A Computational Investigation of Fuel Chemical and Physical Properties Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

Abstract

Gasoline compression ignition (GCI) offers the potential to reduce criteria pollutants while achieving high fuel efficiency. This study aims to investigate the fuel chemical and physical properties effects on GCI operation in a heavy-duty diesel engine through closed-cycle, three-dimensional (3D) computational fluid dynamic (CFD) combustion simulations, investigating both mixing-controlled combustion (MCC) at 18.9 compression ratio (CR) and partially premixed combustion (PPC) at 17.3 CR. For this work, fuel chemical properties were studied in terms of the primary reference fuel (PRF) number (0–91) and the octane sensitivity (0–6) while using a fixed fuel physical surrogate. For the fuel physical properties effects investigation, six physical properties were individually perturbed, varying from the gasoline to the diesel range. Combustion simulations were carried out at 1375 RPM and 10 bar brake specific mean pressure (BMEP). Reducing fuel reactivity was found to influence ignition delay time (IDT) more significantly for PPC than for MCC. 0D IDT calculations suggested that the fuel reactivity impact on IDT diminished with an increase in temperature. Moreover, higher reactivity gasolines exhibited stronger negative coefficient (NTC) behavior and their IDTs showed less sensitivity to temperature change. In addition, increasing octane sensitivity was observed to result in higher fuel reactivity and shorter IDT. Under both MCC and PPC, all six physical properties showed little impact on global combustion behavior, NOx, and fuel efficiency. Among the physical properties investigated, only density showed a notable effect on soot emissions. Increasing density led to higher soot due to deteriorated air entrainment into the spray and the slower fuel-air mixing process.