Aftertreatment Models in Full System Simulations for System Integration

Neal Currier Gary Salemme Lars Henrichsen

13th CLEERS Workshop 22 April 2010

Copyright Cummins Inc..

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Overview

 A/T models  Analysis Lead Design  Vehicle System Simulation  Hardware in the Loop  Develop Controls and Calibrations

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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!)

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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

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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”

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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

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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

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Sulfur poisoning

NOx capacity data-Sulfation

NOx cycle data-Sulfation NOx cycle data- partial deSulfation

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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

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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

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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

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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

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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

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FTP: Accuracy/Speed Trade-off

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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

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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

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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

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Population Evaluation

Need a way to characterize the population of vehicles

DeSox Capability

% o

f Cus

tom

ers

Target Capability

Problem Area

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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

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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

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Dynamic System Overview

Plant

Controls

Environment

System

Operator

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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

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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

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But CyberApps is more than just vehicle

simulation

CyberApps© Sim Sim + Hardware

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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

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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

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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

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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

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CyberBench Example - Computers

Computer Rack

Linux Computer Monitor/Keyboard/Mouse

Windows Computer Monitor/Keyboard/Mouse

ECM

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EngineintheLoop(EIL)ApplicationSimulation

Driveline Vehicle

Driver Drive Cycle Throttle Target Speed

Driveline Control

Torque

Speed

Torque

Speed

Environment Conditions

Vehicle Position

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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

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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

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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

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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

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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)

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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)

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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

)

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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

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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)

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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

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Time at Temperature

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What if?

  We can now visualize where on the engine map adequate opportunities exist for desulfation

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Urban Cycle

Detailed Evaluation

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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