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CAx in Automotive and Engine Technology
Assoc.Prof. Dr. Roland Kirchberger17th and 24th October 2016
Winter Term 2016/17
CAx in Automotive and Engine Technology 2
Fundamentals of CAx in Engine Design – Examples and Status
Very early history of CAx Geometry Process Engine Mechanics Functionality Development Engine Management and Calibration
Selected Examples of CAx in Engine Engineering
Content
CAx in Automotive and Engine Technology 3
About 200 years ago (1809) Ferdinand Redtenbacher, an Austrian engineer started with the „Science of mechanical engineering“ (Steyr, Upper Austria)Later, Carl Benz and Eugen Langen (friend of Nikolaus Otto), started with the optimization of steam engines, to improve the efficiency and the material usage.
Prototype = Series
Hence very high quality of design was mandatory
Stress analysis and thermodynamic analysis were of biggest concern in the beginning
Historic Motivation for Simulation – Large Engines
CAx in Automotive and Engine Technology 4
• 2D/3D Design Data• Type Range Family• Process Data• Engine DMU• Visualisation• Process Data
Management• Geometry Data
Management
Vehicle
Production
Engine
Type Range
Geometry Process
CAx in Automotive and Engine Technology 5
Valve Train
Belt Drive / Tensioner
Coolant Flow in Cyl. Head and Block
Engine Mountings
Heat Transfer andThermal Stresses
Piston and Cranktrain
Turbocharger
Exhaust System
Chain Drive
VibrationCrank Shaft / Damper
Crank Shaft, Bearings
VibrationAcoustics
Friction
CAx Application in the Development of Engine Mechanics
CAx in Automotive and Engine Technology 6
• Statics• Dynamics• Multi-body Systems• Thermo-mechanics• Fatigue• Acoustics, NVH• Process Simulation• Topology
Optimization
Source: Dr. Nefischer, Handbuch Verbrennungsmotorlow
high
Degree Crankangle [°CA]
Ben
ding
Mom
ent
Engine - Mechanics
CAx in Automotive and Engine Technology 7
Acoustics
Statics
Thermo-mechanics
Fatigue
Process Simulation
Multi-body systems
Dynamics
Topology optimization
StatusGoal
CAx Engine – Mechanics
CAx in Automotive and Engine Technology 8
Equivalent system single valve
valve spring
valve plate
valve shaft
tappet
cam
connecting geometry
radial bushing
shaftshaft with belt pulley
rotational excitation
belt pulley
TYCON – VALVE TRAIN
Example for Problem Orientated MBS
CAx in Automotive and Engine Technology 9
Valve Seat Force – Inlet Cam
Pressure Cam / Tappet
Acceleration of Inlet Valve
TYCON – Valve Train
CAx in Automotive and Engine Technology 10
Simplification of the 3D Model
Pressure distribution in the cylinder head gasket
Example for Application of a Static FEM
CAx in Automotive and Engine Technology 11
Mould Filling History after 6,8,10,12,14,16,18,20 sec
Example for Process Optimization for Aluminum Sand Casting
CAx in Automotive and Engine Technology 12
Local liquid fractionafter 87 sec
values<30% invisible
Local densityafter solidification
values>98% invisible
Temperature distributionafter 88 sec
Example for Process Optimization for Aluminum Sand Casting
CAx in Automotive and Engine Technology 13
Example for Acoustic Optimization of an Engine Crankcase
CAx in Automotive and Engine Technology 14
New light weight crankcase and capsule, to reduce the typical bell motion
Example for Acoustic Optimization of an Engine Crankcase
CAx in Automotive and Engine Technology 15
Gas Exchange
Calibration Parameter
Mixture Formation
Injection Hydraulics
Combustion
Emission Formation
Turbocharger
Catalytic Converter Behavior
Electr. System /Charging
LabCar / HIL
Oil System
EGR Distribution,Dynamics
Unfiltered / Filtered Air
CAx Application in Functionality Development of Engines
CAx in Automotive and Engine Technology 16
...
Heat flux/Ion-current sensors
Standard measurement
...
Combustion
Gas exchange
...
LDA
LIF
...
Combustion/Emissions
Mixture formation
Closed loopAnalysis/Synthesis
Engine conceptspecifications
Powertrain targets
1-cylinder engine
3D-Simulation
Optimized engineconcept
0D+1D-Simulation
optical engine
Combustion Development Process
CAx in Automotive and Engine Technology 17
Test BenchSingle Cylinder
Research Engine
p, TV p, TU
0D- Simulation
3D-CFD Simulation3D-CFD SimulationTest Bench Full Engine
HONNOH 22 HONNOH 22
OONNO 222 OONNO 222
NONOOON 2 NONOOON 2
HNONOH HNONOH ONONO 2 ONONO 2
NNOON 2 NNOON 2
Emission Formation Sim.
