The effects of viscoelastic fluid on the cavitation inception and development within a centrifugal pump: An experimental study

Abstract

Cavitation in a transparent centrifugal pump has been experimentally investigated using viscoelastic fluid. Viscoelastic fluids are aqueous solutions of polyacrylamide with different concentrations of 100, 200, and 400 ppm at room temperature. The cavitation inception and the bubble population through the blade passages were extracted using two different methods: (a) visually observing the population of bubbles in the flow and (b) pump characteristic curves analysis. The results illustrated that the polymer concentration, cavitation number, and degradation can dramatically affect the bubble initiation and development. Bubble initiation was postponed in the case of polymer solutions and this effect was more significant in higher concentrations. Besides, at the same conditions, the population of the bubbles in the polymer solutions significantly decreased compared to the water, especially at higher concentrations. This effect was decreased with decreasing the cavitation number. Also, the fresh polymer solutions had lower critical cavitation numbers in comparison with the tap water. In addition to the fresh polymer solution, the effect of the degradation was investigated in the current study, too. Results showed that with degradation, bubble initiation occurred sooner and the population of the bubbles significantly increased compared to the fresh solutions.