Akademik Veri Yönetim Sistemi
Case Studies in Thermal Engineering, cilt.68, 2025 (SCI-Expanded)
Natural gas/diesel dual-fuel combustion is a novel technique that offers high thermal efficiency and reduced emissions without requiring extensive hardware changes or complex aftertreatment systems. Previous study conducted on the same setup has shown that increasing the diesel mass split ratio (SR) between two injections and advancing the start of first injection (SOI1) improved NOx, HC emissions, and combustion efficiency. In this study, in-cylinder flow, spray and combustion was simulated in computational fluid dynamics (CFD) software to reveal the effects of variable SR and early SOI1, enabling e-pilot combustion. First, experiments at 50 % and 70 % SR were validated, and additional cases (85 and 92.5 %) with higher SR were analyzed via CFD simulations. Low and high temperature reactions are investigated using formaldehyde (CH2O) and OH radicals, respectively. Increasing SR delays low and high-temperature reaction phases. Initial OH formation occurs near the cylinder wall at SR = 50 % and shift toward the center as SR increases. Higher SR and advanced SOI1 result in decreased Pmax and retarded combustion. CFD results show that unburned HCs effectively decrease with increasing SR. Advancing SOI1 results in a greater decrease in NOx emissions than an increase in HC emissions. Increasing SR decreases both NOx and HC emissions, increases gross indicated power by up to 3.9 %, and reduces specific fuel consumption by 2.5 %. The early pilot (e-pilot) strategy used in this work effectively controls fuel-temperature stratification and emissions by controlling low and high-temperature reactions.