Study of the Hydraulic Performances of Two Inducers in Water—CO₂ Mixture—Toward Performance Improvement With Suppression of Prerotation

The inducers increase the pressure available at the inlet of the impellers of centrifugal pumps. This technological solution may induce instabilities, such as prerotating flow at partial flow rates. The scientific literature offers studies on the cavitation in the inducers, as well as on the associated instabilities. However, studies describing devices that improve the behavior in these unstable regimes are rare. This is particularly true for fluids like aviation fuels or liquids with dissolved gases. In this work we expose, an experimental study for two axial inducers carried out at low flow rates in cavitating and noncavitating regimes in a closed-loop equipped with a transparent test pipe. The working liquid is water with and without dissolved CO₂. We employ a camera and a high-speed camera to take the photographs of the dynamics of the cavitation structures. The experimental campaign provided results of head breakdown comparison. The added dissolved CO₂ gas at a concentration of 300 mg L^–1 does not change the overall inducers' performance in noncavitating regime. The paper presents also the impact of some of inducers' geometrical parameters on their cavitating performance. The authors observed prerotating flow instability, which they tried to decrease by incorporating a grooved ring into the inlet side of the inducers. It is found that prerotating structures are much less developed in the upstream when a grooved ring is employed.