Impact of nanoparticles and butanol on properties and spray characteristics of waste cooking oil biodiesel and pure rapeseed oil

Renewable biofuels can offset greenhouse gases by replacing fossil fuels destined for internal combustion engines. However, biofuels have their own setbacks and may lead to poor combustion inside the engine cylinder. In this study, nanoparticles and butanol were blended either separately or together with waste cooking oil biodiesel and neat rape seed oil to investigate the impact of these additives on the properties and spray characteristics. The investigation comprised of three stages, with each having an effect on how the next stage of the investigation was conducted. Initially, the physicochemical characteristics of 25ppm, 50ppm, 75ppm and 100ppm concentrations of aluminium oxide and copper oxide nanoparticle blends with fossil diesel, waste cooking oil biodiesel and rapeseed oil were investigated. The results from first stage investigation showed that, in general, blends containing aluminium oxide nanoparticles gave better results for almost all the concentrations when compared with copper oxide nanoparticle blends with the same nanoparticle concentrations. Overall, waste cooking oil biodiesel blended with 100ppm aluminium oxide nanoparticle showed most promising results like the flash point of 159.3°C, kinematic viscosity @40°C of 4.66 cSt, and gross calorific value of 44.43 MJ/kg. These values were 61.6% higher, 51.3% higher and 3.2% lower than that of corresponding fossil diesel values. Subsequently, in the second stage of the study, the addition of butanol was investigated to assess its ability to enhance the emulsion of biofuel-nanoparticles blends. Four blends containing 90% biodiesel & 10% butanol, and 90% rapeseed oil & 10% butanol, with and without 100ppm Al2O3 were prepared. Results showed that the kinematic viscosity of the fuel blends containing 100ppm aluminium oxide nanoparticles were decreased by 0.4% and 3.3%, for 90% biodiesel & 10% butanol and 90% rapeseed oil & 10% butanol blends respectively, when compared to without the nanoparticles. The results obtained from the second stage of investigation proved that butanol acted as a surfactant and thus addition of butanol helped to improve the properties of the biofuel-nanoparticle blends. In the third stage of the study, the spray characteristics of fossil diesel, biodiesel, biodiesel + 100ppm aluminium oxide nanoparticles, rapeseed oil, rapeseed oil + 100ppm aluminium oxide nanoparticles, 90% biodiesel & 10% butanol, 90% biodiesel & 10% butanol + 100ppm aluminium oxide nanoparticles, 90% rapeseed oil & 10% butanol and 90% rapeseed oil & 10% butanol + 100ppm aluminium oxide nanoparticles were investigated. It was found that amongst all fuels, blend containing 90% biodiesel + 10% butanol + 100ppm aluminium oxide nanoparticles gave better spray characteristics; for example, the liquid sheet angle was 7.14% lower and the spray cone angle was 7.87% higher than the corresponding fossil diesel values. The study concluded that the spray characteristics and properties of biofuels could be improved by blending with both aluminium oxide nanoparticles and butanol.