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Aftertreatment Models in Full System Simulations for System Integration
Neal Currier Gary Salemme Lars Henrichsen
13th CLEERS Workshop 22 April 2010
Copyright Cummins Inc..
2
Overview
A/T models Analysis Lead Design Vehicle System Simulation Hardware in the Loop Develop Controls and Calibrations
3
Lean Exhaust Aftertreatment
Inherent chemical challenges are Broad range of conditions and applications
– Including off-road applications (marine, locomotive, mining, etc.)
Transient and unpredictable driving cycles Actively controlled devices On-board diagnostics
Mobile applications of such “chemical plants”, with high efficiency, durability and diagnostic transparency, require detailed, quantitative understanding of their chemistry, reaction engineering: • Models-assisted system/application design and controls (kinetics in the
“brains” of the trucks!)
4
A/T Catalyst Fundamentals
Collect performance data – Do performance and properties roughly fit the application? – New control strategy not new catalyst
Develop understanding of catalyst chemistry and kinetics – Precursor to control strategies – Physical limit maps
Collect data for model development
5
Active Catalytic Devices With a “Memory”
Catalyst Performance = F(T, P, [Ai], S.V., History) – Short-term History: e.g., trapping efficiency=f(amount trapped)
– Mid-term History: reversible morphological and chemical changes – Long-term History: catalyst “aging”
6
Overall Reaction Equations: NO + 1/2O2 <=> NO2 2NO2 + BaO +[O] <=> Ba(NO3)2
+4 +5 ?
LNT NOx Storage Process
NO2 adsorption includes both acid-base and redox chemistry [1] A
B
C
Kinetics, mass-transport and thermodynamics all play a role, depending on operation regime
TGA data
Rate
Capacity
Time, min
[1] Epling, Yezerets, Currier et al. “Overview of the Fundamental Reactions and Degradation Mechanisms of NOx Storage/ Reduction Catalysts”. Catalysis Reviews; V46(2004), p.163-245
7
Re-arrangements via “nitrate melting”
Original performance
After SO2 Poisoning
After NOx testing
Sulfated a “Degreened” LNT, – Lost ~1/3 of NOx capacity
300-400C NOx operation Subsequent Temperature-Programmed Reduction (TPR): no change
in [S] amount or nature
8
Sulfur poisoning
NOx capacity data-Sulfation
NOx cycle data-Sulfation NOx cycle data- partial deSulfation
9
Sulfur Removal vs. Thermal Deactivation
Minimize excessive temperature exposure – Accurate control of deSOx temperature – Minimize temperature gradients across the NAC – Optimize reductant quality – Target only relevant forms of sulfur – Capable laboratory diagnostic tools
Loading of removable sulfur
NO
x C
apac
ity
Thermal
aging
10
Model Validation – How good is good?
SCR Inlet NOx, NH3 SCR Outlet NOx, NH3
Space Velocity: 40 [k/hour]; Temperature: 200 [C]
NOx Split: 0.5
Dynamic SCR
11
From the components, an A/T System is Built
The level of model is appropriate to – the element modeled – the use of the model – The existing understanding of the component
12
What level of A/T Model Detail is needed?
Map-based Models – Adequate for less complex catalysts in some simple applications
Simple 0D Models – Where spatial effects are minimal – either because of simple cycles (SS) or
simple applications (heat generation) 1D Models
– Where temperatures and other gradients exist 1D by 1D Models
– Where catalyst is coating changes formulation with depth in the coating – Wall flow devices
2D Models – Where radial temperature gradients are significant
3D CFD – Where flow distributions or compositional gradients exist
13
Systems Performance Analysis Tools
Design Calculation
Spreadsheet
Embedded Models
System Simulation
2D CFD 1
Slower Faster 3D CFD
Execution Speed/Real Time
100 0.1 0.01 0.0001 0.001
Simulink
Catalytic
Flow CFD
More Detail Less Detail
Matlab
Engine Cycle Simulation
All models are wrong, some are useful – George Box
Engine CFD & Combustion 1D A/T
Simulation
14
FTP: Accuracy/Speed Trade-off
15
Systems Performance Analysis Roles
Platform Teams • Primary Analysis Resource • Provide Customer Input /
Feedback to SPA
System Analysis Group • Alternate Analysis
Resource (Non-Cummins or Cummins)
• Technology Development
Systems Performance Analysis • Modeling Technology
Selection/Development • Model Integration /
Development • Model Acquisition • Model Certification • Model and Parameters
Storage • Develop Best Practices • Primary Support and Training • Alternate Analysis Resource
Other Cummins Groups Research and Technology
