Visualization of Vortex Core inside an Impeller Passage of a Centrifugal Pump

Abstract

When a swirling flow enters a centrifugal pump, the flow inside the impeller passages is subject to a rapid change due to the interaction of the vortex core and the impeller blades. Using pressure transducers, the instantaneous pressures on the blade surface were measured and the pressure fluctuation due to this vortex core was analyzed.
In order to visualize the collapse of the vortex core inside the passage, a small quantity of air was introduced into the suction pipe and photos of air bubbles inside the impeller passage were taken by detecting the circumferential position of the eccentric vortex core. The nature of the pressure change was found to depend upon the direction of the swirling flow component.