Thermal and environmental optimization of PCCI engine fueled with lemon seed biodiesel and dual gaseous fuels

This research investigates the performance, combustion, emission, and sustainability of a dual-fuel PCCI engine running on lemon seed oil methyl ester (LSOME) as base biodiesel, diesel as pilot fuel, and gaseous fuels—hydrogen (H 2 ) and methane (CH 4 )—supplied at 5 LPM. Cerium oxide (CeO 2 ) nanoparticles were added at 5, 10, and 15 ppm for improved combustion. Three blends of biodiesel (B10, B20, B30) were tested under full load conditions. Among all combinations, the B20D80H 2 -C15 blend achieved the highest performance with a 13.22 % increase in Brake Thermal Efficiency (BTE), 25.81 % reduction in Brake Specific Fuel Consumption (BSFC), 15.31 % reduction in CO, 7.32 % reduction in HC, 12.5 % reduction in smoke opacity, and a 15.2 % rise in peak cylinder pressure compared with diesel (D100). NOx emissions increased by 31.6 % due to higher in-cylinder temperatures. The B30D70H 2 -C15 blend also showed a 32.26 % reduction in BSFC and 17.65 % decrease in CO. Compared with pure methane, these blends provided modest synergistic improvements in efficiency yet greater economic viability. Using a sustainability assessment based on a Pugh matrix for multi-criteria comparisons, B20D80CH 4 -C15, B20D80CH 4 -C10, and B20D80CH 4 -C5 were identified as the best performing options (+10 score), while B20D80H 2 -C15 had a positive balance of performance and emissions (+8 score). These results clearly show that LSOME—hydrogen or methane enriched biodiesel with nano-additives of CeO 2 in PCCI engines has great potential to simultaneously provide high efficiency, low emissions and sustainability for future transport systems.