1D- Simulation
Process Functionality Development Engine
CAx in Automotive and Engine Technology 18
Status CFD-Simulation: Reproduction of fundamental mechanisms
inlet flow, charge motion,fuel injection, evaporation, combustion
Understanding of mixture formation and combustion Time intensive Direct numerical simulation not yet possible
Target CFD – Simulation (not entirely achieved yet):Prediction of Behavior
Increase of quality of predictionSelection of test configurationsSensitivity to small changes
Injection process, fuel – wall interaction Combustion, knocking, emission Formation, …
Mixture Formation and Combustion of DI Engines
CAx in Automotive and Engine Technology Source: Kemmler, Daimler Chrysler
Air-Fuel RatioMain Injection
Ingnition TimingVar. Length Inlet Pipe
Inlet Valve TimingOutlet Valve Timing
Charge Motion Device
Coolant Thermostat
Rail PressurePilot Injection
T1-Time
Delta Ignition TimingT2-Time
Post Injection
Total Injected MassNumber of Injections
External EGRBoost Pressure
Outlet Valve Lift
Inlet Valve Lift
Port Injection Direct Injection
Application Effort
Number of Variables
R4: Inline 4Cyl. V6: V-Engine ATL: Turbocharged
Otto Engine Concepts and Degrees of Freedom
CAx in Automotive and Engine Technology
Injection Timing early
Igni
tion
Tim
ing
e
arly
BSFCmin
Optimization of Operating Parameters at Stratified Part Load Operation
Parameter: Verification/Application
Ignition Timing 5
Start of Injection 4
Injection Pressure 4
Intake Manifold Pressure 4
EGR 4
Swirl 4
per Operating Point >5000 Meas. Pts.
Automated Test Bench Operation
with Interface Engine Management – Test Bench
Choice of Criteria (HC, COV, BSFC)
Automated Optimization following Main Criteria
Statistic Experiment Planning and Similar Prod.
CAx in Automotive and Engine Technology 21
Design of Experiments (DoE) for ApplicationThe key word DoE mostly refers to the following two topics:
Statistic Experiment Planning Original meaning of DoE Common speech: selective choice of measurement points from a
statistic point of view Target: maximum of information with acceptable accuracy about a
complex system with a minimum of measurement points.
Modelling of the system under consideration Equation systems (Cornerstone, RS1, Matlab/KFR) Neural networks (Nemo) Modeling of measurement errors Assessment of the modeling quality Verification by measurement of found optima
CAx in Automotive and Engine Technology 22
Fullpass
I / O-board
Bypass
ECU
Lab CarHiLHiL::- Ascet- Dspace
Validation-,Analysis-Test Beds/-ToolsFired SingleCylinder, Optical Engine, Flow Rigs/ Combustion Analysis
Conception
Digital Mock-UpCAD:CAD:-Def .-Spec .-Design
Engi
neH
ardw
are
ApplicationCAM:CAM:- Casting model- Machining
CAE:CAE:- Assy sim.- FEM- Dynamics- VR- CFD, Gas Exchange
Analysis/Simulation
RapidRapidPrototypingPrototyping
VirtualVirtualPrototypingPrototyping
CASE:CASE:- Idea, Definition- Spec., Modelling
Engi
neFu
nctio
ns
Virtual Engine
Engine/Gear BoxModel
(VehicleModel)Con
trolle
r
Function Mock-Up
SiLSiL::- ATMOS, Promo,...- Matlab/Simulink, ...
Virtual Engine
Engine/Gear BoxModel
(VehicleModel)
Con
trolle
r
Function Simulation
Analogy Engine Hardware – ECU-Functionality Development
CAx in Automotive and Engine Technology 23
mzu mabp,V,T
+
Empirical Models (e.g. engine maps)+ simple form of modeling- exponential increase of application effort
Modeling of the Physics of the Processes+ analytical description of the process
dependable and accurate- complex modeling (expert know-how is
required)
Problem: High effort for complex processes !!!
Engine Management and Functionality Development
CAx in Automotive and Engine Technology 24
Virtual Engine remains (in the foreseeable future)a vision !
Geometry Process: CAx is common practice in development process
Engine Mechanics: CAx is standard and applied extensively, up to very complex and coupled models of stat./dyn., thermo-mechanical and acoustic processes.
Functionality Development: Modeling of combustion process and engine concepts with various 0-, 1- and 3-D procedures; Need for further development especially in field of combustion and emissions formation
Engine Management and Calibration: CAx gives the base for indispensable support for systems with numerous degrees of freedom (e.g. DI Otto, CR-Diesel) and for the development and test bench operation
Fundamentals of CAx in Engine Development - Summary
CAx in Automotive and Engine Technology 25
Development Phase
Com
plex
ity
Concept Phase Design Phase Prototype Phase
Empirical Know How & Simulations
Complex Simulations (3D CFD, FEM)
Test Bench, part / complete system simulations
Schematic of the Development Process for an Engine
CAx in Automotive and Engine Technology 26
Concept Phase Gas Exchange Simulation, Supercharging, Injection System, Combustion Process Simulation for efficiency-, WOT-, emission- assessment
of a concept, Software in the Loop, Thermal Management, Mechanics,...
