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Emissions Aftertreatment and Engine Cold-Starting Modeling. ORNL Investigators: Johney Green 1 , Stuart Daw 2 , Kalyan Chakravarthy 3 , Dean Edwards 3 , Zhiming Gao 3 , Jim Conklin 3 , Brian West 4 1 Program Manager, Vehicle Systems 2 Modeling Coordination 3 Modeling Team

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Emissions aftertreatment and engine cold starting modeling l.jpg

Emissions Aftertreatment and Engine Cold-Starting Modeling

ORNL Investigators:

Johney Green1, Stuart Daw2, Kalyan Chakravarthy3, Dean Edwards3, Zhiming Gao3, Jim Conklin3, Brian West4

1Program Manager, Vehicle Systems

2Modeling Coordination

3Modeling Team

4Engine and Vehicle Data

FY 2008 Vehicle Technologies Program Annual Merit Review, February 25-28, 2008

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Our objective is to generate PSAT maps and models for simulating emissions and fuel efficiency for advanced vehicle systems

  • Key approach elements:

  • Construct physically sound device models

  • Calibrate and validate models with experimental data

    • Vehicle and dynamometer measurements

    • Standardized laboratory characterization

    • Leveraging with other OVT projects (e.g., Advanced Combustion Research, CLEERS)

  • Implement models in Power System Analysis Toolkit (PSAT)

  • Study system behavior in PSAT simulations

    • Multiple powertrain configurations (plug-in hybrids are top priority)

    • Alternative fuels

    • Alternative control strategies

Fy2007 february 2008 accomplishments l.jpg

FY2007- February 2008 accomplishments

  • Generated Saab 2-L engine ethanol/gasoline maps and validated in PSAT with cold and hot start vehicle data

  • Added and validated external heat loss and thermal transients to PSAT models for engine and aftertreatment to account for impact on hybrid emissions and fueling

  • Transferred detailed LNT PSAT documentation to ANL (serves as template for future lean-exhaust aftertreatment components)

  • Began construction and validation of new PSAT 3-way catalyst model for stoichiometric PHEVs

  • Developed preliminary DPF and SCR diesel aftertreatment models

  • Demonstrated thermoelectric generator (TEG) model for exhaust heat recovery

  • Demonstrated PSAT capabilities to CLEERS Focus Groups and the DOE Diesel Cross Cut Team

We model engines by mapping engine and chassis dynamometer data l.jpg



Torque (ft-lb)



Engine Speed (rpm)








We 'model' engines by mapping engine and chassis dynamometer data

Detailed emissions, temperatures, & fuel rate measured for steady-state speed & load points

Surface maps interpolated in Matlab with defined speed-load limits

Such engine maps have been demonstrated to give good emissions simulations in psat l.jpg

Such engine maps have been demonstrated to give good emissions simulations in PSAT

PSAT engine out prediction

  • 21.8 mpg fuel economy

  • 4.5 NOx g/mi

  • 1.9 HC g/mi

  • 12.6 CO g/mi

  • 397 CO2 g/mi

Urban Dynamometer Driving Schedule (UDDS), std. CIVIC configuration, Saab 2.0-L engine map, gasoline fuel, cold start




  • 21.9 mpg fuel economy

  • 4.3 NOx g/mi

  • 2.1 HC g/mi

  • 12.0 CO g/mi

  • 380 CO2 g/mi

Engine maps are also corrected to simulate cold warm start transients l.jpg

Engine maps are also corrected to simulate cold/warm-start transients

UDDS, Civic configuration, Saab 2.0-L spark-ignition engine map, E85 fuel

Hot Start

Cold Start

  • Corrections based on global heat balance model

  • Accurate thermal transients needed to simulate catalyst light-off

  • Most emissions occur prior to and/or during catalyst light-off

Engine start stop is especially important for hybrid vehicle simulations l.jpg

Engine off at 60% state of charge (SOC)

Engine on at 54% state of charge (SOC)

Engine start/stop is especially important for hybrid vehicle simulations

UDDS, Parallel Hybrid CIVIC, Mercedes 1.7-L Engine Map

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Exhaust to tailpipe or subsequent device

Emission Control Device

Exhaust from engine or previous device

Aftertreatment models simulate component devices that reduce particulates, NOx, hydrocarbons, and CO


  • Globally correct physics and chemistry

  • Simplified kinetics and 1-D transient heat and species balances (ODEs)

  • Calibration with bench-scale and dynamometer data

    Key features:

  • Fast integration in Matlab/Simulink

  • Allow arbitrary input flow, temperature, species and hysteresis

  • Output temperature and flows for all tracked species

Engine and aftertreatment models are built to be configured as psat systems l.jpg

Request Speed/Load

Raw Exhaust

LNT Input

Emissions Out

Engine model

DPF/Oxy Cat models

LNT model

NOx sensor

Regeneration commanded?

Regeneration requested?

