LDV Investigation of the Self Induced Pre-Swirl and Flow Visualization at the Centrifugal Pump Inlet and Outlet

Abstract

Turbulent swirling flow occupies attention of numerous researchers worldwide. In this paper are presented experimental results of the research of the self induced pre-swirl by the centrifugal impeller. Circumferential velocity was measured in two cross-sections by use of the one-component laser Doppler velocimetry (LDV) system. Flow visualization at the pump inlet, as well as at the pump outlet, was conducted by using the high speed camera Photron Fastcam SA1.1 and the LED light for illumination. Air bubbles were used for flow illumination, and silver coated particles for LDV measurements. Pump characteristics (head, volume flow rate and power) are, also, measured in the tested duty point. Pre-swirl is visualized, while almost developed uniform turbulent flow is documented at the pump casing outlet. By using LDV it was possible to identify almost solid body circumferential velocity profile at the pump inlet, only 0.5D upstream, where D is pipe inner diameter. So, the influence of the impeller suction is obvious. In paper is, also discussed statistics of the generated turbulence.