AN LDA STUDY OF THE TURBULENT-FLOW FIELD IN A BAFFLED VESSEL AGITATEDBY AN AXIAL, DOWN-PUMPING HYDROFOIL IMPELLER

The turbulent flow of water in a cylindrical, baffled vessel with an a xial flow hydrofoil impeller, either a Chemineer HE3 (CHE3) or a Proch em Maxflo T (PMT), has been studied using a laser Doppler anemometer. Using ensemble averaging, the mean axial and radial flow and the assoc iated fluctuating components were obtained for the whole of the vessel ; plus similar data for the tangential component close to the impeller . Assuming axial symmetry, now rates were calculated as were flow numb ers and circulation now numbers. Power numbers were also determined. A ll the data obtained were used to compare the circulation efficiency o f the two hydrofoils plus a pitched blade and a Rushton turbine. This comparison showed that the CHE3 required a power input of about 2/3 of that for the PMT and about 1/3 of that for the pitched blade and Rush ton turbine to obtain the same axial-radial circulation in the tank.