Emissions Aftertreatment and Engine Cold-Starting Modeling

1. 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

2. 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

3. 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

4. 150 100 Torque (ft-lb) 50 0 Engine Speed (rpm) 0 1000 2000 3000 4000 5000 6000 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

5. 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 Overall Detail Experiment • 21.9 mpg fuel economy • 4.3 NOx g/mi • 2.1 HC g/mi • 12.0 CO g/mi • 380 CO2 g/mi

6. 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

7. 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

8. 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 Approach: • 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

9. 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

10. Integrated system models allow PSAT to simulate the combined effects of engine type, hybrid configuration, and emissions control Performance • 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% Parameters • UDDS, cold start • Mercedes 1.7-L diesel engine map • Conventional diesel fuel • Parallel hybrid Civic • Lean NOx Trap

11. 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 Results • HX effectiveness=57% • Max power output = 200 W • Net energy <20% of alternator

12. 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)

13. 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

14. 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

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

16. 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

17. 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 AnalyticalLabs Offsite Projects

18. 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 Single-Cylinder HCCI, Fuels, Materials, Aftertreatment, Variable Compression Analytical Chemistry Bench Core Reactor, Emissions & Particulate Characterization Light-Duty Diesel Emissions Control Integration Heavy-Duty Diesel DDC CRADA & WFO Medium-Duty Diesel Variable Valve Actuation, Emissions Control

19. 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 Combustion Catalysis Fuels Emission control modeling Engine fundamentals and thermodynamics FEERC Staff Comprise Many Disciplines, also can tap other resources at ORNL