Engine Modeling with Modelica · Engine Modeling with Modelica November 19, 2002 Medium Models...
Transcript of Engine Modeling with Modelica · Engine Modeling with Modelica November 19, 2002 Medium Models...
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Engine Modeling with Modelica
Dr. John J. BattehFord Motor Company
Transient Engine Simulation GroupPowertrain Research Department
Modelica Automotive WorkshopEngine Modeling Session
November 19, 2002
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Engine Modeling with ModelicaNovember 19, 2002
Contributors� Eric Curtis (Group Leader, [email protected])� Michael Tiller ([email protected])
• Modelica technical lead� Charles Newman ([email protected])
• Engine and combustion modeling� John Batteh ([email protected])
• Heat transfer/thermal flow, liquid fuel effects� Chris Puchalsky (former group member)
• Liquid fuel effects � Allan Watson ([email protected])
• Hydraulics/thermal flow, lash adjuster� Kartik Ramanathan ([email protected])
• Manifold dynamics
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Engine Modeling with ModelicaNovember 19, 2002
Engine Physics
Engine analysis requires multi-domain physical models!!
Thermodynamics
Engine PerformanceMixture Properties
Combustion PredictionCompressible Flow
Heat Transfer
Metal-Gas InteractionsMetal-Fluid Interactions
Fluid Mechanics
Intake/Exhaust FlowIn-Cylinder Fluid Dynamics
Manifold DynamicsLiquid Fuel Effects
Coolant and Oil Flow
Mechanics
Valvetrain ActuationEngine MotionFriction Effects
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Engine Modeling with ModelicaNovember 19, 2002
Model Applications
� Engine-level analyses• Throttle response• Liquid fuel effects (wall
wetting)• Spark control response• Valve timing response• Manifold dynamics• Thermal warm-up
characterization
� Vehicle-level analyses• Drive cycle analyses
� Fuel economy� Emissions
• Vehicle control strategy development
• Energy management studies
• Powertrain analyses� Efficiency� NVH/shift quality
Wide array of applications necessitates flexibility!!
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Engine Modeling with ModelicaNovember 19, 2002
Model Characteristics
� Transient� Flexible
• Predictive vs. fixed combustion• Fidelity of component models
� Accuracy-speed tradeoff?• Working fluid calculations (medium models) • Fuel and air composition
� Configurable• Single vs. multi-cylinder
� Reusable• Same interfaces and similar basic components across
different analyses� User-friendly
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Engine Modeling with ModelicaNovember 19, 2002
Outline
� Introduction
� Interfaces
� Medium Model Concept
� Signal Bus Concept
� Sample Results
� Final Remarks
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Engine Modeling with ModelicaNovember 19, 2002
Interfaces
� Key to flexibility• Clearly define system interactions• Promote orthogonal model development• Provide framework for model compatibility
� Examples• Cylinder interface• Engine interface• Thermal architecture
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Engine Modeling with ModelicaNovember 19, 2002
Cylinder Interface
� Framework for all cylinder models• Partial model
� Defines external connections for cylinder
Induction System(Thermodynamic)
Exhaust System(Thermodynamic)
Crankshaft(1D rotational flange)
Engine block(1D rotational flange)
Camshaft(1D rotational flange)
Cylinder thermal environment(Thermal)
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Engine Modeling with ModelicaNovember 19, 2002
Engine Interface
� Framework for all engine models• Partial model
� Defines external connections for engine
� Extending models define plenum configuration• Single plenum• Dual plenum
Crankshaft(1D rotational flange)
Engine block(1D rotational flange)
Engine thermal environment(Thermal)
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Engine Modeling with ModelicaNovember 19, 2002
Complete Engine� Plug-n-Play with a variety of engine
configurations• Replaceable cylinder model fits in all engine
configurations
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Engine Modeling with ModelicaNovember 19, 2002
Thermal Architecture
� Provides framework for interaction between cycle simulation and engine temperature models• Cycle simulation models
� Responsible for metal-gas interactions• Transient engine temperature models
� Responsible for metal-fluid interactions� Allows orthogonal selection of models• Cycle simulation• Engine temperature
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Engine Modeling with ModelicaNovember 19, 2002
Cylinder Thermal Environment� “Connector of connectors”� Thermal bus � Comprised of connectors
for standard components which interact with various models• Thermal connectors for
various engine components (piston, block, head, etc.)
