- Volume 3 Issue 4
This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in prototype with different speeds of sound as well as in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics. Furthermore, in compressible simulation the amplification of pressure fluctuations is observed from the inlet of stay vane channels to the spiral case wall. Finally, the procedure is applied to a three-dimensional pump configuration in model scale with adapted speed of sound. Normalized Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher.
Compressible hydrodynamics;rotor-stator interaction;pump-turbine;unsteady CFD
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- Gagnon, J.M. and Deschenes, C., 2008, “Numerical Simulation of a Rotor-Stator Unsteady Interaction in a Propeller Turbine,” 24th Symposium on Hydraulic Machinery and Systems, Foz Do Iguassu.
- Guedes, A., Kueny, J.L., Ciaocan, G.D. and Avellan, F., 2002, “Unsteady Rotor-Stator Analysis of a Hydraulic Pump-Turbine: CFD and Experimental Approach,” 21st Symposium on Hydraulic Machinery and Systems, Lausanne.
- Flemming, F., Aschenbrenner, T., Jung, A. and Fisher, R.K., 2008, “Optimization of an Adjustable Speed Pump-Turbine using Unsteady Flow Simulations,” HydroVision 2008, Sacramento, CA, USA.
- Nennemann, B., Vu, T.C. and Farhat, M., 2006, “CFD Prediction of Unsteady Wicket Gate-Runner Interaction in Francis Turbines: A New Standard Hydraulic Design Procedure,” 23rd Symposium on Hydraulic Machinery and Systems, Yokohama.
- Zobeiri, A., Kueny, J., Farhat, M. and Avellan, F., 2006, “Pump-Turbine Rotor-Stator Interactions in Generating Mode: Pressure Fluctuation in Distributor Channel,” 23rd Symposium on Hydraulic Machinery and Systems, Yokohama.
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- Francis-Type Reversible Turbine Field Investigation During Fast Closure of Wicket Gates vol.140, pp.6, 2018, https://doi.org/10.1115/1.4039089
- Numerical Study of Pressure Pulsation of Centrifugal Pumps with the Compressible Mode pp.1993-033X, 2018, https://doi.org/10.1007/s11630-018-1071-7
- Effects of the Splitter Blade on the Performance of a Pump-Turbine in Pump Mode vol.2018, pp.1563-5147, 2018, https://doi.org/10.1155/2018/2403179