Influence of rice husk derived nano-silica on performance, emissions, and combustion characteristics of diesel engine fueled with baobab biodiesel

The increasing number of on-road automobiles as a result of an exponential increase in population and lifestyle places enormous strain on depleted fossil petroleum fuel, energy security, and environmental stability. This situation drives researchers to find an alternative source to replace petroleum diesel. Biodiesel is one of the promising viable substitutes. However, biodiesels may not always fulfill the EN 14214 standard due to differences in fuel properties. This could cause issues with engine operation and emissions. This study therefore aims to use novel nano-silica (SiO2) additives extracted from rice husk to improve its fuel properties. Also focuses on the influence of additives on the operation of the compression ignition (CI) engine. The Adansonia digitata methyl esters (ADME) were made by transesterification process, The physicochemical properties of the fuels with and without additives were measured as per ASTM D6751 and EN 14214 standards methods, and nano silica was analyzed by Thermogravimetry (TGA), Fourier transform infrared spectroscopy (FT-IR), Brunauer Emmett Teller (BET), X-ray diffractometer (XRD. Barret-Joyner Halenda (BJH) pore diameter, specific surface area, and pore volume of SiO2 were observed to be 19.3 nm, 502.24 m2 /g, and 0.761 cm3 /g, respectively. At 400 and 800 ppm dose levels, the oxidation induction period (OIP) increased dramatically, peaking at 10.03 h. The stability of ADME has significantly improved, as evidenced by these results, meeting the >3 h and >8 h standard limits set by ASTM D6751 and EN 14214, respectively. The viscosity of B100 decreased with increasing additive content, from 4.62 mm2 /s for neat B100 to 2.21 mm2 /s for 400 ppm. Cetane number (CN) (60 to 64). All nano-fuel blends used in engine tests were prepared by an ultrasonication process. The results revealed that the brake thermal efficiency (BTE) at maximum brake powers (BP) for B20, B20+SiO2, B100, and B100+SiO2 fuels were 29.9, 28.2, 28.44, and 27.1%, respectively, and brake-specific fuel consumption (BSFC) was reduced as the load increased. The peak heat release rate (HRR) of the B100+SiO2 and B20+SiO2 are slightly higher by 2.9 and 2.6%, respectively, than the neat B100 at medium BP. However, in-cylinder gas pressure (CGP) increased following the order of B20+SiO2<B20<B100<B100+ SiO2<B0. Moreover, the exhaust emissions of nano-fuel blends exhibited a greater reduction of CO, THC, CO2, NOX, and particulate matter (PM) compared to B20 and B100. Overall, this study recommends that SiO2 nano-additive is a good substitute fuel additive to use with biodiesel and its blends because of the improved properties of biodiesel, decreased emissions, and increased engine performance efficiency