| OCR Text |
Show Figure 11 shows the effect of equivalence ratio on oxidation, where the oxidized layer thickness, '[; A' is plotted against the surface temperature. Oxidation proceeds rapidly with the temperature rise of a steel plate for near stoichiometric mixtures, _ but for richer mixtures slight oxidation proceeds with the initial temperature rise and distinct reduction occurs thereafter at higher temperatures. The observed thicknesses for the cases richer than g; 1 3A =1 .17 are acceptable as the "nonoxidized" surface. The relation between oxidized layer thickness and local gas compositions are shown in Fig.12. The "nonoxidized" surface requires such local gas compositions that the residual oxygen concentrations is lower than 0.1% by volume and the ratios of CO/C02 and H2/H20 are over 0.4 and 0.09, respectively, as far as the -stable species are concerned. To clarify the generality of the above criteria the effects of the carbon monoxide addition to methane fueled flames were studied. The oxidizing behavior and the change in local gas compositions of CO added flames are shown in Fig.13. The addition of CO to the city-gas/air mixture of a constant equivalence ratio, P13A' increased the total equivalence ratio, ¢t' and the ratios of CO/C02 and H2/H20. The residual oxygen concentration and the oxidized layer thickness, in contrast, decreased with the CO addition. Judging from the variation in the oxidized 120 Q " Ii 80 0 • E ~o E <C t-J 20 10 0, )A I. 05 1.15 1.17 1. 20 1. 25 600 T 1500 1000 E c - 500 - 300 200 100 a lQOO -- '---- l U) Fig. 11 E_~~.~cts of equivalence ratio and steel plate temperature on oxidation 11 |
