Extreme Miller cycle with high intake boost for improved efficiency and emissions in heavy-duty diesel engines

Journal Article · Mon Dec 06 00:00:00 EST 2021 · International Journal of Engine Research

DOI:https://doi.org/10.1177/14680874211059309· OSTI ID:2000842

Garcia, Erick ^[1]; Triantopoulos, Vassilis ^[2]; Trzaska, Joseph ^[2]; Taylor, Maxwell ^[3]; Li, Jian ^[3]; Boehman, André L. ^[2]

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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 investigates the impact of extreme Miller cycle strategies paired with high intake manifold pressures on the combustion process, emissions, and thermal efficiency of heavy-duty diesel engines. Well-controlled experiments isolating the effect of Miller cycle strategies on the combustion process were conducted at constant engine speed and load (1160 rpm, 1.76 MPa net IMEP) on a single cylinder research engine equipped with a fully-flexible hydraulic valve train system. Late intake valve closing (LIVC) timing strategies were compared to a conventional intake valve profile under either constant cylinder composition, constant engine-out NO_x emission, or constant overall turbocharger efficiency (η_TC) to investigate the operating constraints that favor Miller cycle operation over the baseline strategy. Furthermore, utilizing high boost with conventional intake valve closing timing resulted in improved fuel consumption at the expense of sharp increases in peak cylinder pressures, engine-out NO_x emissions, and reduced exhaust temperatures. Miller cycle without EGR at constant λ demonstrated LIVC strategies effectively reduce engine-out NO_x emissions by up to 35%. However, Miller cycle associated with very aggressive LIVC timings led to fuel consumption penalties due to increased pumping work and exhaust enthalpy. LIVC strategies allowed for increased charge dilution at the baseline NO_x constraint of 3.2 g/kWh, resulting in significant fuel consumption benefits over the baseline case without compromising exhaust temperatures or peak cylinder pressures. As Miller cycle implementation was shown to affect the boundary conditions dictating η_TC, the LIVC and conventional IVC cases were studied at an equivalent η_TC point representative of high boost operation. With high boost, LIVC yielded reduced NO_x emissions, reduced peak cylinder pressures, and elevated exhaust temperatures compared to the conventional IVC case without compromising fuel consumption.

• 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: 2000842
• Alternate ID(s): OSTI ID: 2000844
• Journal Information: International Journal of Engine Research, Journal Name: International Journal of Engine Research Journal Issue: 2 Vol. 24; ISSN 1468-0874
• Publisher: SAGE
• Country of Publication: United States
• Language: English

Related Subjects

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