Flow generated by a disc turbine. IV: Multiple impellers

Abstract

The three dimensional turbulent flow generated by multiple impellers was measured using a laser Doppler anemometer. The tank diameter was 300 mm with a flat bottom and provided with four T/10 baffles. Two impellers were mounted on the same shaft. A standard Rushton disc turbine (DT) and a pitched blade downflow turbine (PTD) were used as impellers. Two impeller combinations were studied: (1) DT-DT and (2) DT-PTD. The impeller diameter was 100 mm and the impeller speed was 5 r/s in all the cases. The impeller clearance from the bottom and the distance between the two impellers were varied over a wide range. The effect of these variables on the flow pattern has been presented. Energy balance has been established and the values of hydraulic efficiency and pumping effectiveness have been reported.