4th European Automotive Simulation Conference - EASC 2009

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1 Consistent Improvement of the Charging Technology of Audi TFSI Engines by CFD K. Vehreschild, Audi AG Ingolstadt - EASC 2009 Contents Introduction - Charging technology and CFD at Audi CFD modelling approach - Supercharger 3.0 TFSI Results - Transient flow phenomena Summary 1

2 EASC 2009 Introduction CFD areas in engine development Cooling Car components Water jacket Components (Thermostat) Thermal management Air intake ducts, air filter Charge air ducts, intercooler Exhaust system Water / spray in inlet Oil duct Oil circuit Crank case Deep wading Cooling system ventilation Gas exchange Exhaust gas aftertreatment Intake / exhaust manifold design Catalyst O2 sensor Secondary air injection Gas dynamics Valve lift curves Boundary conditions for 3D CFD / FEA Combustion TFSI,TDI Engine-thermodynamics Intake manifold Exhaust manifold Intake / exhaust ports Charge motion flap 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 2

3 EASC 2009 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 3

4 Contents Introduction - Charging technology and CFD at Audi CFD modelling approach - Supercharger 3.0 TFSI Results - Transient flow phenomena Summary 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: Grey: Red / Blue lines: Boxes: Moving mesh domain Stationary domain Interface borders Intercoolers 4

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

5 CFD modelling approach Moving mesh domain Rotors are more or less cogwheelshaped 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 Rotors CFD modelling approach Moving mesh domain Dividing surface with 1:1 connection 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

6 CFD modelling approach Moving mesh domain CFD modelling approach CFD model setup Stationary boundary conditions at inlet and outlet Investigated operating points: 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 6

Contents Introduction - Charging technology

7 Contents 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 Results Air Inlet 56% 49% 44% 51% 50% 50% 50% 50% Inlet Outlet Inlet Outlet 7

8 Results Air inlet Blow holes connect all chambers in the suction part Contents 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 8

9 Results Pressure build up (full load) chamber pressure [bar] Chamber Pressure Inlet Area Chamber Volume Outlet Area Blow hole Upper blow holes connect chambers continuous pressure rise rotor angle [ ] relative volume / area [%] Results Pressure build up (full load) Static pressure 9

10 Contents 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 Results Outlet flow Part load: medium mass flow Strong axial flow direction forced upwards by left wall Zigzag flow 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

11 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 Contents 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 11

12 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 12

APPLICATION OF STAR-CCM+ TO TURBOCHARGER MODELING AT BORGWARNER TURBO SYSTEMS

APPLICATION OF STAR-CCM+ TO TURBOCHARGER MODELING AT BORGWARNER TURBO SYSTEMS BorgWarner: David Grabowska 9th November 2010 CD-adapco: Dean Palfreyman Bob Reynolds Introduction This presentation will focus