OCR Text |
Show 1.3.18 microexplosions of emulsion drops were strong, they should have resulted in an increase of temperature. On the contrary, the recorded temperature levels show a drop, and thus confirm that the microexplosions are weak in the far-nozzle region even if they occur and thus substantiate the findings of isolated emulsion-drop combustion studies [8]. The lower temperatures and lower rates of oxidation of soot in the far-nozzle region of SRC-11 oil flame than those in No. 2 oil flames also are manifested in the lower CO concentrations in the former. The emulsification of oils could enhance the hydroxy! radical concentration and thus increase the oxidation rate of CO to C02. Thus, CO decreases in both No. 2 and SRC-II oil flames. The release of fuel-bound oxygen in the far-nozzle region of SRC-II oil flame due to delayed fuel drop evaporation can further promote oxidation of CO. Hence, the decrease of CO emission is higher in SRC-II oil flame. The concentration of NO is much higher in SRC-II oil flame than in No. 2 oil flame because of the higher fuel-bound nitrogen of the former. The increase in the amount of fuel burning in the individual droplet-flame mode caused by emulsification results in a larger high-temperature reaction zone volume where NO is produced than that in the single flame enveloping the core of vaporizing droplets. Thus, in No. 2 oil flame, NO, produced mainly by thermal route, increases. In SRC-II oil flame, where the conversion of fuel-bound nitrogen is the dominant source of NO emission, the NO concentration changes very little over most of the cross section. That indicates the NO formation from fuel-bound NO is not very sensitive to fuel emulsification. Further clarification of this result needs detailed probing of minor species like PH, HCN, C in |