CAx in Automotive and Engine Technology. Assoc.Prof. Dr. Roland Kirchberger 17 th and 24 th October 2016 Winter Term 2016/17

Transcription

1 CAx in Automotive and Engine Technology Assoc.Prof. Dr. Roland Kirchberger 17 th and 24 th October 2016 Winter Term 2016/17

2 Content 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 CAx in Automotive and Engine Technology 2

3 Historic Motivation for Simulation Large Engines 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 CAx in Automotive and Engine Technology 3

4 Geometry Process 2D/3D Design Data Type Range Family Process Data Engine DMU Visualisation Process Data Management Geometry Data Management Type Range Engine Vehicle Production CAx in Automotive and Engine Technology 4

5 CAx Application in the Development of Engine Mechanics Valve Train Coolant Flow in Cyl. Head and Block Heat Transfer and Thermal Stresses Piston and Cranktrain Turbocharger Exhaust System Vibration Acoustics Friction Belt Drive / Tensioner Chain Drive Crank Shaft, Bearings Vibration Crank Shaft / Damper Engine Mountings CAx in Automotive and Engine Technology 5

6 Engine - Mechanics Statics Dynamics Multi-body Systems Thermo-mechanics Fatigue Acoustics, NVH Process Simulation Topology Optimization high Bending Moment Degree Crankangle [ CA] low Source: Dr. Nefischer, Handbuch Verbrennungsmotor CAx in Automotive and Engine Technology 6

7 CAx Engine Mechanics Dynamics Status Goal Topology optimization Statics Multi-body systems Thermo-mechanics Acoustics Fatigue Process Simulation CAx in Automotive and Engine Technology 7

8 Example for Problem Orientated MBS shaft with belt pulley shaft radial bushing rotational excitation connecting geometry belt pulley cam Equivalent system single valve valve spring tappet valve shaft valve plate TYCON VALVE TRAIN CAx in Automotive and Engine Technology 8

9 TYCON Valve Train Valve Seat Force Inlet Cam Acceleration of Inlet Valve Pressure Cam / Tappet CAx in Automotive and Engine Technology 9

10 Example for Application of a Static FEM Pressure distribution in the cylinder head gasket Simplification of the 3D Model CAx in Automotive and Engine Technology 10

11 Example for Process Optimization for Aluminum Sand Casting Mould Filling History after 6,8,10,12,14,16,18,20 sec CAx in Automotive and Engine Technology 11

12 Example for Process Optimization for Aluminum Sand Casting Temperature distribution after 88 sec Local liquid fraction after 87 sec values<30% invisible Local density after solidification values>98% invisible CAx in Automotive and Engine Technology 12

13 Example for Acoustic Optimization of an Engine Crankcase CAx in Automotive and Engine Technology 13

14 Example for Acoustic Optimization of an Engine Crankcase New light weight crankcase and capsule, to reduce the typical bell motion CAx in Automotive and Engine Technology 14

15 CAx Application in Functionality Development of Engines Unfiltered / Filtered Air Gas Exchange Mixture Formation Injection Hydraulics EGR Distribution, Dynamics Combustion Emission Formation Turbocharger Calibration Parameter Electr. System / Charging LabCar / HIL Oil System Catalytic Converter Behavior CAx in Automotive and Engine Technology 15

16 Combustion Development Process Powertrain targets Engine concept specifications 1-cylinder engine Standard measurement 0D+1D-Simulation Gas exchange Heat flux/ion-current sensors... optical engine LIF Closed loop Analysis/ Synthesis Combustion... 3D-Simulation Mixture formation LDA Combustion/Emissions Optimized engine concept CAx in Automotive and Engine Technology 16

17 Process Functionality Development Engine Test Bench Single Cylinder Research Engine p, T V p, T U 0D- Simulation 1D- Simulation 3D-CFD Simulation N 2 O NO N O 2 N NO O OH N NO H N 2 O O NO NO O 2 N 2 N 2 O O OH N N O H 2 2 H Emission Formation Sim. Test Bench Full Engine CAx in Automotive and Engine Technology 17

18 Mixture Formation and Combustion of DI Engines 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 prediction Selection of test configurations Sensitivity to small changes Injection process, fuel wall interaction Combustion, knocking, emission Formation, CAx in Automotive and Engine Technology 18

19 Otto Engine Concepts and Degrees of Freedom Inlet Valve Lift Outlet Valve Lift Boost Pressure External EGR Number of Variables Number of Injections Total Injected Mass Post Injection T2-Time Delta Ignition Timing T1-Time Pilot Injection Rail Pressure Coolant Thermostat Charge Motion Device Outlet Valve Timing Inlet Valve Timing Var. Length Inlet Pipe Ingnition Timing Main Injection Air-Fuel Ratio Application Effort Port Injection Direct Injection R4: Inline 4Cyl. V6: V-Engine ATL: Turbocharged Source: Kemmler, Daimler Chrysler CAx in Automotive and Engine Technology

