COMBUSTION OF BORON NANO-PARTICLES IN ETHANOL SPRAY FLAME

Biofuels such as ethanol have lower energy density than conventional petroleum-based fuels, and therefore enhancing its energy density via addition of high-energy density components is an attractive option. Boron is an attractive fuel additive because it has among the highest volumetric heating value among potentially suitable additives. The present study deals with an experimental investigation of boron combustion in an ethanol spray flame. A constant low particle loading density of boron nanoparticles (60nm SMD), around 1% (by weight) of the liquid fuel flow rate, has been used. Though it has high energetic potential, the combustion process of boron is retarded by the initial presence of the oxide coating the particle surface. In the present study, measurements have been made of the emission of intermediate sub-oxide like BO2 using spectroscopy and imaging with interference filters. The effect of boron on the hydrocarbon combustion has also been studied by examining the heat release and product mole fractions. In addition, particle characterization has been carried out to know the size, surface structure/composition of the injected boron nano powders using XRD, XPS and TEM. A preliminary investigation has also been performed on the burnt particle collected from the exhaust structure using XRD. The chemiluminescence and spectroscopic signatures indicate that boron combustion is facilitated and that hydrocarbon combustion is enhanced. The particle analysis shows differences in the imaged and spectroscopic characteristics of the unburnt and burnt nano-particles reflecting the particle-combustion processes.