Numerical investigation of energy loss in a centrifugal pump through kinetic energy dissipation theory

Abstract

In this study, energy loss within a centrifugal pump is investigated by post-processing three-dimensional unsteady flow field through kinetic energy dissipation theory. The three-dimensional unsteady flow field is predicted by solving unsteady Reynolds-averaged Navier–Stokes equations. The kinetic energy dissipation consists of three parts: averaged kinetic energy dissipation, turbulent kinetic energy dissipation, and near-wall revised kinetic energy dissipation. The total value variations of three kinetic energy dissipations in the centrifugal pump with flowrate are investigated and compared. Results show that with the increase in flowrate, the total near-wall revised kinetic energy dissipation gradually increases, the total turbulent kinetic energy dissipation first gradually decreases and then gradually increases, and reaches the minimum value at the design flowrate. The total averaged kinetic energy dissipation is less than the total turbulent and the total near-wall revised kinetic energy dissipations, and the total near-wall revised kinetic energy dissipation is larger than the total turbulent kinetic energy dissipation when the flowrate is larger than 0.75Q_des. The space variation of the near-wall revised kinetic energy dissipation with flowrate shows that large near-wall revised kinetic energy dissipation mainly occurs at the volute and transfers from the small cross-section casing to large cross-section casing and discharge pipe with the increase in flowrate. The space variations of the turbulent kinetic energy dissipation with time for three flowrates are also discussed. Results indicate that large turbulent kinetic energy dissipation near the volute tongue evidently changes with the rotation of the impeller, particularly in 0.5Q_des. The large turbulent kinetic energy dissipation gradually expands to the pressure side of the blade when the volute tongue gradually approaches the middle of the impeller blade passage. The large turbulent kinetic energy dissipation transfers from the impeller inlet and outlet to the volute tongue and discharge pipe with the increase in flowrate. The findings of this study can serve as guide to improve the design of centrifugal pumps.