Experimental exploration of additive NGQD as a performance and emissions improver of the C.I. engine with biodiesel–diesel blends

A novel investigation on effects of mixing the synthesized additive nitrogen-doped graphene quantum dot (N-GQD) with biodiesel as an alternative fuel to fossil diesel in a compression ignition engine is carried out. Also it is aimed to develop a strategy for feasibility of higher rates of biodiesel in a blend with achieving improved emissions and high efficiencies of the engine. For this, the biodiesel extracted from non-edible rapeseed oil is tested at different proportions of 50%, 75%, and neat (100%). The synthesized N-GQD was prepared from citric acid and urea within a short span (15 min) and Raman spectral calculations estimated ~ 19 nm domain size. The testing of N-GQD proportions includes 50 ppm, 75 ppm, 100 ppm and 150 ppm. A sought for simultaneous improvement in performance, combustion, and emissions of the engine, and blends of diesel–biodiesel mixed with additive N-GQD at different proportions are prepared and tested. A comparison of engine parameters at different operating conditions found an optimum improvement in brake thermal efficiency by 2–3%, brake specific fuel consumption by 4.5%, carbon monoxide by 43%, unburnt hydrocarbons by 39% with a slight increase of nitrogen oxides by 5.5% for the blend BL6-D50B50A100ppm (diesel 50% + biodiesel 50% + additive 100 ppm) compared to neat diesel at 90% of full load. As a NOx controlling technique, recirculation of exhaust gas at 15 vol% rate, reduction of 13.5% observed for the blend. These results show that N-GQD additive with biodiesel improved emissions and performance that shed new light on the viability of using higher biodiesel rates in the engine.