Combustible mixture produced from catalytic combustion of pre-vaporized liquid fuel

摘要

Combustion phenomena of a reactive gas that was partially burned on a catalyst were investigated. When an evaporated liquid fuel like kerosene was supplied into a catalytic combustion system, a blue flame was observed in a post-catalytic gas stream. It was considered that a reactive gas formed by a partial combustion in the catalytic monolith was burned with a gas phase reaction. It was called a thermal combustion flame. In this study, compositions of the reactive gas and spontaneous emission spectra from the blue flame were experimentally analyzed. Kerosene was used as a test fuel and its spray was vaporized in a hot air stream. A mixture of air and kerosene vapor was introduced into a cordierite honeycomb monolith that was coated with palladium. Concentrations of CO, HC(C{sub}1…C{sub}7) and NO, and temperature distribution in a reactive gas stream were measured to clarity a reaction mechanism of a post-catalytic combustion. Further, high molecular species(C{sub}8…C{sub}15) in the combustible gas were trapped by the water-cooled condenser system and they were analyzed by the gas chromatograph. The main result obtained here are as follow. The post-catalytic reaction was slowly progressed in the gas stream after catalytic monolith when the mixture was insufficiently burned in the monolith. Between the honeycomb and the thermal combustion flame, there are high molecular species similar to the kerosene vapor. They decreased near the front of the thermal combustion flame. The concentrations of lower hydrocarbon and CO were slowly increased by thermal dissociation of fuel vapor and higher hydrocarbons. When the temperature and concentrations of lower hydrocarbons and CO increased up to critical levels of an auto-ignition, a blue flame was established in the stream. Spontaneous emission spectra from the blue flame were measured. Strong spectral peaks of OH, CH, CO radicals were observed in the spectra. This spectral structure was quite different from that of a premixed flame of kerosene vapor.