| OCR Text |
Show 7 wide distribution. The radial distribution of radical species at each level of oxygen enrichment is shown in Figures 16(a)-(c). In each figure is shown the distribution when the combustion reached the central axis. W h e n the oxygen concentration of combustion air is raised, H increases much more than other radicals. 4.4. Estimate of Reducibility and Reduction Mechanism Figure 17 and 18 show the relation between the mole ratio of H/(0-fOH) and the preheating air temperature, and oxygen enrichment. The larger this ratio is, the higher the reducing ability is. However, because neither the oxidation nor the reducing ability of each radical species with iron is clear, the threshold ratio of the oxidation/reduction cannot be estimated. In qualitative evaluation, the mole ratio of H/(0+OH) increased gradually as preheating air temperature rises as shown Figure 17. And this ratio increased rapidly as the oxygen concentration rises as shown in Figure 18. This computation result corresponds to the experimental result where the reducing ability of the oxygen enriched combustion was higher than that of the preheated air combustion. From the above-mentioned analytical results, the combustion formed by the SNM burner, which is a turbulent flow diffusion flame, is thought to be as follows. 1) S N M burner, nozzle-mixed type, has local concentration distribution at early stages of combustion. 2) At this time, C H 2 0 is generated in the low temperature and excess fuel containing region, and H, 0 and O H are generated in the high temperature region. 3) A s the flame temperature rises, C H 2 0 is consumed immediately by the thermal decomposition reaction. 4) H, O and O H are predominant radical species in high temperature and reactive stage. 5) These radical species are increasingly generated with higher temperature resulting form air preheating or oxygen enrichment 6) In the case of low air ratio combustion, H is generated more than O and OH. In this numerical analysis, only the reaction in the flame was considered. However, there is another analytical result where the flame structure changes as a result of the flame being cooled during the blowing of the steel sheet.6) A detailed analysis of this is necessary. |
