An experimental investigation of the flow fields within geometrically similar miniature-scale centrifugal pumps

Flow fields within two miniature-scale centrifugal pumps are measured and analyzed to facilitate an understanding of how scaling influences performance. A full-scale pump, of impeller diameter 34.3 mm and blade height 5 mm, and a half-scale version were fabricated from a transparent material to allow optical access. Synchronized particle-image velocimetry (PIV) was performed within the blade passage of each pump. Pressure-flow characteristics, hydrodynamic efficiencies, and high-resolution flow field measurements are reported for six rotational speeds over a Reynolds number range 706-2355. Fluidic phenomena occurring in the impeller passage at both pressure and suction surfaces are identified. Efficiencies are evaluated from direct measurement to be between 10% and 44% and compared with inner efficiencies calculated from the PIV data. Hydrodynamic losses as a percentage of overall efficiency increase from 12% to 55% for 2355≤Re ≤706. Slip factors, in the range 0.92-1.10, have been derived from velocimetry data.