Emission reduction in CI engines using nannochloropsis biodiesel with cooled EGR: A comparative approach

• The performance analysis showed that BTE of the B20 blend was comparable to diesel, with only marginal consequences due to its lower calorific value, while BSFC increased moderately at higher EGR levels. • Emission analysis revealed that the B20 blend with EGR achieved lower CO and smoke opacity than diesel at light and medium loads, owing to the oxygenated nature of biodiesel, but showed slightly higher HC emissions at higher EGR rates and heavy loads. • NOx emissions, initially higher for biodiesel without EGR, were substantially reduced with increasing EGR, demonstrating the effectiveness of EGR in suppressing thermal NOx formation. The increasing demand for renewable and sustainable fuels has driven interest in biodiesel as a substitute for conventional diesel in compression ignition (CI) engines. In this study, Nannochloropsis oil methyl ester (NOME) was produced and blended with diesel at 20% B20 and experimental investigations were carried out under different engine loads EGR rates of 10%, 15% and 20%. CP and HRR were measured with full load at baseline 0% EGR, diesel showed a peak cylinder pressure of 70 bar, compared to 67 bar for NOME B20. With 10% EGR increased NOME B20 peak pressure to 69 bars due to longer ignition delay, while 15% and 20% EGR reduced it to 66 bar and 64 bar. HRR rose from 60 J/ °CA (0% EGR) to 65 J/ °CA at 10% EGR, then dropped to 58 and 55 J/ °CA at 15% and 20% EGR. Performance analysis diesel shows a BTE of 31.1% and NOME B20 are 30.5%, decreasing gradually with EGR. BSFC increased at full load, diesel consumed 0.180 kg/kWh and NOME B20 required 0.190, 0.200, 0.210 and 0.230 kg/kWh for EGR variations. Emission analysis showed that CO emissions for NOME B20 lower than diesel at lower loads, but increased with higher EGR rate increase to 0.102% at 20% EGR at full load. HC emissions increase from 40 ppm with 0% EGR to 52 ppm 20% EGR. NOx emissions showed a considerable reduce with EGR, from 933 ppm 673 ppm at various EGR rates. Smoke opacity for NOME B20 from 45% with 0% EGR to 53% with 20% EGR and compared to 51% for diesel at full load. The combined use of NOME B20 and optimized EGR achieved a favorable balance between performance and emission characteristics.