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Comparison of steady and unsteady simulation methodologies for predicting no-load speed in Francis turbines
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 Title & Authors
Comparison of steady and unsteady simulation methodologies for predicting no-load speed in Francis turbines
Hosseinimanesh, Hossein; Devals, Christophe; Nennemann, Bernd; Guibault, Francois;
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No-load speed is an important performance factor for the safe operation of hydropower systems. In turbine design, the manufacturers must conduct several model tests to calculate the accurate value of no-load speed for the complete range of operating conditions, which are expensive and time-consuming. The present study presents steady and unsteady methods for calculating no-load speed of a Francis turbine. The steady simulations are implemented using a commercial flow solver and an iterative algorithm that relies on a smooth relation between turbine torque and speed factor. The unsteady method uses unsteady RANS simulations that have been integrated with a user subroutine to compute and return the value of runner speed, time step and friction torque. The main goal of this research is to evaluate and compare the two methods by calculating turbine dynamic parameters for three test cases consisting of high and medium head Francis turbines. Overall, the numerical results agreed well with experimental data. The unsteady method provided more accurate results in the opening angle range from 20 to 26 degrees. Nevertheless, the steady results showed more consistency than unsteady results for the three different test cases at different operating conditions.
No-load speed;runaway speed;Francis turbine;steady-state simulation;unsteady state simulation;
 Cited by
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