Design Phase Design, Optics Engine Mechanics Dynamics, NVH
Prototype Phase, Test Bench Rapid Prototyping Simulation of System „Combustion Chamber“, Combustion Diagnostics (TCA,..) Engine Management, Application Complete System Analysis, HIL
Selected Examples
CAx in Automotive and Engine Technology 27
Simulation Methods: Fill- and Drain Method
Influence of gas dynamics (e.g. pressure pulse of ram effect or tuned intake pressure charging) cannot be incorporatedExample: Layout calculation of turbo charger
1D Gas Dynamics Standard application for layout of gas exchange system, commercially available software (Boost, Promo, Wave,..)
3D Gas DynamicsTo some extend applied for assessment of losses, for local „peculiarities“ as extension of the 1D simulation
Simulation of the Gas Exchange
CAx in Automotive and Engine Technology 28
Potential concerning efficiency
8 10 12 14 16 18 20Compression ratio [-]
30
32
34
36
38
40
42
44
50
Indi
cate
d ef
ficie
ncy i
HP
[%] 46
48
n=2.000 RPMIMEP=6 bar
Wall heatlosses
- 10%
+ 25%
- 35%
+ 10%
- 25%
CurrentConfig.
CAx in Automotive and Engine Technology 29
Abb 5.2 , Boost
Simulation of Gas Exchange Process
CAx in Automotive and Engine Technology 30
Source: Dr.Nefischer, BMW
low
highEGR concentration in lower chamber
EGR concentration in upper chamber
Optimizationbefore
after
Optimization of EGR - Distributionin the Intake Manifold
CAx in Automotive and Engine Technology 31
Status Simulation: The working process of the ICE is too complex (up to now) to
be simulated in its entirety. (including the thermodynamic-, chemical-, flow dynamic processes in the comb. chamber, intake & exhaust System, turbo charging, EGR,..)
Very close combination with analysis of existing systems Various simplifications necessary to limit effort of modeling
and CPU time Goal Simulation: Prediction of behavior of new or altered systems Layout of new engine concepts, selection of models for
testing, reduction of number of expensive prototypes ...
Literature: Thermodynamik der VKM (Pischinger, Klell, Sams) , Springer-Verlag
Simulation of the System „Combustion Chamber“
CAx in Automotive and Engine Technology 32
Phenomenological Models: Phenomena are described with empirical or half empirical
functions of the relevant parameters, without direct math. incorporation of the physics laws of conservation
In general simple in set up and handling, in most cases each application requires
coefficients only available from experimentsExample: model of wall heat transfer in combustion
chamberPhysical Models: Based on mathematical formulations of fundamental laws of
physics (Conservation of mass, energy, momentum, …) Statistic models
Implemented Calculation Models for the Simulation of the System „Combustion Chamber“
CAx in Automotive and Engine Technology 33
For the description of the transient system „Combustion Chamber“ time and 3 positional coordinates have to be considered. (Required) simplifications: 0D Models (better: „time-dimensional“)
Consideration of time- but not position dependent parameters
Quasidimensional Approaches Consideration of local phenomena and geometrical characteristics within a 0D-model, applied in e.g. flow simulation, combustion, heat transfer
One- and multi dimensional ApproachesOne dimensional models are often used for the analysis of flow behavior of intake and exhaust systems
More complex flow fields require multi dimensional models (CFD – Computational Fluid Dynamics)
Implemented Calculation Models for the Simulation of the System „Combustion Chamber“
CAx in Automotive and Engine Technology 34
Three Dimensional ModelingProcesses in the ICE have Reynolds Numbers in the range of 105 to 107; Direct Numerical Simulation (DNS) is up to now impossible (complete description of position and time dependent flow field today possible up to order of magnitude Re < 103 )
Coarse Structure Simulation (Large Eddy Simulation LES)Selective simulation of important areas of a flow field or turbulence spectrum - mesh is adapted to turbulence structures
Statistical ApproachSplitting of the flow parameters into mean value and variation, use of turbulence models (e.g. kε model)
Multi Dimensional Approaches for the Simulation of the System „Combustion Chamber“
CAx in Automotive and Engine Technology 35
Examples of CFD SimulationPremixed Combustion in Large EnginesUse of CFD Simulation for the analysis of the flame propagation depending on different combustion types and for the optimization of geometry parameters
Structure with approximately 150.000 cellsCombustion and flame calculated with PDF-approach
(probability density function) Analysis of swirl effect
CAx in Automotive and Engine Technology 36
VerificationVerification
Flow, Mixture Formation
Application:
Combustion
Knocking
Model Development
347 °KW 352 °KW 357 °KW 362 °KW 367 °KW 372 °KW
347 °KW 352 °KW 357 °KW 362 °KW 367 °KW 372 °KW
Without swirl:
With swirl:
Influence of Swirl Motion on Combustion
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