Engine supervisor

LNT supervisor

Regeneration parameters (e.g., magnitude, duration)

Engine and aftertreatment models are built to be configured as PSAT systems

The above schematic illustrates how diesel engines would be linked to aftertreatment. Key features include:

  • Multiple aftertreatment stages remove particulates and NOx

  • Sensors and controls supervise device-engine and device-device interaction

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Integrated system models allow PSAT to simulate the combined effects of engine type, hybrid configuration, and emissions control


  • Fuel economy: 50.8mpg

  • Engine-out NOx: 1.108g/ml

  • LNT-out NOx: 0.178g/ml

  • NOx reduction: 83.9%

  • LNT fuel penalty: 2.31%


  • UDDS, cold start

  • Mercedes 1.7-L diesel engine map

  • Conventional diesel fuel

  • Parallel hybrid Civic

  • Lean NOx Trap

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The preliminary thermo-electric generator (TEG) model for PSAT reveals important limitations

Model features

  • Single-pass cross-flow heat exchanger, glycol coolant

  • Commercial BiTe thermo-element

  • Constant physical properties (e.g., Z=0.0029 K–1)

    Example case

  • 1.7-L Mercedes diesel exhaust

  • US06 drive cycle

  • HX size 29  178  232 mm, 13.2 kg total, 2 kg thermo-element modules


  • HX effectiveness=57%

  • Max power output = 200 W

  • Net energy <20% of alternator

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Planned March-September FY 2008 Activities

  • Simulate emissions from various plug-in hybrid powertrains (e.g., gasoline, diesel, bio-fuel) including cold/warm-start effects and their impact on aftertreatment devices

  • Develop approach for simulating cold-start effects on engine-out and tailpipe emissions in PSAT

  • Improve PSAT 3-way catalyst model to account for engine transients in gasoline/ethanol fueled vehicles (Saab BioPower)

  • Continue validation of Mercedes CIDI engine map and LNT model PSAT predictions against experimental data

  • Complete construction, evaluation, and validation of DPF and urea-SCR models

  • Update PSAT oxidation catalyst model to include NO/NO2 output

  • Develop initial HC-SCR model

  • Construct initial “open” GM 1.9-L CIDI engine map (conventional and low temperature combustion)

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ORNL’s role emphasizes unique experimental facilities and modeling capabilities in the Fuels, Engines, and Emissions Research Center

  • Experimental vehicles

  • Engine dynamometer research cells

  • Materials and device characterization

    • Catalyst micro-structure and kinetics

    • Chemical and thermal materials properties

    • Laboratory bench reactors

    • Detailed dynamometer and vehicle measurements

  • Computational modeling

    • Systems models (e.g., PSAT, WAVE and GTPower)

    • CFD and chemistry models (e.g., KIVA, Chemkin)

    • Research device models in Fortran and MatLab

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Future Plans for Engine and Emissions Control Modeling

  • Incorporate new engine and emissions data and options into PSAT as they become available

    • Stoichiometric plug-in hybrid engines

    • 3-way catalysts with reduced noble metal requirements

    • Hybrid engines with lean HCCI and direct-injected combustion

    • Hybrid engines with PCCI in diesel combustion

    • DPF particulate control

    • Urea-SCR and HC-SCR NOx control

    • Hybrid engines with thermo-electric exhaust heat recovery

    • Hybrid engines with thermo-chemical recuperation

    • Compound expansion and combustion cycle hybrid engines

  • Continue utilizing data/models from other OVT activities

    • Advanced combustion engines R&D

    • Stretch efficiency

    • Thermo-electrics

    • CLEERS

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Additional Background on Oak Ridge National Laboratory (ORNL)and The Fuels, Engines, and Emissions Research Center (FEERC)

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High Temperature Materials Laboratory

National Transportation

Research Center

Oak Ridge National Laboratory

  • Began as part of the Manhattan Project

  • Nation’s largest multiprogram energy laboratory

  • World’s first nuclear reactor and now leading producer of medical radioisotopes

  • World’s most powerful microscope

  • Nation’s largest unclassified scientific computing facility

  • Nation’s largest science facility,the $1.4B Spallation Neutron Source

  • Nation’s largest concentration of open source materials research

Relevant Facilities

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Fuels, Engines, & Emissions Research Center…. a comprehensive laboratory for internal combustion engine technology

  • A DOE National User Facility in the NTRC

  • Focusing on alternative fuels, advanced combustion, and emission control R&D

  • Unique or extraordinary diagnostic and analytical tools for engine/emission control R&D

  • R&D from bench-scale to vehicle

    • Chemical/analytical labs

    • 9 dynamometer stands: 25-600 hp

    • Chassis dynamometer

    • Full-pass engine controls support research

    • Emissions analysis with high resolution of time and species

    • Non-invasive optical and mass-spec diagnostics

    • Modeling & simulation

Chassis dyno lab

Chassis Dyno Lab

Engine Cells


Offsite Projects

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Surface Spectroscopy

Catalyst Fundamentals

Laser Diagnostics Remote Sampling

Medium-Duty Diesel

Heavy-Duty Diesel

Light-Duty Diesel

Advanced Combustion, Fuels, Efficiency

Ethanol SI Efficiency

Delphi CRADA

Chassis Laboratory

Ethanol, Controls


HCCI, Fuels, Materials, Aftertreatment, Variable Compression

Analytical Chemistry

Bench Core Reactor,

Emissions & Particulate Characterization

Light-Duty Diesel

Emissions Control Integration

Heavy-Duty Diesel


Medium-Duty Diesel

Variable Valve Actuation, Emissions Control

Feerc staff comprise many disciplines also can tap other resources at ornl l.jpg

35 total staff, including post-doc, post-masters

ME, ChE, Chemistry, Physics, Env. Chemistry, Materials/Ceramics Engr, Engr. Mechanics

Student researchers, 3-5 at any time

Emissions characterization, both gaseous and particle

Non-linear dynamics and controls

Engine controls




Emission control modeling

Engine fundamentals and thermodynamics

FEERC Staff Comprise Many Disciplines, also can tap other resources at ORNL

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