Impact of Miller Cycle Strategies on Combustion Characteristics, Emissions and Efficiency in Heavy-Duty Diesel Engines

Journal Article · Tue Apr 14 00:00:00 EDT 2020 · SAE Technical Paper Series

DOI:https://doi.org/10.4271/2020-01-1127· OSTI ID:2000843

Garcia, Erick ^[1]; Triantopoulos, Vassilis ^[2]; Boehman, Andre ^[2]; Taylor, Maxwell ^[3]; Li, Jian ^[3]

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1. University of Michigan, Ann Arbor, MI (United States); University of Michigan
2. University of Michigan, Ann Arbor, MI (United States)
3. Volvo Trucks North America, Hagerstown, MD (United States)

This study experimentally investigated the potential of Miller cycle strategies as a means to improve fuel consumption and reduce NO_x emissions in heavy-duty diesel engines. The experiments were conducted at constant engine speed, load, and engine-out NO_x (1160 rev/min, 1.76 MPa net IMEP, 4.5 g/kWh) on a single cylinder research engine equipped with a fully-flexible hydraulic valve train system. Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC) timing strategies were compared to a conventional intake valve profile. While the decrease in effective compression ratio associated with the use of Miller valve profiles was symmetric around bottom dead center, the decrease in volumetric efficiency (VE) was not. EIVC profiles were more effective at reducing VE than LIVC profiles. Despite this difference, EIVC and LIVC profiles with comparable VE decrease resulted in similar changes in combustion and emissions characteristics. Miller cycle operation at constant intake pressure resulted in lower peak cylinder pressure, higher exhaust temperatures and lower EGR requirements compared to the baseline case, albeit with a significant fuel consumption penalty. Increasing intake manifold pressure to match the baseline air-fuel ratio overcame the fuel consumption penalty, without compromising NO_x emissions. Selected EIVC/LIVC profiles were compared to the baseline condition at three different overall turbocharger efficiencies (n_TC). At the baseline n_TC, Miller cycle profiles can lower peak cylinder pressures and increase exhaust temperatures with a minimal penalty in BSFC and FSN. At higher n_TC than baseline, Miller cycle can maintain the benefits of lower peak cylinder pressure and higher exhaust temperature without a BSFC or FSN penalty.

• Research Organization: Volvo Technology of America, Inc., Washington, DC (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO)
• Contributing Organization: Delphi Automotive; ExxonMobil Research and Engineering
• Grant/Contract Number: EE0007745
• OSTI ID: 2000843
• Journal Information: SAE Technical Paper Series, Journal Name: SAE Technical Paper Series Vol. 2020; ISSN 0148-7191
• Publisher: SAE International
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
33 ADVANCED PROPULSION SYSTEMS
42 ENGINEERING
Heavy-duty
LIVC
Miller cycle
compression ignition
turbocharger efficiency