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Engine-Aftertreatment in Closed-Loop Modeling for Heavy Duty Truck Emissions Control

Oak Ridge National Laboratory-Zhiming Gao, Dean Deter, David Smith, Josh Pihl, C. Stuart Daw, James Parks
Published 2019-04-02 by SAE International in United States
An engine-aftertreatment computational model was developed to support in-loop performance simulations of tailpipe emissions and fuel consumption associated with a range of heavy-duty (HD) truck drive cycles. For purposes of this study, the engine-out exhaust dynamics were simulated with a combination of steady-state engine maps and dynamic correction factors that accounted for recent engine operating history. The engine correction factors were approximated as dynamic first-order lags associated with the thermal inertia of the major engine components and the rate at which engine-out exhaust temperature and composition vary as combustion heat is absorbed or lost to the surroundings. The aftertreatment model included catalytic monolith components for diesel exhaust oxidation, particulate filtration, and selective catalytic reduction of nitrogen oxides (NOx) with urea. Both the engine and aftertreatment models have been calibrated with dynamometer measurements from a commercial 2010-certificated 15-L Cummins diesel engine. The fuel consumption engine map with the reduced data is attached in the appendix. Simulations with the combined engine and aftertreatment models above appear to reveal important trends among the fuel efficiency, emissions control, power…
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Simulations of the Fuel Economy and Emissions of Hybrid Transit Buses over Planned Local Routes

SAE International Journal of Commercial Vehicles

Oak Ridge National Laboratory-Zhiming Gao, Tim J. LaClair, C. Stuart Daw, David E. Smith, Oscar Franzese
  • Journal Article
  • 2014-01-1562
Published 2014-04-01 by SAE International in United States
We present simulated fuel economy and emissions of city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but tailpipe (post-aftertreatment) emissions are affected by complex interactions between engine load and the transient catalyst temperatures, and the emissions results were found to depend significantly on motor size and details of each drive cycle.
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Comparative Urban Drive Cycle Simulations of Light-Duty Hybrid Vehicles with Gasoline or Diesel Engines and Emissions Controls

Oak Ridge National Laboratory-Zhiming Gao, C. Stuart Daw, David E. Smith
Published 2013-04-08 by SAE International in United States
We summarize results from comparative simulations of hybrid electric vehicles with either stoichiometric gasoline or diesel engines. Our simulations utilize previously published models of transient engine-out emissions and models of aftertreatment devices for both stoichiometric and lean exhaust. Fuel consumption and emissions were estimated for comparable gasoline and diesel light-duty hybrid electric vehicles operating over single and multiple urban drive cycles. Comparisons between the gasoline and diesel vehicle fuel consumptions and emissions were used to identify potential advantages and technical barriers for diesel hybrids.
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Simulated Fuel Economy and Emissions Performance during City and Interstate Driving for a Heavy-Duty Hybrid Truck

SAE International Journal of Commercial Vehicles

Oak Ridge National Laboratory-C. Stuart Daw, Zhiming Gao, David E. Smith, Tim J. Laclair, Josh A. Pihl, K. Dean Edwards
  • Journal Article
  • 2013-01-1033
Published 2013-04-08 by SAE International in United States
We compare the simulated fuel economy and emissions for both conventional and hybrid class 8 heavy-duty diesel trucks operating over multiple urban and highway driving cycles. Both light and heavy freight loads were considered, and all simulations included full aftertreatment for NOx and particulate emissions controls. The aftertreatment components included a diesel oxidation catalyst (DOC), urea-selective catalytic NOx reduction (SCR), and a catalyzed diesel particulate filter (DPF). Our simulated hybrid powertrain was configured with a pre-transmission parallel drive, with a single electric motor between the clutch and gearbox. A conventional heavy duty (HD) truck with equivalent diesel engine and aftertreatment was also simulated for comparison. Our results indicate that hybridization can significantly increase HD fuel economy and improve emissions control in city driving. However, there is less potential benefit for HD hybrid vehicles during highway driving. A major factor behind the reduced hybridization benefit for highway driving is that there are fewer opportunities to utilize regenerative braking. Our aftertreatment simulations indicate that opportunities for passive DPF regeneration are much greater for both hybrid and conventional…
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Simulation of Catalytic Oxidation and Selective Catalytic NOx Reduction in Lean-Exhaust Hybrid Vehicles

Oak Ridge National Laboratory-Zhiming Gao, C. Stuart Daw, V. Kalyana Chakravarthy
Published 2012-04-16 by SAE International in United States
We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel-powered hybrid and plug-in hybrid vehicles (HEVs and PHEVs). The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of commercially available Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust. Our results illustrate that the DOC-SCR combination can reduce CO, HC and NOx emissions without creating a significant direct fuel penalty, but there is also an increase in the possibility of ammonia slip. Also, the addition of an upstream DOC increases aftertreatment thermal inertia, delaying light-off of the SCR catalyst. We find that the emissions reduction efficiency of the DOC-SCR…
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Detailed Chemical Kinetic Modeling of Iso-octane SI-HCCI Transition

