Author(s): Ahmed Laouari, Adel Ghenaiet
Linked Author(s): Ahmed Laouari
Keywords: CFD, francis turbine, hydraulic performances, pressure oscillation, unsteady flow
Abstract: Computational Fluid Dynamics (CFD) analysis is a very useful tool for predicting performances at different operating conditions of hydraulic machinery. All theoretical methods for predicting the performance merely gives a value, and one is unable to determine the root cause for the poor performance. Due to the development of CFD code, one can get the performance value as well as observe the actual behavior of the flow in the domain. Analysis and variation of performances can be found out by using CFD analysis. Pressure ?uctuation 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 3D transient state turbulent ?ow simulation in the entire ?ow passage of a Francis turbine was conducted to investigate the rotor-stator interaction by adopting k-? base SST turbulence model. The commercial 3D Navier-Stokes CFD solver Ansys-CFX was utilized to study the ?ow through this horizontal shaft Francis turbine in its stationary and transient passages, at small flow, optimal, and high flow rate. The investigated turbine consists of a spiral casing with 6 guide vanes, a runner with 10 blades and draft tube. A periodical behavior was observed for the pressure distribution in guide vanes, runner blades and torque in the runner blades. Vortex breakdown occurred in the draft tube at small flow rate operation of the turbine. The rotational frequency of the vortex was predicted for the rotational frequency of the runner
Year: 2017