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The Effect of EGR Dilution on the Heat Release Rates of Boosted Spark-Assisted Compression Ignition (SACI) Engines

Robert Bosch LLC-Jeff Sterniak
University of Delaware-Dennis Assanis
  • Technical Paper
  • 2020-01-1134
To be published on 2020-04-14 by SAE International in United States
This paper presents an experimental investigation of the impact of EGR dilution on the tradeoff between flame and end-gas autoignition heat release in a Spark-Assisted Compression Ignition (SACI) combustion engine. The mixture was maintained stoichiometric and fuel-to-charge equivalence ratio (ϕ') was controlled by varying the EGR dilution level at constant engine speed. Under all conditions investigated, end-gas autoignition timing was maintained constant by modulating the mixture temperature and spark timing. Experiments at constant intake pressure and spark timing showed that as ϕ' is increased, lower mixture temperatures are needed to match end-gas autoignition timing. Higher ϕ' mixtures exhibited faster initial flame burn rates, which were attributed to the higher estimated laminar flame speeds immediately after spark timing. At constant intake pressure and mass fraction burned at the onset of autoignition, end-gas autoignition rates increased significantly at higher ϕ' conditions. The increasing trends in peak autoignition rate and end-gas energy at autoignition onset were found to be consistent for all intake pressures ranging from 80 kPa to 150 kPa. For a constant spark timing, the mass…
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Evaluation of Low Mileage GPF Filtration and Regeneration as Influenced by Soot Morphology, Reactivity, and GPF Loading

FCA US LLC-Jordan Elizabeth Easter, Kiran Premchand
University of Michigan-Stanislav Bohac, John Hoard
Published 2019-04-02 by SAE International in United States
As European and Chinese tailpipe emission regulations for gasoline light-duty vehicles impose particulate number limits, automotive manufacturers have begun equipping some vehicles with a gasoline particulate filter (GPF). Increased understanding of how soot morphology, reactivity, and GPF loading affect GPF filtration and regeneration characteristics is necessary for advancing GPF performance. This study investigates the impacts of morphology, reactivity, and filter soot loading on GPF filtration and regeneration. Soot morphology and reactivity are varied through changes in fuel injection parameters, known to affect soot formation conditions. Changes in morphology and reactivity are confirmed through analysis using a transmission electron microscope (TEM) and a thermogravimetric analyzer (TGA) respectively.Evaluations regarding the impact of these varied soots on GPF performance is accomplished through monitoring of GPF filtration efficiency as a function of soot loading and monitoring of soot oxidation rates during GPF regeneration events. Size-dependent filtration efficiency across the GPF is determined with a Scanning Mobility Particle Sizer (SMPS). Soot oxidation during regeneration events is determined using a radio frequency (RF) sensor and periodic weighing of the GPF on…
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Benchmarking a 2018 Toyota Camry 2.5-Liter Atkinson Cycle Engine with Cooled-EGR

SAE International Journal of Advances and Current Practices in Mobility

Southwest Research Institute-Josh Alden
US Environmental Protection Agency-John Kargul, Mark Stuhldreher, Daniel Barba, Charles Schenk, Stanislav Bohac, Joseph McDonald, Paul Dekraker
  • Journal Article
  • 2019-01-0249
Published 2019-04-02 by SAE International in United States
As part of the U.S. Environmental Protection Agency’s (EPA’s) continuing assessment of advanced light-duty automotive technologies in support of regulatory and compliance programs, a 2018 Toyota Camry A25A-FKS 4-cylinder, 2.5-liter, naturally aspirated, Atkinson Cycle engine with cooled exhaust gas recirculation (cEGR) was benchmarked. The engine was tested on an engine dynamometer with and without its 8-speed automatic transmission, and with the engine wiring harness tethered to a complete vehicle parked outside of the test cell. Engine and transmission torque, fuel flow, key engine temperatures and pressures, onboard diagnostics (OBD) data, and Controller Area Network (CAN) bus data were recorded. This paper documents the test results under idle, low, medium, and high load engine operation. Motoring torque, wide open throttle (WOT) torque and fuel consumption are measured during transient operation using both EPA Tier 2 and Tier 3 test fuels. The design and performance of this 2018 2.5-liter engine is described and compared to Toyota’s published data and to EPA’s previous projections of the efficiency of an Atkinson Cycle engine with cEGR. The Brake Thermal Efficiency…
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Benchmarking a 2016 Honda Civic 1.5-Liter L15B7 Turbocharged Engine and Evaluating the Future Efficiency Potential of Turbocharged Engines

SAE International Journal of Engines

U.S. Environmental Protection Agency-Mark Stuhldreher, John Kargul, Daniel Barba, Joseph McDonald, Stanislav Bohac, Paul Dekraker, Andrew Moskalik
  • Journal Article
  • 2018-01-0319
Published 2018-04-03 by SAE International in United States
As part of the U.S. Environmental Protection Agency’s (EPA’s) continuing assessment of advanced light-duty (LD) automotive technologies to support the setting of appropriate national greenhouse gas (GHG) standards and to evaluate the impact of new technologies on in-use emissions, a 2016 Honda Civic with a 4-cylinder 1.5-liter L15B7 turbocharged engine and continuously variable transmission (CVT) was benchmarked. The test method involved installing the engine and its CVT in an engine-dynamometer test cell with the engine wiring harness tethered to its vehicle parked outside the test cell. Engine and transmission torque, fuel flow, key engine temperatures and pressures, and onboard diagnostics (OBD)/Controller Area Network (CAN) bus data were recorded.This article documents the test results for idle, low, medium, and high load engine operation, as well as motoring torque, wide-open throttle (WOT) torque, and fuel consumption during transient operation using both EPA Tier 2 and Tier 3 test fuels. Particular attention is given to characterizing enrichment control during high load engine operation. Results are used to create complete engine fuel consumption and efficiency maps and estimate CO2…
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Investigations of the Effect of Ambient Condition on SACI Combustion Range

Robert Bosch LLC-Brandon Mendrea, Yusuf Zeynel Abidin Akkus, Jeff Sterniak
Univ of Michigan-Yan Chang, Stanislav Bohac
Published 2015-04-14 by SAE International in United States
HCCI (Homogeneous Charge Compression Ignition) has the potential for significant fuel efficiency improvements and low engine-out emissions but a major limitation is its relatively small operating range, limited by pressure rise rate at high loads and cyclic variability and incomplete combustion at low loads. Spark Assisted Compression Ignition (SACI) can extend the operating range of HCCI, but since SACI includes both flame propagation and auto-ignition, it experiences higher cyclic variance than HCCI combustion and phasing control can be challenging. This paper investigates the effects of environmental conditions on SACI combustion.The first part of the paper investigates whether CA50 (the location of 50% heat release and the most commonly used combustion parameter for describing combustion phasing) is the best metric to describe combustion phasing and facilitate its control. CA50 and four other combustion phasing metrics are evaluated and compared in this study. To perform this evaluation, IMEP (Indicated Mean Effective Pressure) and RI (Ringing Intensity), key combustion outputs that are directly perceived by a driver, are plotted versus each combustion control parameter and the physical correlation…
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