Influence of pilot diesel ratio and engine load on combustion behaviour in a biogas-fueled RCCI engine

The present study aims to analyse the combustion-related parameters in a reactivity-controlled compression ignition (RCCI) engine with a dual-fuel approach for diesel and biogas fuels. The objective is to investigate how varying biogas energy share ratios (50 %, 60 %, 70 %, and 80 %) affect combustion behaviour at different engine loads (40, 60, and 80 Nm). All tests were conducted at a constant engine speed of 1750 rpm. Results from dual-fuel operation were compared to baseline diesel combustion. The findings indicated that an increase in the biogas addition generally resulted in the deterioration of combustion stability, as evidenced by elevated ignition delays and COV IMEP values. However, this negative impact was mitigated at higher engine loads and increased diesel pilot ratios. As the quantity of biogas increased, a rise in cylinder pressures, pressure rise rates, ignition delays and ringing intensities was observed. Conversely, combustion stabilities, peak heat release rates and combustion durations all decreased. This research contributes to advancing sustainable practices in engine technology by promoting alternative fuel adoption in internal combustion engines, aligning with efforts to enhance energy efficiency and sustainability in the transportation sector. • The combustion characteristics of a diesel-biogas dual-fuel RCCI engine are experimentally analysed. • Engine performance is evaluated under varying pilot diesel ratios (20–50 %) and torque levels (40–80 Nm). • Dual-fuel study is found to increase ignition delay and combustion duration, while reducing combustion stability. • Biogas improves the in-cylinder pressure and HRR when compared to the pure diesel operation. • Ringing intensity is higher for dual-fuel operation, however, maintaining the acceptable limits.