Dean effect and performance analysis of the volute sectional shape of a pump as turbine based on enstrophy dissipation

Centrifugal pumps as turbines (PAT) can effectively balance efficiency and economy, becoming an important energy-saving technology to promote sustainable development. The sectional parameters of the volute, a crucial water diversion chamber and flow channel, affect the downstream flow condition and discharge capacity. In this paper, five distinct volute sectional shapes were designed. Based on the enstrophy dissipation theory, the energy loss mechanism in PAT was compared with the hydraulic loss by computational fluid dynamics (CFD), and the Dean effect in volute was theoretically analyzed. The results show that the maximum efficiency of the PAT equipped with Radius type volute is 4.91% higher than that of the original PAT, which can reduce the enstrophy dissipation power in the PAT. The Asymmetric type and Ellipse type volutes are not suitable for the PAT with a low specific speed. The viscous and inertial forces are altered by the volute sectional shape and the contraction capacity of each section. The fluid velocity gradient and the growth of the Dean vortex are the main sources of energy loss. The shock-induced turbulence loss accounts for the majority of the impeller's energy loss. The conclusions of this paper can inform the design and optimization of PAT.