Experimental study on reducing BC emissions from a low-speed marine engine by using blended biodiesel and a nitro additive

The aim of this study was to evaluate the emission reduction effect of using waste oil biodiesel/diesel binary fuel and a nitro additive on black carbon (BC) emissions from a large marine engine fueled by heavy fuel oil (HFO). We conducted steady-state conditions tests on a low-speed two-stroke marine engine, where pure distillate diesel (D100), blended biodiesel (blending ratios of 10%, 30%, and 50%), low-sulfur heavy fuel oil (LSFO), high-sulfur heavy fuel oil (HSFO), and a nitro additive were tested, and the BC emission concentrations from the engine were measured under different conditions using a filter-type smoke meter (FSM) and a photoacoustic smoke meter (PAS). The results indicated that BC emissions from the engine were significantly decreased when blended biodiesels were used, with the decline rate increasing as the engine load increased, reaching a maximum reduction of 73% and 94% under 75% and 100% load compared to the use of HFOs, respectively. However, the use of biodiesel slightly increased the brake specific fuel consumption (BSFC) and NOx emissions. The nitro additive was blended with LSFO and HSFO at a ratio of 1:1200, respectively. It was observed that the introduction of the nitro additive led to a significant reduction in compared to the use of pure HFOs. But different from the case of using blended biodiesels, the decline rate of BC decreased with increasing engine load. The BC emissions from LSFO and HSFO were decreased by approximately 10% and 25% under 25% load, respectively, the corresponding BSFC decreased by 5.88% and 3.71%, respectively, while the NOx emissions increased by 11.59% and 34.58%, respectively. In addition, the BC emissions measured by the FSM were on average 38.56% and 43.53% higher than those of the PAS when LSFO and HSFO were used, respectively.