Lawrence Livermore National Laboratory-Mark Havstad, Salvador M. Aceves, Matthew McNenly, William Piggott
Oak Ridge National Laboratory-K. Dean Edwards, Robert Wagner, C. Stuart Daw, Charles E. A. Finney
Published 2010-04-12 by SAE International in United States
We describe a CHEMKIN-based multi-zone model that simulates the expected combustion variations in a single-cylinder engine fueled with iso-octane as the engine transitions from spark-ignited (SI) combustion to homogenous charge compression ignition (HCCI) combustion. The model includes a 63-species reaction mechanism and mass and energy balances for the cylinder and the exhaust flow. For this study we assumed that the SI-to-HCCI transition is implemented by means of increasing the internal exhaust gas recirculation (EGR) at constant engine speed. This transition scenario is consistent with that implemented in previously reported experimental measurements on an experimental engine equipped with variable valve actuation. We find that the model captures many of the important experimental trends, including stable SI combustion at low EGR (~0.10), a transition to highly unstable combustion at intermediate EGR, and finally stable HCCI combustion at very high EGR (~0.75). Remaining differences between the predicted and experimental instability patterns indicate that there is further room for model improvement.
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Neutron Imaging of Diesel Particulate Filters

Andrea Strzelec, Hassina Z. Bilheux, Charles E. A. Finney, C. Stuart Daw
Technische Universitaet Muenchen-Burkhard Schillinger, Michael Schulz
Published 2009-11-02 by SAE International in United States
This article presents nondestructive neutron computed tomography (nCT) measurements of Diesel Particulate Filters (DPFs) as a method to measure ash and soot loading in the filters. Uncatalyzed and unwashcoated 200cpsi cordierite DPFs exposed to 100% biodiesel (B100) exhaust and conventional ultra low sulfur 2007 certification diesel (ULSD) exhaust at one speed-load point (1500 rpm, 2.6 bar BMEP) are compared to a brand new (never exposed) filter. Precise structural information about the substrate as well as an attempt to quantify soot and ash loading in the channel of the DPF illustrates the potential strength of the neutron imaging technique.
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Nondestructive X-ray Inspection of Thermal Damage, Soot and Ash Distributions in Diesel Particulate Filters

3DX-Ray Ltd.-Jan A. Zandhuis
Oak Ridge National Laboratory-Charles E. A. Finney, Todd J. Toops, William P. Partridge, C. Stuart Daw
Published 2009-04-20 by SAE International in United States
We describe novel results of ongoing research at 3DX-RAY Ltd and Oak Ridge National Laboratory using new, commercially available, nondestructive x-ray techniques to make engineering measurements of diesel particulate filters (DPF). Nondestructive x-ray imaging and data-analysis techniques were developed to detect and visualize the small density changes corresponding to the addition of substances such as soot and ash to DPF monoliths. The usefulness of this technique was explored through the analysis of field-aged samples, accelerated-aged samples, and the synthetic addition of ash and soot to clean DPF samples. We demonstrate the ability to visualize and measure flaws in substrates and quantify the distribution of ash and soot within the DPF. We also show that the technology is sensitive enough for evaluations of soot and ash distribution and thermal damage without removing the DPF from its metal casing.
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Effects of Fuel Physical Properties on Diesel Engine Combustion using Diesel and Bio-diesel Fuels

SAE International Journal of Fuels and Lubricants

Oak Ridge National Laboratory-Joanna McFarlane, C. Stuart Daw
University of Wisconsin, Madison-Youngchul Ra, Rolf D. Reitz
  • Journal Article
  • 2008-01-1379
Published 2008-04-14 by SAE International in United States
A computational study using multi-dimensional CFD modeling was performed to investigate the effects of physical properties on diesel engine combustion characteristics with bio-diesel fuels. Properties of typical bio-diesel fuels that were either calculated or measured are used in the study and the simulation results are compared with those of conventional diesel fuels. The sensitivity of the computational results to individual physical properties is also investigated, and the results provide information about the desirable characteristics of the blended fuels. The properties considered in the study include liquid density, vapor pressure, surface tension, liquid viscosity, liquid thermal conductivity, liquid specific heat, latent heat, vapor specific heat, vapor diffusion coefficient, vapor viscosity and vapor thermal conductivity. The results show significant effects of the fuel physical properties on ignition delay and burning rates at various engine operating conditions. It is seen that there is no single physical property that dominates differences of ignition delay between diesel and bio-diesel fuels. However, among the 11 properties considered in the study, the simulation results were found to be most sensitive to the…
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Development and Validation of a Reduced Reaction Mechanism for Biodiesel-Fueled Engine Simulations

SAE International Journal of Fuels and Lubricants

Oak Ridge National Laboratory-Joanna McFarlane, C. Stuart Daw
University of Wisconsin, Madison-Jessica L. Brakora, Youngchul Ra, Rolf D. Reitz
  • Journal Article
  • 2008-01-1378
Published 2008-04-14 by SAE International in United States
In the present study a reduced chemical reaction mechanism for biodiesel surrogate fuel was developed and validated for multi-dimensional engine combustion simulations. An existing detailed methyl butanoate mechanism that contained 264 species and 1219 reactions was chosen to represent the oxygenated portion of the fuel. The reduction process included flux analysis, ignition sensitivity analysis, and optimization of reaction rate constants under constant volume conditions. The current reduced mechanism consists of 41 species and 150 reactions and gives predictions in excellent agreement with those of the comprehensive mechanism.In order to validate the mechanism under biodiesel-fueled engine conditions, it was combined with another skeletal mechanism for n-heptane oxidation. This combined reaction mechanism can be used to adjust the energy content of the fuel, and account for diesel/biodiesel blend engine simulations. The combined mechanism, ERC-bio, contains 53 species and 156 reactions. Biodiesel-fueled engine operation was successfully simulated using the ERC-bio mechanism.
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