Analysis of hydraulic loss of the pump-jet with accelerating and decelerating ducts via entropy generation theory

Pump-jets serve as critical propulsion systems for underwater vehicles, directly impacting navigation safety and energy efficiency. Traditional pressure-drop analysis methods, while widely adopted, exhibit limitations in spatially resolving localized energy dissipation mechanisms. This study implements entropy generation theory to systematically evaluate irreversible energy losses in pump-jet, with particular emphasis on quantifying the spatial distribution and magnitude of hydraulic losses. Through rigorous numerical investigations of accelerating and decelerating duct configurations with varying camber and attack angles, comparative analyses of energy characteristics are conducted across distinct pump-jet components. The results demonstrate that entropy generation theory proves advantageous when assessing the energy characteristics of pump-jet. Compared to accelerating duct pump-jet, the stator and pre-stator of decelerating duct pump-jet absorb a larger share of hydraulic losses, demonstrating superior hydrodynamic performance. Flow characteristics reveal that the variation of f and alpha leads to the significant influence on the entropy production in the flow field, while the instability mechanism of impeller and stator trailing vortices also share prominent diversity. Thus, f and alpha can serve as core parameters to distinguish between accelerating and decelerating ducts. Selecting appropriate parameters based on different operating conditions can significantly enhance performance and safety. Overall, this study provides thermomechanical guidelines for performance optimization through strategic geometric parameter selection under diverse operational conditions.