Experimental analysis of combustion dynamics in an NH3-biodiesel dual fuel diesel engine under varying ammonia flow rates

This study investigates the combustion characteristics of a single-cylinder, direct injection agricultural diesel engine operated in dual-fuel mode using ammonia (NH 3 ) as the primary fuel and a 20% Jatropha methyl ester–diesel blend (JME20) as the pilot fuel. Experiments were performed at four NH 3 flow rates (8,10,12 and 16 lpm), designated DFX through DFX3, were evaluated over the full load range (0–100 %) at1500 rpm constant speed. Key combustion metrics such as peak in-cylinder pressure (PCP), heat-release rate (HRR), ignition delay (ID), combustion duration (CD), mass-fraction-burned (MFB), and cumulative heat release were recorded via high-resolution crank-angle data. The results demonstrate that NH 3 induction prolongs ignition delay and broadens combustion duration in proportion to flow rate. At 12 lpm (DFX2), the engine recorded the optimal combustion performance, achieving a peak pressure of 58.6 bar, an increase of 3.2% over 8lpm (DFX) and 5.8% over 10 lpm (DFX1). However, at 16 lpm (DFX3), peak pressure dropped to 56.4 bar, suggesting over fumigation may suppress pressure development. These findings confirm that NH 3 fumigation can tailor combustion characteristics and enhance energy release, with 12 lpm (DFX2) identified as the optimal flow rate for achieving improved combustion stability and performance in NH 3 –biodiesel dual fuel engines.