Unsteady Rotor-Stator Simulation of the U9 Kaplan …...Unsteady Rotor-Stator Simulation of the U9...

Chalmers University of Technology

Svensk Vattenkraft Centrum - SVC

Unsteady Rotor-Stator Simulation of the U9 Kaplan Turbine Model

Olivier Petit, Håkan Nilsson Chalmers University

6th OpenFOAM workshop

Penn State University, USA

13-16 June 2011



•  Develop OpenFOAM as the future first choice for industrial CFD in water turbine applications ( validate new implementations useful for Turbomachinery applications)

•  Interact with the experimental project, in order to improve the flow in the U9 model



•  Prototype located in Porjus, consist in a Kaplan turbine.

•  Designed to be able to perform detailed measurements on a real scale turbine/generator unit.

•  1:3.1 scale model of the U9 turbine is set up at Vattenfall Research and Development in Älvkarleby.

U9 unit, Porjus, Sweden

U9 scale model, Älvkarleby, Sweden



•  Create a detailed measurements database that can be used to validate future numerical simulations.

•  Investigate the impact on the flow of the curved pipe at the inlet of the spiral casing.



• U9 spiral casing: mesh of 5 millions cell, block structured hexaedral, realized with ICEM-HEXA.

• Y+ value between 50-100.



• U9 Runner: mesh of 100 000 cell, block structured hexaedral, realized with ICEM-HEXA.




• U9 draft tube: mesh of 1 million cell, block structured hexaedral, realized with ICEM-HEXA.




A

A

A-A



• At the inlet of the spiral casing, velocity profiles measured with LDA technique at 5 horizontal profiles(Py 1-5), and 1 vertical (Pz). • Results presented in dimesionless form using Rinlet=0.316m, and vBulk=Q/Ainlet , Q=0.71 m.s-1

• Comparison between experimental and numerical results are shown for the best efficiency point, Q=0.71 m/s, and alpha=26° (angle of the guide vanes)



•  Similar behaviour between experimental and numerical results.

•  Difference between numerical and experimental prediction of the flow can be due to the turbulence model: the k-ε model is not accurate enough to give a good prediction of the flow in a curved pipe.



•  Reference point is at the wall for both windows.

SI SII



Inlet boundary conditions

• The reference point is located on the centreline. • Axi-symmetric profile is taken at the inlet from experimental data provided by Berhanu Mulu



P1_a P1_c

P3_a P3_c



•  Inlet boundary condition needs to include the unsteadiness of the wakes to predict accurately the flow in the draft tube • Radial velocity must be included to get a good approximation of the flow • Better turbulence model should predict more accurately the flow features.



•  mesh of 12 million cell, block structured hexaedral, realized with ICEM-HEXA.

•  7 GGI interfaces, linking different part of the U9 model

•  TransientSimpleDyMFoam, OpenFOAM-1.5-dev, k-ε model

•  Inlet boundary condition: plug flow with Q=0.71 m/s

•  Turbulence parameters calculated so that I=0.1, and νT/ν=10.

•  CFD tool is OpenFOAM. Pressure and velocity probes are created to monitor the flow in the spiral casing and in the draft tube.



•  The prediction of the flow before the runner is rather accurate

•  A separation of the flow occurs after the runner blades, pushing the flow against the shroud . The y-plus value needs to be lowered in the runner area.



•  Focus on the U9 runner to get proper y+ value, and proper flow behaviour

•  Pressure, velocity analysis of the whole U9 model and comparison with the measurement data.

Thank you for your attention!

Unsteady Rotor-Stator Simulation of the U9 Kaplan …...Unsteady Rotor-Stator Simulation of the U9...

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