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CFD applied to Turbo machinery
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CFD APPLIED TO TURBOMACHINERY
Martin Kessler, PhD
07/04/2011
PAGE 2Examples - Turbomachinery
PAGE 3Examples - Hydro
Power and
Efficiency
Cavitation
Flow pattern
PAGE 4Examples - Wind
Power and
Efficiency
Flow pattern
PAGE 5Topology
• All turbomachines are
topologically identical
– Just variations on a theme
– Lends perfectly to design
systems and parametric
models
• Machines differ by
changing
– Hub/shroud shape
– Blade leading and trailing
edge shape and location
– Blade wrap or angle
– Number of blades
– Rate of rotation
Hub
Shroud
Blade
PAGE 6What is CFD (Computational Fluid Dynamics)?
• CFD requires a computational model build as a representation of physical problem
• Usually begins from a CAD import operation
• Mesh generation for fluid region (domain for CFD analysis).
• Solve mathematical equations
• Post-processing of results
HVAC ducts - geometry
Mesh Results
Cleaning
PAGE 7CFD Methodology
Eqn.
continuidade 1
x-mom. u
y-mom. v
energia h
Fluid flow region
discretized into
finite volumes
(computational
mesh)
Control
volume
Solver is usually based on finite volume method
Domain is dicretized into control volumes
Momentum, mass and energy balance
equations are discretized into algebraic
equations
All equations are solved in order to have the
flow solution
VAAV
dVSdddVt
AAV
transitório convecção difusão geração
PAGE 8ANSYS Turbo System Environment
Geometry
Blade Modeler
Meanline Tools
BladeGen
DesignModeler
with
BladeEditor
Mesh
TurboGrid
ANSYS Meshing
ICEM CFD
Analysis
Vista TF
ANSYS CFX
FLUENT
ANSYS FEA
Parameterization
Design Exploration
ANSYS Workbench
PAGE 9ANSYS Workbench Workflow - CFD
BladeModeler
TurboGrid
TurboPre
CFX Solver
TurboPost
PAGE 10ANSYS Workbench Workflow
Integrated Process
Within ANSYS Workbench
From initial component
designs to accurate complete
system analysis
BladeModeler
TurboGrid
TurboPre
CFX Solver
TurboPost
Structural Extensions
Mechanical Analysis
PAGE 11ANSYS Workbench Environment
PAGE 12
Radial
Impeller
Simple
Axial
Radial
Diffuser
Axial
Radial
Turbine
BladeGen: Templates Approach
Radial
Deswirl
Vane
PAGE 13
• Initial Blade Setup
– Can define wrap angle, thickness, and number of blades
– Properties will be constant from hub to shroud
User will need to modify properties on spanwise layers
BladeGen: Template Approach
PAGE 14
• Initial Blade Setup
– Alternatively, blade can be defined by defining pressure and suction sides
BladeGen: Template Approach
PAGE 15BladeGen: Design Environment
Meridional View Auxilliary View
Angle View Thickness View
PAGE 16BladeModeler - DesignModeler
• DesignModeler
– Automatic Fluid Zone Creation
– Create assemblies including “non-turbo” components
PAGE 17Single Component: Extent
Inlet / outlet too close Inlet / outlet ½ blade chord away
PAGE 18Mesh Types - Meshing
• Tet Mesh and Tet/Prism hybrid
• Hex Mesh
PAGE 19Mesh Types - Meshing
• Multiple domain: rotor (blue) + stator (red)
PAGE 20Grid Quality Guidelines
• Grid smoothness:
– Avoid sudden changes in grid density
“Bad” “Good”
PAGE 21ANSYS TurboGrid
• Automated topology & mesh
generation
• Highly defaulted, manual user
controls
• Fast volume meshing & pre-
mesh at 2D layers
• Pre-defined topologies:
– H, J, C, L
• Layers, user control points,
edge split controls, …
• Automatic Topology &
Meshing (ATM) Method
PAGE 22ATM Method - Hub Mesh
PAGE 23CFX Turbo Mode
CFX Turbo mode
allows for the
configuration of
the turbomachine
Type of machine:
pump
Axis: z
PAGE 24CFX Turbo Mode
Rotation
Region information
PAGE 25CFX Turbo Mode
Fluid type
Analysis type
Boundary conditions
Solver parameters
PAGE 26CFX Turbo Mode
Periodic boundaries
PAGE 27CFX Solver
PAGE 28Qualitative Post-Processing – CFD-Post
3-D
View
Blade-to-Blade
View
Meridional
View
PAGE 29
Volute
Rotor
Suction
Full Domain
Examples of Cases with Our Partners – CEMIG
PAGE 30Examples of Cases with Our Partners – CEMIG
• Computational Domain: ~600.000 nodes
PAGE 31Examples of Cases with Our Partners – CEMIG
• Rotor Computational Domain: ~170k nodes (1 blade)
•14 blades: ~2.4M nodes
PAGE 32
ModifiedBaseline
Examples of Cases with Our Partners – CEMIG
PAGE 33Examples of Cases with Our Partners – CEMIG
ModifiedBaseline
PAGE 35Examples of Cases with Our Partners – CEMIG
PAGE 36
