Ignition of a fuel spray by a hot surface

Abstract

An experimental study of the ignition of Jet-A fuel sprays by an isothermal hot surface was conducted in a vertical axisymmetric duct. The ranges of flow conditions under which ignition was investigated were: 1) freestream velocity, 1-5 m/s; 2) boundary-laye r momentum thickness, 3-20 mm; 3) freestream air temperature, 40-250°C; 4) fuel concentration, ignitability limits; and 5) droplet size (SMD), 20-200 /im. In addition to measurements of the wall temperature necessary for ignition under the above conditions, local measurements of velocity, turbulence intensity, fuel concentration, and the fraction of fuel vaporized were measured in the boundary layer at surface temperatures just below that required for ignition. The results exhibited vapor ignition trends for most of the flow conditions, with some exceptions where single-droplet ignition appeared to be present. The experimental data are compared with existing vapor ignition theory.