System Level Cooling, Fatigue, and Durability

System Level Cooling, Fatigue, and Durability
System Level Cooling,
Fatigue, and Durability
Analysis via Multiphysics
Co-Simulation
Stuart A. Walker, Ph.D.
[email protected]
Outline
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Motivation
Presentation of process
Presentation of tools
Presentation of the results
2
Importance of External Automotive
Aerodynamics via CFD
Visibility
• Dirt (soiling)
• Splash/spray
• Wiper lift off
Comfort
• Ventilation
• Heating
• Air conditioning
• Wind noise
downforce
Aero acoustics (CAA)
Stability
• Directional
• Cross wind sensitivity
Cooling
• Engine
• Transmission
• Brakes
• Condenser
Performance
• Fuel economy
• Emission
• Max. speed
• Acceleration
Spoiler oscillation, FSI
dragforce
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Importance of System Level Modeling
• Many important component level
responses
– Temperature
– Stress
– Displacement
• Component responses are coupled
via external aerodynamics,
structural physics, and control
systems
– Rotor example
Rotor/Brake Pad Friction
(hot side boundary conditions)
External Aerodynamics
(cold side boundary conditions)
Heat Transfer Simulation to
calculate rotor temperatures
AcuSolve Coupled Model
Thermo-structural Model
(durability and fatigue)
4
Outline
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Motivation
Presentation of process
Presentation of tools
Presentation of the results
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Engine Block Cooling Example
• Desired result:
– Temperature in engine block
– Stress in engine block
– Displacement in engine block
• Important CFD physics
– Underhood flow for HTC on engine block
– Water jacket flow for engine block cooling
• Modeling approach
– Compute HTC from external aero calc
– Compute temperature in solid from internal water jacket model
– Compute stress/displacement in solid
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General Approach
Thermo-structural Model
Combustion Simulation
(hot side boundary conditions)
Subcase 1:
• Bolt Pretension in Head Bolts
Heat Transfer Simulation to calculate
Engine Temperature loading
Subcase 2:
• Lock Pre-tension Displacements
• Apply Temperature Loading
External Aerodynamic Simulation
(cold side boundary conditions)
AcuSolve Coupled Model
Subcase 3:
• Lock Pre-tension Displacements
• Continue Temperature Loading
• Apply Combustion Pressure Loading
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External Aero Modeling
• External aerodynamics drive component level cooling
– Engine block cooled by underhood flow
– Radiator cooled by underhood flow
– Brake rotors cooled by flow through the wheel well
• Underbody Thermal Management
– Fluid flow
– Energy Transport
– Porous media
• Analysis
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Fluid and solid
Velocity and pressure
Temperature
Drag/lift
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Component Level Modeling
Component designs
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Exhaust systems
Radiator
Blower/Fans
Water jacket HX
Detailed analysis
– Fluid and solid
– Velocity and Pressure
– Temperature
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System Level Modeling
• Thermal management
– External aerodynamics
– Component level modeling
• Coupling for stress analysis
– AcuSolve
– Radioss
Friction / Motor Dissipation / Combustion
(hot side boundary conditions)
External Aero/HX Simulation
(cold side boundary conditions)
Heat Transfer Simulation to
calculate Engine Loading
AcuSolve Coupled Model
Thermo-structural Model
(durability and fatigue)
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Thermo-Structural Model
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Outline
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•
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•
Motivation
Presentation of process
Presentation of tools
Presentation of the results
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Modeling and Visualization Tools
• “One team – One solution”
• Altair Engineering, Inc.
– HyperWorks Suite provides an integrated
environment for pre/solve/post for system
level vehicle coupling of FEA, CFD, MBD, and
NVH physics
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Pre-Processing
• AcuConsole
– Dedicated pre-processor for AcuSolve
– Fast and robust CFD meshing (e.g. 90Mio tetras external automotive
80min)
• HyperMesh
– Solver neutral CFD grid generator
– Powerful geometry cleanup/generation tools
– One pre-processor for structural and CFD analysis
HyperMesh
AcuConsole
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Solver
• Radioss CFD/FSI
– Explicit multi-physics solver
– Coupled solver (structure + fluid)
– Suited for compressible flow
• AcuSolve
– Implicit multi-purpose CFD solver
– Finite element based
– Strong FSI capabilities (P-FSI, DC-FSI)
AcuSolve
Courtesy of HTT
Radioss
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AcuSolve
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General
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General purpose, 3-dimensional, unstructured CFD solver
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Based on Finite Element method (Galerkin Least Square, GLS)
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Originated at Stanford University by Prof. T.J.R. Hughes et. al. and further improved for industrial applications
Incompressible, weakly compressible Navier Stokes solver
Numerics
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2nd order accuracy (space and time) for all flow variables
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Scalable (e.g. customer runs on 1024 CPUs, 350Mio cells)
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Various turbulence models available (RANS, LES, DES)
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Transient / steady state
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Solving the fully coupled system
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Sliding mesh (rotating machinery)
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Moving/deforming mesh, ALE (Fluid-Structure)
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Post-processing
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AcuFieldView
– Dedicated CFD post-processor (OEM version of FieldView, Intelligent Light)
– Supports only AcuSolve results
– Client-server architecture, 8 way parallel
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HyperView
– Solver neutral CFD post-processor
– Showing structural and CFD results
in one framework
pressure
Top. Optim.
streamlines
eigenmodes
HyperView
AcuFieldView
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CFD Optimization with HyperWorks
Initial design
Cw = 1
UI = 0.83
Morphing
Optimization
Optimized design
Cw = 0.04
UI = 0.94
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Component Level Optimization
Success Story (CFD optimization)
Case: Exhaust system, catalytic converter
Objective: uniform flow, min. pressure drop
Result: uniformity +12%, pressure drop -16%
Case: Engine compressor, impeller blade
Objective: maximize pressure ratio
Result: pressure ratio +5.6%,
Case: Evaporator, HVAC system
Objective: uniform flow, min. pressure drop
Result: uniformity +5.6%, pressure drop -7%
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Outline
•
•
•
•
Motivation
Presentation of process
Presentation of tools
Presentation of the results
20
External Aero Solution
• Closed shell mesh generated in HyperMesh
– Shell mesh boolean
– CFD wrapping
• Starting point for “The Virtual Wind Tunnel”
– Ease of use
– AcuSolve behind the scenes
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External Aero Solution
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External Aero Results
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Engine Block Loading
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Static FEA Analysis in OptiStruct
Thermo-structural Model
Subcase 1:
• Bolt Pretension in Head Bolts
Subcase 2:
• Lock Pre-tension Displacements
• Apply Temperature Loading
Subcase 3:
• Lock Pre-tension Displacements
• Continue Temperature Loading
• Apply Combustion Pressure Loading
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Temperature Results
Cylinder Head
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Displacement Results
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Stress Results
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Contact Pressure and Bore Deformation
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Conclusion
• Altair HyperWorks Suite provides a
complete vehicle simulation package
– Pre-processing
• HyperMesh/AcuConsole
• Virtual Wind Tunnel
– Solver
• AcuSolve – CFD
• OptiStruct/Radioss – FEA
– Post-Processing
• HyperView/AcuFieldView
– CFD/FEA Optimization
• HyperMorph/HyperStudy
Stuart Walker, Ph.D. | CFD Specialist
[email protected] | altair.com
Altair | Innovation Intelligence®
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