Blade Number Effects in Radial Disc Pump Impellers: Overall Performances with Cavitation Sensitivity Analysis

Abstract

Straight radial impeller disc pumps are widely used in several industrial applications for hard-to-pump working flow media, such as two-phase inlet conditions, either including non-miscible bubbles or solid particles with a high concentration within the main working flow. Compared with conventional pump designs, these pumps have not been widely studied, because of their particular simple design and low efficiency values that can however reach a maximum value of 0.5 with a good pressure increase in single-phase conditions. Regarding this, no basic analysis has been performed to build one-dimensional design rules considering the relative effects of design parameters proper to these unusual designs like the blade number, blade height and disc spacing. This step is an important one for two-phase flow performance evaluations which are usually derived from single-phase ones as for conventional pumps. Two different disc pump designs with, respectively, 8 and 10 radial blades, are numerically and experimentally investigated. Experimental investigations are performed in an open loop tap water test facility, under various working conditions, combining flow rate and rotational speed variations. The overall pump performances are compared and analyzed, including cavitation onset phenomena that have been found to influence the experimental performances of both pumps. The overall performance modification between both impeller designs is analyzed. Comparisons between CFD and experimental results give reliable results and can be considered to cover a sufficiently wide range of design parameters allowing us to build future adapted design rules for such specific designs.