Experimental and Numerical Investigation of Centrifugal Pumps As Turbines

Installation of Pumps As Turbines (PATs) in Water Distribution Networks (WDNs) is a relevant topic in the field of innovative management of WDNs. In case of excess head over a WDN, PATs can be used for both pressure regulation and hydropower generation. Unlike traditional turbines, a PAT can be selected among a wide set of available models with lower investment and maintenance costs. On the other hand, PATs show a relatively narrow operating range, even though hydraulic and/or electrical regulations can be used. The main issue preventing the use of PATs is that performance curves are not available from manufactures. Thus, experimental and theoretical relations have been developed to predict the PAT performances and to simulate the internal fluid dynamics. To this end, Computational Fluid Dynamic (CFD) models are widely applied to both simulate the actual flow field of a machine and assess the efficiency improvements resulting from a geometry modification. In the present study, results from experimental and numerical investigations on different models of centrifugal PATs are discussed. A laboratory rig has been installed at the University of Naples Federico II to test both horizontal and vertical axis (single-stage and multi-stage) centrifugal PATs. The analysis was carried out by considering flow rates ranging between 10 and 50 l/s and head drops between 1 and 72 m. The generated power varied from few Watts up to 16.3 kW. The performance was assessed as a function of the number of stages and the motor Efficiency Class, and the reliability of analytic relationships from the literature was verified. Finally, experiments were compared with results of a CFD model, which showed slight differences against laboratory measurements.