Transient numerical analysis of rotor–stator interaction in a Francis turbine |
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| Affiliation: | 1. Flow Informatics Lab, Department of Mechanical & Energy System Engineering, Korea Maritime & Ocean University, Busan, South Korea;2. Department of Mechanical Engineering, School of Engineering, Kathmandu University, Dhulikhel, Nepal;3. Department of Mechanical and Energy System Engineering, Korea Maritime & Ocean University, 606-791 Busan, South Korea;1. Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway;2. Department of Mechanical Engineering, Kathmandu University, Dhulikhel, Nepal;1. Indian Institute of Technology Roorkee, India;2. Luleå University of Technology, Sweden;3. Norwegian University of Science and Technology, Norway;1. Research Group of Fatigue and Surfaces, School of Mechanical Engineering, Universidad del Valle, Cali, Colombia;2. EPSA E.S.P. A CELSIA Company, Colombia;1. Laboratory of Energetic Mechanics (LEMI), Faculty of Engineering, University of Boumerdes, 35000, Boumerdes, Algeria;2. Laboratory of Energetic Mechanics and Conversion Systems, Faculty of Mechanical Engineering, University of Sciences and Technology Houari Boumediene, BP32 El-Alia, Bab-Ezzouar, 16111, Algiers, Algeria |
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| Abstract: | Pressure fluctuation due to rotor–stator interaction and occurrence of vortex rope in draft tube at partial load operation are obvious phenomena in Francis type reaction hydro turbines. These hydrodynamic effects are important issues and should be addressed during the design of hydraulic machines. A 3-dimensional transient state turbulent flow simulation in the entire flow passage of a 70 kW-Francis turbine having specific speed of 203.1 is conducted to investigate the rotor–stator interaction by adopting kω based SST turbulence model. The commercial 3D Navier–Stokes CFD solver Ansys-CFX is utilized to study the flow through this vertical shaft Francis turbine in its stationary and transient passages, at 100% optimum load and 72% of part load. The investigated turbine consists of a spiral casing with 16 guide vanes, 8 stay vanes, a runner with 13 blades and a draft tube. With a time step of 2° of a rotational period of the runner for 10 full rotations, the time dependent pressure and torque variations are monitored at the selected locations during the unsteady state calculation. A periodical behavior is observed for the pressure distribution in guide vanes, runner blades and torque in the runner blades. The pressure distribution curve in runner blades reveals the two dominating frequencies – the lower peaks due to runner speed and the upper peaks corresponding to the number of guide vanes interacting with the flow. The flow acceleration toward inside of the runner is depicted by the expanding wakes behind the stay vanes. Vortex rope is observed in draft tube, downstream the runner, at part-load operation. |
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| Keywords: | Francis Unsteady flow Rotor–stator interaction Vortex rope CFD |
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