The use of the high viscous biofuel results in poor combustion efficiency. Utilization of the biofuel on the existing engine is challenging due to the higher fuel pump force requirement and atomization effects. Hence, in this study, the spray characteristics have been examined in addition to the typical combustion and emission characteristics. In general, spray properties changes are based on the viscosity of the fuel used. Utilizing the higher viscous fluid in the engine creates havoc on liquid penetration and vapor penetration. A series of tests was conducted in the single-cylinder four-stroke diesel engine fuelled with Jatropha Curcas. The biodiesel blends were prepared at three different combinations of 10%, 20%, and 30% dispersed with the Fe2O3 nanoparticles at 50 ppm to form JF10 (10% blend + 90% diesel with 50 ppm of Fe2O3), JF20 (20% blend + 80% diesel with 50 ppm of Fe2O3), and JF30 (30% blend + 70% diesel with 50 ppm of Fe2O3). Based on the previous study observation, adding the blends affects the both combustion and performance of the engine which is counteracted in this study by adding the nanoparticles to the blends. From the obtained results, it is proved that the addition of nanoparticles increases the engine performance and emission characteristics. To be precise, the brake thermal efficiency has been improvised by 4% for the JF10 compared to neat diesel. With regard to emissions, a massive reduction in CO and NOx has been observed. To understand the quality of combustion, the fluid spray simulation has been carried out. A set of numerical simulations were done using the particle droplet analysis with the aid of star ccm+ and found that injection pressure and ambient pressure are the key responsible parameters for increasing the combustion efficiency of the system. On the other hand, the liquid length of blended fuel is another key factor that affects the atomization process. Furthermore, the high injection pressure reduces the spray cone angle for biodiesel by achieving high mixing rates.