Abstract
To study the influence of the blade entropy production range on the efficiency of a tubular turbine under coassociated conditions, the renormalization group K–ε turbulence model was used to simulate the full flow passage of the tubular turbine based on the Navier–Stokes equation, and the blade interface was analyzed using the eddy analysis method and entropy production theory. The results reveal that there is a strong correlation between the size of the high-entropy production area and the level of association. If the level of association is high, the size of the high-entropy production is small, and the turbine efficiency is high. Furthermore, if the level of association is low, the size of the high-entropy production area is large, and the turbine efficiency is low. Under small opening and small flow conditions, the blade entropy generation is due to the sharp change in the velocity gradient caused by the vortex on the blade. Under large opening and large flow conditions, the blade entropy production is mainly due to the friction loss caused by the impact of high-speed water flow.
Highlights
Greenhouse gas emissions have led to global warming, and energy conservation and emission reductions have become a global consensus (Lu, 2021)
This study considers the Chaijiaxia cross-flow turbine unit as the research object and conducts numerical simulations to obtain the magnitude of turbine efficiency under the coassociated conditions of different flow rates
Ghorani et al (2020) used the entropy production theory for pump turbines to demonstrate that turbulence is the main source of entropy production
Summary
Greenhouse gas emissions have led to global warming, and energy conservation and emission reductions have become a global consensus (Lu, 2021). The Ninth Meeting of the Central Finance Committee proposed incorporating carbon peaking and carbon neutrality into the overall layout of ecological civilization construction and recommended the construction of a clean, lowcarbon, safe, and efficient energy system (Hongchun, 2014). The flow pattern inside a turbine consists of laminar, turbulent, and turning flows. Under the effect of turbulent flow, the fluid microclusters exhibit vortex motion, resulting in viscous dissipation, which leads to a reduction in unit efficiency. In order to investigate the relationship between spin flow and energy loss inside the turbine, various approaches have been utilized. In order to investigate the relationship between spin flow and energy loss inside the turbine, various approaches have been utilized. Wentao (2014) used the large eddy simulation method and the calculation method of the evaporation/condensation cavitation model to conduct numerical simulations of the mixed-flow turbine and concluded that there was no strong swirl at the runner outlet under the rated opening, which could effectively improve the flow at the inlet of the tailpipe and reduce the pressure pulsation. Zhengwei et al (2004) analyzed the flow field of the entire passage of the bulb tubular turbine
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