Combustion behaviour and emission trends of diesel–jp8 blends in a single-cylinder diesel engine

This study investigates the effects of blending JP8 fuel with conventional diesel on engine performance, combustion characteristics, and exhaust emissions in a single-cylinder, four-stroke, direct-injection diesel engine. Tests were conducted at 1800 rpm under five torque loads (0, 8, 16, 24, and 32 Nm) using three fuel types: pure diesel, 90% diesel–10% JP8 (90D10JP8), and 70% diesel–30% JP8 (70D30JP8). Results showed that at low loads (8 Nm), JP8 blends exhibited higher BSFC values (e.g., 404.1 g/kWh for 70D30JP8 vs. 376.4 g/kWh for diesel) and lower BTE (20.54% vs. 21.89%), consistent with prior findings on JP8’s lower cetane number and volatility. However, at full load (32 Nm), both JP8 blends achieved better BSFC (249.19 g/kWh for 70D30JP8 vs. 277.96 g/kWh for diesel) and higher BTE (33.31% vs. 29.64%), indicating improved combustion under high thermal loads—a trend also observed in studies on kerosene-based blends enhancing atomization at elevated temperatures. Combustion analysis revealed that JP8 blends delayed ignition (e.g., CA10 at -2.29°CA for 70D30JP8 vs. -3.20°CA for diesel) and prolonged combustion duration at mid-loads (26.68 CAD for 70D30JP8 at 16 Nm vs. 23.93 CAD for diesel), in line with literature describing increased premixed fractions due to lower cetane number. Despite this, maximum in-cylinder pressure surpassed diesel at 16 Nm (76.88 bar for 70D30JP8 vs. 72.76 bar for diesel), indicating stronger premixed combustion. Emission results confirmed CO reductions at full load for JP8 blends (0.402% vs. 0.834% for diesel) and notable soot suppression at mid-loads (e.g., at 24 Nm: 0.46% for 70D30JP8 vs. 8.57% for diesel), consistent with JP8’s lower aromatic content. However, NOx emissions increased at mid-to-high loads (e.g., at 32 Nm: 999 ppm for 70D30JP8 vs. 930 ppm for diesel), highlighting a trade-off due to higher local combustion temperatures. Overall, this study expands existing knowledge by providing a detailed, load-dependent evaluation of JP8–diesel blends, showing that blends—particularly at 30% JP8 can achieve comparable or superior performance at high loads while reducing CO and soot emissions, although NOx mitigation strategies remain essential for practical application.