Axial Turbine CFD

This study shows fully an automated workflow of performing a complex CFD analysis of an axial turbine using TCFD®

TCFD® Main Page - Download This Tutorial - Turbine Results Report


TCFD® automated workflow


CFD SUPPORT introduces the new generation of CFD simulations. TCFD® brings an extreme increase of productivity to CFD simulations. TCFD® is extremely popular project, because it successfully merged benefits of an open-source (perpetual, unlimited users, jobs, and cores, customizable, ...) with benefits of commercial codes (professional support, well tested, ready for the industry, robust, accurate, automated, GUI, ...).

TCFD - Turbomachinery CFD scheme automated workflow

TCFD® is fully automated, it can run the whole workflow by a single command: data input, new case is written down, mesh is created, case is set-up, case is simulated, results are evaluated and the results report is written down. Both GUI and batch mode. Data in - data out. TCFD® is mainly focused on supporting the engineers in their real value added work. TCFD® is fully automated and the beauty of TCFD® is that it is the user who decides how deep to dive into a CFD or not at all. And all the options remain open at the same time.


The input data

The surface model data in .stl file format together with physical inputs are loaded in TCFD®. Other option would be loading an external mesh in OpenFOAM® mesh format, or loading an MSH mesh format (Fluent mesh format). This CFD methodology employs a multi component approach, which means the model is split into a certain number of regions. In TCFD® each region can have its own mesh and individual meshes comunicate via interfaces.

Axial turbine Full Wheel Stator Rotor turbomachinery CFD view 2      Axial turbine Full Wheel Stator Rotor turbomachinery CFD view 1      Axial turbine Full Wheel Stator Rotor turbomachinery CFD view 3


The Mesh

In this particular case the Axial turbine model is split into three components. The Spiral, the Impeller and the Drafttube. Each component has its own mesh. All the meshes are created automatically for each component within snappyHexMesh. Any number of model components is allowed, for example a typical Axial turbine might have a five component alternative: Spiral, Stay, Guide, Impeller and Drafttube.

Axial turbine Full Wheel Stator Rotor turbomachinery Mesh CFD view 3      Axial turbine Full Wheel Stator Rotor turbomachinery Mesh CFD view 1      Axial turbine Full Wheel Stator Rotor turbomachinery Mesh CFD view 2

In any CFD simulation, there is always big question how fine mesh is needed for ceratin level of CFD results. In rotating machinery there is usually clear trend observed: the finer mesh leads to slightly higher efficiency.

CFD axial Mesh segment run mass flow rate


Easy to test the mesh sensitivity

In practise the rough mesh with no boundary layer (CPU time: 4 core*hours/single point) can give the same results as the fine mesh with boundary layer (CPU time: 20 core*hour/point). So finally, the rough mesh effect can eliminate the lack of boudary layer. Anyway, with fully automated workflow it is easy to make many tests to callibrate to actual machine.




The component graph

Any project simulated in TCFD® has its component graph. The component graph shows how the components are organized - the model topology. What is the inlet, the outlet and how the components are connected via interfaces.


TCFD manifold tcfd tutorial component graph


CFD Simulation Set-up

  • Compressible flow model
  • Steady-state flow model
  • Medium: Steam (ideal gas)
  • Dynamic Viscosity: μ = 2.4e-5 [Pa.s]
  • Rotation speed: 3000 [RPM]
  • Flow Rate: 365 [kg/s]
  • Interface: mixingInterface (radial averaging)
  • Turbulence Model: k-ω SST
  • Mesh: blockMesh
  • Mesh Cells: 765204
  • Mesh Average y+: 257 [-]
  • CPU time: 4.5 [core*hours/point]

For more details of CFD Simulation Set-up see TCFD® Manual.


TCFD Axial Turbine grapgical interface model


Running CFD Simulation

The simulation can be run on any number of parallel processors. Immediately after the simulation is started the user can follow the progress of all the important quantities: flow rates, residuals, efficiency, torque, or pressure difference. This run-time functions give the user valuable information of the convergence and also the availability to stop the simulation before its standard end.

turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces

The workflow computes automatically complete characteristics point by point.


Every simulation performed in TCFD® has its report in .html format: Axial  Turbine Report Example.


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces




Visual Postprocessing using Turbo Blade Post

The simulation results are examined in ParaView (included in any of OpenFOAM distributions). ParaView is CFD postprocessing tool providing all standard features for analyzing CFD data.


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces

CFD Support developed special extension to ParaView for postprocessing rotating machinery: Turbo Blade Post which is special set of filters for ParaView to enable for example blade-to-blade view, or meridional average. Turbo Blade Post detailed manual is available on-line: Turbo Blade Post Manual


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces


Within Turbo Blade Post the impeller mesh can be unwrapped to be able to slice the computed quantities of the same height along the blade. With such a unwrapped mesh it is also possible to plot quantities around the blade at the certain height.


turbomachinery CFD Axial turbine total pressure per interfaces        turbomachinery CFD Axial turbine total pressure per interfaces

Another Turbo Blade Post function is Meridional Average which creates a meridional plane of circumferential averages of simulated quantities.

turbomachinery CFD Axial turbine total pressure per interfaces



See also other TCFD® simulation examples:

Axial Pump
Centrifugal Pump
Axial Fan
Centrifugal Fan
Axial Compressor
Centrifugal Compressor
Axial Turbine
Centrifugal Turbine
Francis Turbine
Kaplan Turbine
Manifold
Ship Hull Propeller
Valve
Wind Turbine
Valve



Please contact us for further information.





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