CRTI KPIT
Software Development Group
• Non-TSFE Tool Development Resource
Commercial Software Supplier • Provide Core Tool for
Aftertreatment and Engine Modeling
• Primary Support and Training
Supplier/Partner Modeling Groups • Provide Models • Consulting • Provide Calibration Data
University / National Lab Interactions • Provide Chemical Kinetics for
Aftertreatment • Fundamental Modeling Techniques
Non - Cummins Resources
Catalyst Technology Group • Aftertreatment Expertise • Provide Calibration Data • Provide Material Properties
Automotive Customer Engineering
• Route and Vehicle Expertise • VMS Connection
Simulation Test and Tools • Bench Technology
Development • Bench Hardware
Lab Operations • Test Cell Technology
Development • Test Cell Support
Catalyst Elements • Catalyst Information • Supplier Data
CES
CFD • Model Validation • Common Fundamentals
16
Analysis Led Design Engine Development
Pure Simulation
• Aftertreatment Parameter Studies • Uncoupled Flow, Temperature, Emissions • Aftertreatment Controls • Steady State and Transient
• Engine Parameter Studies • Coupled Torque, Flow, Temperature, Emissions • Engine and Aftertreatment Controls Interactions • Steady State and Transient
• Vehicle Parameter Studies • Engine and Aftertreatment Controls Interactions • Drive Cycle Transients
17
Vehicle System Simulation Concept
– Easier Data Acquisition – Repeatable and Realistic
Testing – Off nominal and “out of
season” tests
– Automated Testing – Engine Controls
development and testing – Fuel Economy Studies – Transient Emissions Testing
Move truck testing to computers and test cells
18
Population Evaluation
Need a way to characterize the population of vehicles
DeSox Capability
% o
f Cus
tom
ers
Target Capability
Problem Area
19
DeSox Capability
% o
f C
usto
mer
s
Target
Plan to Evaluate Population
Customer Survey
“Duty Cycle Parameter”
DeS
Ox
Cap
abili
ty At Risk
Customers
20
Case for high repeatability evaluation
Field Population
Road Test
Choose Reference
Chassis Test
Engine in the Loop Test
Pure Simulation
Relative Comparisons Best Handled Here
Harder to Resolve Improvements
Easier to Resolve
Mod
el C
alib
ratio
n
21
Dynamic System Overview
Plant
Controls
Environment
System
Operator
22
Time or Distance
Vehi
cle
Spee
d
Time
Time Th
rottl
e En
gine
Sp
eed/
To
rque
Regulatory Cycles - FTP75 - NEDC Actual Drive Cycles
Transmission Axle
Wheel
Driver
Clutch/Torque Converter
Route
Roa
d El
evat
ion
Vehicle Frame
Time Resolved Engine Performance
Vehicle System Performance Simulation
Vehicle Model
23
Signal Flows in Vehicle Simulation
Force
Speed
Actual Vehicle Speed
Vehicle** Drivetrain* Torque
Rotational Speed
Engine
Operator
Throttle Position
Speed Target
Time (or Position)
Driving Cycle (e.g., FTP75, NEDC)
Road Grade
[*] www.coastlinetrans.com
[**] www.leylandtrucksltd.co.uk
Clutch Position
Brake Position
Gear Number
24
But CyberApps is more than just vehicle
simulation
CyberApps© Sim Sim + Hardware
25
Route/Drive Cycle
Vehicle
Hybrid Components
Aftertreatment
Engine
ECM
Vehicle on Road
Vehicle in Loop
Pure Sim
Engine in Loop
AT in Loop
HPS in Loop
ECM in Loop
$ $ $ $
Systems Performance Simulation
26
PureSimulationApplication
Driveline Vehicle Engine
Engine Controls
Driver Drive Cycle Throttle Target Speed
Driveline Control
Engine Control Commands
Engine Sensor Signals
Torque
Speed
Torque
Speed
Environment Conditions
Vehicle Position
27
CyberAftTestApplication
Aftertreatment System
Aftertreatment Controls
Control Commands
Sensor Signals
Aftertreatment System Bench Test
Configurable Catalyst Elements
• Automated Tests • Steady State Tests • Transient Tests
Engine Output Conditions
User Defined Inlet Conditions • Flow • Temperature • Composition
Pure Simulation Only
28
ControllerintheLoop(CIL)ApplicationSimulation
Driveline Vehicle Engine
Engine Controls
Driver Drive Cycle Throttle Target Speed
Driveline Control
Engine Control Commands
Engine Sensor Signals
Torque
Speed
Torque
Speed
Environment Conditions
Vehicle Position
29
CyberBench Example - Computers
Computer Rack
Linux Computer Monitor/Keyboard/Mouse
Windows Computer Monitor/Keyboard/Mouse
ECM
30
EngineintheLoop(EIL)ApplicationSimulation
Driveline Vehicle
Driver Drive Cycle Throttle Target Speed
Driveline Control
Torque
Speed
Torque
Speed
Environment Conditions
Vehicle Position
31
Analysis Led Design Engine Development
Hardware In the Loop
• Engine Parameter Studies • Coupled Torque, Flow, Temperature, Emissions • Real Engine and Aftertreatment Controls Interactions • Steady State and Transient
