Hydraulic and rotor-dynamic interaction for performance evaluation on a Francis turbine
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This paper proposes a new methodology to evaluate the technical state of a Francis turbine installed in a hydroelectric plant by coupling computational fluid dynamics (CFD) and rotor-dynamic analysis. CFD simulations predicted the hydraulic performance of the turbine. The obtained field forces, due to the fluid-structure interaction over the blades of the runner, were used as boundary condition in the shaft rotor-dynamic numerical model, which accurately predicted the dynamic behavior of the turbine's shaft. Both numerical models were validated with in situ experimental measurements. The CFD model was validated measuring the pressure fluctuations near the rotor-stator interaction area and the torque and radial force in the shaft using strain gages. The rotor-dynamic model was validated using accelerometers installed over the bearings supporting the shaft. Results from both numerical models were in agreement with experimental measurements and provided a full diagnose of the dynamic working condition of the principal systems of the turbine. Implementation of this methodology can be applied to further identify potential failure and improve future designs.