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Abstract
Results of a theoretical-experimental study of the contribution of radiation to the ignition of coal-water fuel (CWF) flames are reported. The calculation of radiation absorbed by the fuel spray is based on detailed radiation measurements in the ignition zone of three CWF–flames.A simple model to calculate the ratio of radiative to convective heal transfer (11) to the particles in a coal-water slurry fuel spray during its heat-up to ignition is presented. Input data for the model were provided by in–flame measurements and by an ignition model (Walsh et al., 1984).Two limiting cases were calculated for the theoretical heat transfer ratio. 11. the upper limit being the hemispherical radiation incident on a single particle, and the lower limit the narrow angle radiation incident on a cloud of particles. These values of II were then compared with those calculated from experimental data on the absorption of radiation by the fuel spray.The influence of the fuel particle size, the temperature of the gas entrained into the fuel spray, and of the particle temperature history (heat-up, vaporization, ignition times), upon the ratio of radiative to convective heat transfer to the fuel spray is discussed.