• Vehicle Parameter Studies • Real Engine and Aftertreatment Controls Interactions • Real Engine Performance and Emissions • Drive Cycle Transients • Vehicle speed based regulatory cycles
32
Inlet Temperature
Flow Rate Composition
Single Channel Model 1D Axially Resolved
DPF
Catalyst
Calculations at Each Element at Each Time Step Flow Rate Pressure Drop Species Mass Transfer Chemical Reaction Rates Air to Substrate Heat Transfer Substrate Axial Heat Transfer Substrate Temperature Soot Collection (DPF) Soot Oxidation (DPF)
Outlet Temperature
Flow Rate Composition
Soot Layer
Aftertreatment System Simulation
Engine Cycle/System Simulation
Integrated Engine/Aftertreatment/Vehicle System Simulation
33
Component Models Component Features
Operator Input: Target vehicle speed. PIF controller with adaptive gains Outputs: Operator throttle and brake command (automatic), throttle, brake, clutch position, gear number (manual). Manual operator has a sophisticated shifting model. Target accel and decel rates can be changed to study variability
Routes Time based / position based. Grade input. Stop / idle time vs. time / position. VehMass vs. time / position.
Engine – Map Based Inputs: Throttle, speed and switch. Output: Torque Allows input of fuel map collected from test cell. Allows to perform quick engine sizing exercise.
Engine – Reduced GTPower
Mean Value Cylinder Simplified air handling subsystems Trends with air handling and fuel system commands
34
Component Features
Aftertreatment - Simple Map based models for real time Thermal response
Aftertreatment – 1 D Axially resolved single channel models Global kinetics of reactions Thermal response
Engine/Aftertreatment Controls - Simple
Simple map based controls for engine and aftertreatment commands
Engine/Aftertreatment Controls – Detailed (COMET)
Parts of actual production code running in simulation Import of actual calibration
Torque Converter Map based model; Maps of Torque ratio vs. speed ratio and K factor vs. speed ratio
Component Models
35
Component Models Component Features
Transmission Allows input of gear ratios Automatic Shift schedule map as a function of throttle angle and trans out speed. Gear loss: polynomial equation for speed based and a constant torque based for each mesh. Manual Gear loss: polynomial equation for speed based and a constant torque based for each mesh.
Axle Efficiency model similar to transmission Wheel Allows input of wheel size.
Wheel rolling loss model is a function of vehicle speed and mass Calculates brake force
Vehicle Allows input of Cd, vehicle height and width Allows input of A, B, C coefficients Calculates aerodynamic drag, grade force and vehicle acceleration (F=ma)
36
Example Simulation Capability
What is sensitivity of aftertreatment performance to drive route, engine calibration change, and regeneration temperature?
Application
Calibration
Significant Interactions
Identified with System Model
System Model
Peak Oxidation Catalyst Outlet Hydrocarbons (ppm)
37
Aftertreatment Controls Development Using Models
Aftertreatment Only Simulation
Increasing Storage Time
Time
NO
x N
Ox
In
Mas
s Flo
w
NH3 Storage Time (s)
High Temperature
Low Temperature
Time (s) Pe
ak N
Ox
Out
(Nor
mal
ized
)
38
Aftertreatment Controls Development Using Models
Engine Test Cell Simulation
Increasing Transient Response
NO
x
Time
Time (s)
Thro
ttle
(%)
Spee
d (r
pm)
Transient Torque (Normalized)
Peak
NO
x O
ut (N
orm
aliz
ed)
High Speed
Low Speed
39
Aftertreatment Controls Development Using Models
Vehicle Simulation
Vehi
cle
Spee
d (m
ph)
Cum
ulat
ive
NO
x (N
orm
aliz
ed)
Increasing Vehicle Mass
Time (s) Vehicle Mass (10,000 lb)
40
Simulation of deSOx Opportunities
LNTs require periodic regeneration to remove sulfur
Using engine managed measures, deSOx can only happen in limited areas of the engine operating map
Run vehicle simulations over various duty cycles to determine deSOx opportunities
41
Time at Temperature
42
What if?
We can now visualize where on the engine map adequate opportunities exist for desulfation
43
Urban Cycle
Detailed Evaluation
44
Summary
Vehicle simulation is an important part of the development of engine systems
Combinations of simulation and hardware are a critical part of that process – Controls – Engine – Vehicle
Model sophistication required may vary depending on the intent of the simulation and the available simulation resources
Vehicle simulations are not the only uses of A/T models