Design, optimization, and flow characteristics of energy recovery turbines: A review

This study systematically examines energy recovery turbine (ERT) structural forms, four predominant design methods, hydraulic optimization, and flow mechanisms. Among these features, the pump as turbine (PAT) design method is widely adopted owing to the high availability of models and low cost, although its efficiency is subpar. While pump turbines and conventional turbine designs are more efficient, they are costly and pose challenges in obtaining parameters. New design methods offer the potential for reduced design costs. However, because of an incomplete theoretical framework, they remain in the initial research phase. Blade geometry (e.g. rounded leading edge, splitter blade) and guide vane design optimization can improve the flow separation and pressure pulsation and enhance the efficiency by 1–4%. Research on unsteady flow characteristics has shown that the dynamic and static interference and internal vortex evolution strongly influence ERT stability. The application of entropy generation theory has revealed that the flow channel, guide vane, and volute are regions of high energy loss, and that the boundary layer separation and eddy current are the main causes. Finally, the problems faced by turbine equipment in engineering applications are summarized, and research suggestions related to ERTs are provided through a comprehensive analysis.