| OCR Text |
Show 1.3.17 region supporting individual flames along with the soot [4,5]. In flames where particulate concentration is high such as SRC-II oil flame [5], much of the heat release in the far-nozzle region occurs by the combustion of soot. The emulsification of fuel delays the evaporation rate of drops and lowers the rates of fuel pyrolysis and formation of soot. In SRC-II oil flame, the delayed evaporation of drops shifts the release of oxygen present in the fuel into the far-nozzle region. Further, the amount of soot burning in that zone decreases. The combined effect of these two factors manifests itself in an increase of 0~ concentration as noticed in Figure 3. In No. 2 oil flame, the decrease of soot concentration by emulsification [8] appears to be not large enough to result in a significant change in the rate of soot combustion in the far-nozzle region and consequently the oxygen concentration remains almost the same as in the neat oil flame. The temperature profiles shown in Figure 2 support the above explanation. The gas temperatures in the far-nozzle region of SRC-II oil flame are lower than those in the No. 2 oil flame because of higher radiant heat loss in the former. In flames with high particulate concentration such as the SRC-II oil flame, the overall ratio of soot to available oxygen concentration is large in the far-nozzle region. The emulsification reduces the soot concentration and thus shifts that ratio towards stoichiometric. Consequently, the oxidation rate of soot is enhanced and the temperature levels increase. However, in No. 2 oil flame, the reduction of soot caused by emulsification shifts the local soot/oxygen ratio away from stoichiometric and thus lowers the heat release rate and temperature levels in the far-nozzle region. If the |
