Consistent Improvement of the Charging Technology of Audi TFSI Engines by CFD
K. Vehreschild, Audi AG Ingolstadt
4th European Automotive Simulation Conference - EASC 2009
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Summary
Contents
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
1
Cooling
►Water jacket►Components (Thermostat)►Thermal management
Introduction
CFD areas in engine development
Oil►Oil circuit
►Crank caseventilation
Gas exchange► Intake / exhaust
manifold design►Gas dynamics►Valve lift curves►Boundary conditions
for 3D CFD / FEA
Engine-thermodynamics►Intake manifold►Exhaust manifold►Intake / exhaust ports►Charge motion flap
Car components►Air intake ducts, air filter
►Charge air ducts, intercooler
►Exhaust system
►Water / spray in inlet duct
►Deep wading►Cooling system
Exhaust gas after-treatment► Catalyst► O2 sensor► Secondary air injection
Combustion TFSI,TDI►Charge motion►Injection►Combustion►Oil dilution
Charging technology TFSI, TDI►Turbine, compressor►Supercharger
Introduction
V6 supercharged engine
► In August 2008 the 3.0 TFSI, a
supercharged V6 engine was
introduced
► For the new Audi S4 e.g., this high
power V6 replaces the naturally
aspirated 4.2 FSI (V8), reducing
weight and fuel consumption
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
2
Introduction
CFD covered topics of the supercharger device
Flow through supercharger
Introduction
Motivation for complex supercharger flow investigation
► Focus on basic flow phenomena rather than on detail optimization
► Airflow into and out of the supercharger
► Flow phenomena inside the supercharger
► Closer look at the compression
► If possible, acoustic excitation mechanisms
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
3
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Summary
Contents
CFD modelling approach
Domains
► Modelling was done in collaboration
with Ansys
► Moving mesh domain inside the rotor
drillings, everything else is a static
tetrahedral mesh
► Housing can be exchanged easily
► Intercoolers modelled as porous media
Yellow: Moving mesh domainGrey: Stationary domainRed / Blue lines: Interface bordersBoxes: Intercoolers
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
4
RotorsRotors
CFD modelling approach
Moving mesh domain
► Rotors are more or less cogwheel-
shaped and longitudinally extruded
with a screw angle of 160°
► Meshing is basically 2D , made out of
several parameter based key meshes
► In between the key mesh positions
mesh morphing is used to interpolate
► 3d mesh is just a sequence of 2D
meshes in different angular rotor
positions
► A 1-1 interface is set in between the
rotors to connect both sides to control
the deformation
► No user subroutines, only CCL
CFD modelling approach
Moving mesh domain
Dividing surface with 1:1 connection
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
5
CFD modelling approach
Moving mesh domain
CFD modelling approach
CFD model setup
► Stationary boundary conditions at inlet and outlet
► Investigated operating points:
► 10000 rpm / full load (bypass throttle closed)
► 5625 rpm / full load (bypass throttle closed)
► 5625 rpm / part load (bypass throttle open)
► 4 revolutions of the rotors were calculated
► Rotation per time step: 0.6°
► Calculation time: approx. 4 days on 12 processors
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
6
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Air inlet
► Pressure build up
► Outlet flow
► Summary
Contents
Results
Air Inlet
56%
44%49% 51%
InletOutlet
50% 50%50% 50%
InletOutlet
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
7
Results
Air inlet
Blow holes connect all chambers in the suction part
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Air inlet
► Pressure build up
► Outlet flow
► Summary
Contents
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
8
Results
Pressure build up (full load)
0 90 180 270 360 450
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
0 90 180 270 360 450
0
10
20
30
40
50
60
70
80
90
100
Chamber Pressurech
am
be
r p
ress
ure
[b
ar]
rotor angle [°]
Inlet Area Chamber Volume Outlet Area Blow hole
re
lati
ve v
olu
me
/ a
rea
[%
]
rotor angle [°]
Upper blow holes connect chambers –continuous pressure rise
Results
Pressure build up (full load)S
tati
cp
ress
ure
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
9
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Air inlet
► Pressure build up
► Outlet flow
► Summary
Contents
Results
Outlet flow
Part load: medium mass flow
► Strong axial flow direction
► forced upwards by left wall
► Zigzag flow
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
10
Results
Outlet flow
Full load: High mass flow
► Vortices at triangle top
caused by outlet pocket
► High mass flow forces air to
go upwards instead of axial
► No apparent zigzag flow, but
left-right direction change
► Introduction - Charging technology and CFD at Audi
► CFD modelling approach - Supercharger 3.0 TFSI
► Results - Transient flow phenomena
► Air inlet
► pressure build up
► Outlet flow
► Summary
Contents
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
11
Summary
► The transient simulation of the 3.0 TFSI supercharger module is one sophisticated
example for CFD applications in the development of charging technology at Audi.
► Besides this complex moving mesh simulation many other "standard" CFD topics
were applied during the development of the module.
► The key aspects of this consistent CFD improvement of charging technology in
general are:
► "tailored CFD process“: optimum definition of CFD topics for each separate
development project, with respects to development targets, time-scales, etc.
► Development of new methods "on-the-fly" : continuous improvement of CFD
efficiency, accuracy and portfolio directly in the process chain - according to the
necessities of the technology development
► Development expertise of CFD experts : despite the fact that CFD experts have
to be CFD experts, nowadays they also have to be experienced developers
EASC 20094th European Automotive Simulation Conference
Munich, Germany6-7 July 2009
12