Biodiesel obtained from renewable sources is an auspicious alternative to regular diesel due to its sustainability and low environmental impact. This study examines the influence of carbon nanotube (CNT) additives on the operation and emission features of a compression ignition engine using Hevea Brasiliensis biodiesel (HBBD20) fuel along with CNT mixed blends (HBBD20 CNT 30 ppm, HBBD20 CNT 60 ppm, HBBD20 CNT 90 ppm and HBBD20 CNT120 ppm). The experiments were performed on a direct injection single piston four stroke diesel engine to measure key parameters like brake thermal efficiency (BTE), specific energy consumption (SEC) and emission values (CO NOx unburnt hydrocarbons (UBHC) and smoke opacity. The results showed that HBBD20 CNT 120 ppm gave the best performance, with 1.98% rise in BTE over HBBD20 and a 5.95% drop in SEC, showing better fuel use. CO emission were reduced by almost 29.68% and UBHC lowered by 50.54%, which is better than diesel. With the inclusion of CNT particles NOx emission showed a gradual fall, and HBBD20 CNT 120 ppm achieved about 9.75% lower than diesel. Smoke emission were also reduced effectively by 44.92 % in HBBD20 CNT120 ppm, indicating improved combustion efficiency. The findings indicated that CNT additives improve combustion and fuel economy while decreasing exhaust gases. Among the tested blends, HBBD20 CNT 120 ppm was the most efficient balancing performance benefit and emission control, making it useful choice for sustainable energy uses. This work also shows the potential of CNT added biodiesel in lowering environmental pollutants while still keeping acceptable engine efficiency and performance.
