Entropy production analysis for vortex rope of a Francis turbine using hybrid RANS/LES method

被引:36
作者
Yu, Zhi-Feng [1 ]
Yan, Yan [1 ]
Wang, Wen-Quan [2 ]
Liu, Xing-Shun [1 ]
机构
[1] Kunming Univ Sci & Technol, Fac Civil Engn & Mech, Kunming 650500, Yunnan, Peoples R China
[2] Sichuan Univ, Coll Water Resource & Hydropower, State Key Lab Hydraul & Mt River Engn, Chengdu 610065, Peoples R China
关键词
Francis turbine; Entropy production; Flow losses; Vortex rope; DDES method; DETACHED-EDDY SIMULATION; TURBULENT MIXED CONVECTION; PUMP-TURBINE; DRAFT TUBE; UNSTEADY-FLOW; HEAT-TRANSFER; MODEL; FLUID; WIND;
D O I
10.1016/j.icheatmasstransfer.2021.105494
中图分类号
O414.1 [热力学];
学科分类号
摘要
The precessing vortex core in the draft tube of Francis turbine is investigated using entropy production method. The high-fidelity Delayed Detached Eddy Simulation (DDES) method with SST k-omega turbulence model is used to acquire the entropy dissipative components of the flow, and the Q-criterion is selected to evaluate the vortex cores inside the draft tube under different operating conditions, separately. The results show that the numerical simulation is in good agreement with the experimental data obtained from the model test. It is found that the vortex motion, separation flow and shock phenomenon are considered to be hydrodynamic factors for the formation of entropy. Furthermore, draft tube accounts for the greatest proportion of entropy production, which is ascribed to the vortex rope. Vortex rope will rotate in the same direction as the runner, but the rotational speed is lower, resulting in low frequency pressure pulsation with large amplitude in the draft tube. It is concluded that the key reason why great energy dissipation is caused in the draft tube is that the vortex rope is transporting continuously towards the downstream, especially when the turbine deviating from optimum operating point.
引用
收藏
页数:21
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