• Thermal connectors for engine fluids (oil, coolant)
• Friction connectors� Used with “break-out box”
in low level models
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Engine Modeling with ModelicaNovember 19, 2002
Engine Thermal Environment� Engine level connector
• Array of cylinder thermal environment connectors to allow for multiple cylinders
� Features• Parametric connector
representation for engines with multiple cylinders
• Consolidates signals to minimize connections� Single, engine-level
connection
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Engine Modeling with ModelicaNovember 19, 2002
Single-Cylinder Analysis
Using the Thermal Architecture
Engine Temperature Model
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Engine Modeling with ModelicaNovember 19, 2002
Challenges� Difficult to connect to
connectors within connectors• Direct connection not
possible• Requires termination of all
flow variables before connection (terminator model)� Signals requiring
termination grows exponentially with number of cylinders
� Resolving varying level of details in cycle simulation and engine temp. models
• Requires:� Averaging temperature� Dividing heat transfer
rate
Cycle Simulation Engine Temp.
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Engine Modeling with ModelicaNovember 19, 2002
Medium Models� Define specific working fluid� Consistent set of models,
functions, constants, connectors• Material properties (enthalpy,
energy, viscosity)• Equation of state• Chemical representation (# of
species)• Chemical kinetics of
combustion• Helper functions (air-fuel
ratio, etc.)� Implemented via replaceable
packages
� Features• Orthogonal development of
property models and the component models which use them
• Consistent framework for development of medium models with varying levels of detail
• Consistent application of changes throughout model hierarchy
• Organized� Information entirely contained
within medium model package
• Change working fluid at “flip of switch” at highest level
model EngineTestEngine engine(redeclare package MediumModel=Air)
end EngineTest;
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Engine Modeling with ModelicaNovember 19, 2002
Challenges
� More fool-proof specification of working fluid• Currently requires redeclaration of medium model in
each component • Single redeclaration that automatically propagates via
connections should be possible� Generic implementation?
• Applicable in all areas of modeling � Working fluids in hydraulics models� Fuel composition in wall wetting models� Material properties in heat transfer models
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Engine Modeling with ModelicaNovember 19, 2002
Engine Interface…Revisited
Crankshaft(1D rotational flange)
Engine block(1D rotational flange)
Engine thermal environment(Thermal)
Engine Interface
Connectors carryphysical signals
� How do we propagate control signals for modular hierarchies with replaceable components?• Redeclaring component
model may change information required� Generic cylinder� Cylinder with variable
cam timing• Impossible to anticipate
all types of signals that might be required by a specific implementation
• Not practical to propagate signals via connectors
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Engine Modeling with ModelicaNovember 19, 2002
Signal Bus� Signal bus idiom
• Facilitates propagation of control signals for replaceable component models
• Uses inner/outer semantics� Outer required to be subtype of inner
• Allows top-level definition for union of all control signals
• Allows selective definition/use of signals at low level
+Signal bus carries
control signals
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Engine Modeling with ModelicaNovember 19, 2002
Wall Wetting Model� Model details
• Multiple control volumes• Multi-component fuel• Evaporation• Fluid flow• Puddle shattering
(backflow)• Transient engine cycle
simulation• Transient engine
temperature model
� Applications• Throttle and speed
transients• Fuel composition studies• Injector targeting studies
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Engine Modeling with ModelicaNovember 19, 2002
Wall Wetting Results
0 2 0 4 0 6 0 8 0 1 0 03 6 0
3 7 0
3 8 0
3 9 0
4 0 0
4 1 0
4 2 0
4 3 0
Tim e [s ]
Tem
pera
ture
[K]
Va lv eCy lin d e rDo w n s tre a m P u d d leUp s tre a m P u d d leCo o la n t
0 20 40 60 80 1000
0.5
1
1.5
2
2.5
3 x 10-5
Tim e [s ]
Pud
dle
Mas
s [k
g]
Do w ns tre am PuddleUps tre am PuddleValv e PuddleCy linde r Puddle
0 20 40 60 80 10013
13.5
14
14.5
15
15.5
16
Tim e [s ]
Air
Fue
l Rat
io [-
]
A/F RatioInje c te d A/F Ratio
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Engine Modeling with ModelicaNovember 19, 2002
Wall Wetting Cycle Simulation
Mass flow ratepast valve [kg/s]
In-cylinder gastemperature [K]
Puddle masses [kg]
Mass fractions [-]
Valve
Downstream
Cylinder
Upstream
Burned Air
Unburned Air
Unburned Fuel
Burned Fuel
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Engine Modeling with ModelicaNovember 19, 2002
Final Remarks� Interfaces provide framework for extensible, flexible engine
models by independently choosing:• Combustion models• Transient engine temperature models• Medium models• Engine configurations
� Modelica language features highly suited to flexible modeling• Extends• Replaceable + Redeclare• Inner/outer semantics• Record semantics• Documentation and graphical annotations
� Looking ahead…• Challenges still exist
� Zero mass with intensive properties� Discussion and new ideas?