Effects of pre-whirl and blade profile on the hydraulic and cavitation performance of a centrifugal pump

Abstract

The effects of pre-whirl and modified blade profile on the hydraulic performance and cavitation flow of the centrifugal pump are investigated quantitatively with the numerical simulations. The results show that the hydraulic efficiency of the off-design flow rate can be improved with the positive pre-whirl angle owing to significantly reduced friction loss, whilst the negative and positive pre-whirl can give rise to the higher and lower head coefficient respectively compared with that of no pre-whirl condition. Besides, the pre-whirl design is confirmed to have the ability to improve the cavitation performance of centrifugal pump, while the positive and negative pre-whirl are more suitable for the larger/design and smaller flow rates in the centrifugal pump, respectively. Additionally, the head coefficient, hydraulic efficiency and torque of the centrifugal pump are improved obviously with the redesign blade profile, while the cavitation number corresponding to the original head drop and the critical cavitation number of the modified impeller are both decreased gradually by up to 45.7% and 43.1% respectively as the ratio of tangent line (t) and the circle arc line (c) is increased. In addition, the much smaller low-pressure zone and cavitation area of modified impellers confirm that the suction performance of an impeller can be improved effectively with the modification method of the blade profile adopted in this study, which makes for the lesser cavitation damage and longer impeller lifetime.