Hydraulic turbines are usually used to replace Joule-Thomson valves in petrochemical processes to reduce pressure, which can not only improve the overall efficiency, but also recover high-pressure liquid energy and improve energy efficiency. The overall performance of a hydraulic turbine is related to its efficiency of energy recovery. In order to make a quantitative and direct evaluation of the energy loss in the flow field of the hydraulic turbine, and to more accurately calculate the size and position of the hydraulic loss in the flow field, entropy production analysis theory based on the second law of thermodynamics is introduced for the analysis. The RNG κ-ε turbulence model is used to simulate the whole flow passage of the turbine, and compared with the experimental results. It is found that the calculated results are in good agreement with the experimental results. The entropy generation theory of the numerical simulation results is analyzed, and the entropy production of the guide vane and runner basin under different working conditions is obtained. The calculation results show that at the design operating point, the streamline distribution of the flow field of the runner basin is the best and the entropy production is the smallest. The entropy production of the guide vane and runner basin accounts for 56% and 44% of the total entropy production respectively, and the high entropy production in the runner is mainly distributed in the entrance area, which is caused by impact loss. There is a vortex in the flow field in the runner at the partial operating point, and the entropy production increases. The entropy production of the runner is related to the distribution of the velocity field of the internal flow field. At the off-design operating point, There are bad-behaved flow fields in the runner basin, which leads to an increase in hydraulic loss caused by turbulent pulsation, accompanied by an increase of entropy production. The results show that the entropy production theory has obvious advantages in hydraulic loss assessment and can accurately locate the source of hydraulic loss.
Key words：
hydrodynamic turbine runner; numerical simulation; entropy production theory
HUANG Ning, LI Zhenlin. Application of entropy production theory in flow field analysis of hydraulic turbines. Petroleum Science Bulletin, 2020, 02: 269-276.
