷۵° demonstrated the most stable operation under cavitation conditions. This study elucidated the action of blade wrap angle for development of flow instability under cavitating conditions, providing a theoretical basis for future research. The findings offer useful design guidance for centrifugal pumps aimed at suppressing cavitation-related instability and improving operational reliability.

کلیدواژه ها:

Blade wrap angle ، Stall vortex ، Shear strain rate ، Vapor volume ، Cavitation compliance ، Hydraulic performance