Optical soot measurement of bio-butanol upstream product, ABE (Acetone-Butanol-Ethanol), under diesel-like conditions

ABE (Acetone-Butanol-Ethanol), the upstream product of bio-butanol, is considered as a promising alternative fuel for IC engine. Two-dimensional soot distribution and soot mass of spray combustion of ABE and diesel was measured by forward illumination light extinction (FILE) technology. The ambient temperature and oxygen concentration of injection was varied from 1200 K to 900 K and 21% to 11% to represent normal temperature combustion and low temperature combustion modes respectively. It was found that soot distribution area and intensity of ABE, especially ABE with a high acetone fraction, is much lower than that of diesel. The soot clouds area and intensity increase with increasing ambient temperature and decreasing oxygen concentration, but the increased scale of soot for ABE is much lower than that of diesel. Quantitative results of soot mass for ABE show that the soot increases rapidly with increasing ambient temperature at lower oxygen concentration conditions because the soot producing rate is largely increased when elevating temperature, while the soot oxidation rate remained slow due to the insufficient oxygen. Based on analysis, it was found that clean combustion of ABE benefited from a lean air-fuel mixture because of the great volatility and low stoichiometric ratio of the fuel, and the competition of Carbon atom between CO and C₂H₂ in the pyrolysis reactions that reduced the soot source materials. Overall, as an alternative IC fuel, ABE is able to achieve much lower soot than diesel and is able to maintain clean combustion in a large range of environmental conditions.