20 Optimization of Operating Parameters at Stratified Part Load Operation Parameter: Verification/Application Ignition Timing early Ignition Timing Start of Injection Injection Pressure Intake Manifold Pressure EGR Swirl per Operating Point >5000 Meas. Pts. BSFCmin 4 4 Automated Test Bench Operation with Interface Engine Management Test Bench Choice of Criteria (HC, COV, BSFC) Automated Optimization following Main Criteria Injection Timing early Statistic Experiment Planning and Similar Prod. CAx in Automotive and Engine Technology

21 Design of Experiments (DoE) for Application The 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 21

22 Analogy Engine Hardware ECU-Functionality Development Engine Hardware Engine Functions Conception CAD: -Def. -Spec. -Design CASE: -Idea, Definition - Spec., M odelling Digital Mock-Up Function M ock-up Controller Virtual Engine Engine/Gear Box Model (Vehicle Model) Analysis/Simulation CAE: - Assy sim. -FEM - Dynamics -VR -CFD, Gas Exchange Virtual Prototyping SiL: - ATMOS, Promo,... - Matlab/Simulink,... Function Simulation Controller Virtual Engine Engine/Gear Box Model (Vehicle Model) Application CAM: -Casting model - M achining Rapid Prototyping HiL: -Ascet -Dspace Lab Car Fullpass I / O-board Bypass ECU Validation-,Analysis-Test Beds/-Tools Fired Single Cylinder, Optical Engine, Flow Rigs/ Combustion Analysis CAx in Automotive and Engine Technology 22

23 Engine Management and Functionality Development Empirical Models (e.g. engine maps) + simple form of modeling - exponential increase of application effort m zu + p,v, T m ab 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!!! CAx in Automotive and Engine Technology 23

24 Fundamentals of CAx in Engine Development - Summary 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 CAx in Automotive and Engine Technology 24

25 Schematic of the Development Process for an Engine Concept Phase Design Phase Prototype Phase Complexity Complex Simulations (3D CFD, FEM) Test Bench, part / complete system simulations Empirical Know How & Simulations Development Phase CAx in Automotive and Engine Technology 25

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 Selected Examples Rapid Prototyping Simulation of System Combustion Chamber, Combustion Diagnostics (TCA,..) Engine Management, Application Complete System Analysis, HIL CAx in Automotive and Engine Technology 26

27 Simulation of the Gas Exchange Simulation Methods: Fill- and Drain Method Influence of gas dynamics (e.g. pressure pulse of ram effect or tuned intake pressure charging) cannot be incorporated Example: Layout calculation of turbo charger 1D Gas Dynamics Standard application for layout of gas exchange system, commercially available software (Boost, Promo, Wave,..) 3D Gas Dynamics To some extend applied for assessment of losses, for local peculiarities as extension of the 1D simulation CAx in Automotive and Engine Technology 27

28 Indicated efficiency ihp [%] n=2.000 RPM IMEP=6 bar Potential concerning efficiency Compression ratio [-] Wall heat losses -35% -25% -10% Current Config. + 10% + 25% CAx in Automotive and Engine Technology 28

29 Simulation of Gas Exchange Process Abb 5.2, Boost CAx in Automotive and Engine Technology 29

30 Optimization of EGR - Distribution in the Intake Manifold EGR concentration in lower chamber EGR concentration in upper chamber high low before after Optimization Source: Dr.Nefischer, BMW CAx in Automotive and Engine Technology 30

31 Simulation of the System Combustion Chamber 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 CAx in Automotive and Engine Technology 31

32 Implemented Calculation Models for the Simulation of the System Combustion Chamber 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 experiments Example: model of wall heat transfer in combustion chamber Physical Models: Based on mathematical formulations of fundamental laws of physics (Conservation of mass, energy, momentum, ) Statistic models CAx in Automotive and Engine Technology 32

33 Implemented Calculation Models for the Simulation of the System Combustion Chamber 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 Approaches One 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) CAx in Automotive and Engine Technology 33

34 Multi Dimensional Approaches for the Simulation of the System Combustion Chamber Three Dimensional Modeling Processes in the ICE have Reynolds Numbers in the range of 10 5 to 10 7 ; 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 < 10 3 ) 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 Approach Splitting of the flow parameters into mean value and variation, use of turbulence models (e.g. kε model) CAx in Automotive and Engine Technology 34

35 Examples of CFD Simulation Premixed Combustion in Large Engines Use 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 cells Combustion and flame calculated with PDF-approach (probability density function) Analysis of swirl effect CAx in Automotive and Engine Technology 35

36 Influence of Swirl Motion on Combustion Application: Flow, Mixture Formation Combustion Without swirl: 347 KW 352 KW 357 KW 362 KW 367 KW 372 KW Knocking With swirl: Model Development 347 KW 352 KW 357 KW 362 KW 367 KW 372 KW Verification CAx in Automotive and Engine Technology 36