Catalytic Combustion of Pre-Vaporized Liquid Fuel

Fundamental characteristics of the catalytic combustion of vaporized kerosene spray were experimentally investigated. This study is a part of the development of a ceramic gas turbine engine for automobiles. Kerosene was used as a test fuel and its spray was injected from a swirl atomizer into a hot air stream. The inlet air temperature was elevated up to 900 K to vaporize the kerosene spray. Premixed gas of air and kerosene vapor was introduced into the catalyst. The total equivalence ratio was controlled from ϕ=0.18–0.32. The palladium catalyst was supported on a cordierite honeycomb monolith. Catalytic combustion phenomena were categorized in three typical states: (a) state of partial reaction in the catalytic monolith, (b) state of homogeneous reaction in the monolith, (c) state of homogeneous reaction with a blue flame supposed on the monolith. A parabolic shape blue flame in the state of (c) appeared downstream of the monolith. This flame was very stable and its temperature was relatively low compared with conventional premixed flames of hydrocarbon fuel because the equivalence ratio was much lower than those of premixed flames. The distance from the monolith to the ignition point of this flame became short with a rise of the inlet air temperature, even if the volumetric airflow rate increased with the air temperature. Spontaneous emission spectra of radiation from the blue flame were measured. Strong spectral peaks of OH, CH, and $CO+$ radicals were observed in the spectra. This spectral structure was quite different from that of a blue flame of premixed propane.