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Show wavelength zone generally range between 1.5-3.5 (n) and 0.5-2.0 (k). The absorption coefficient tend to decrease all the way till zero. Besides, the absorption coefficient obtained under different dispersion prediction value do not vary as much as the refractive indices. Figtse 8 illustrates the reason why the Drude-Lorentz dispersion model can very accurately predict the experimental value of soot refractive indices, which lies in the completely different effects the four major parameters, nf, nl, gl, gl, have on the refractive indices distribution curve: nf causes the curve end to rise abruptly; n t leads to an increase in curve ratio( almost equidistance ) ~ gl slightly reduces the curve end; and gl slightly reduces the curve front. These effects signify that one can roughly determine the tendency of the theoretical prediction curve distribution by the dispersion model through nf and nl, and then make detailed modifications through gl and g'l. 3.7 Optical Properties of Various Mediums in the Preheat Zone Figure 9 described the individual contributions of various gases and soot to the absorption coefficient and emissivity. The slope area in the figure is caused by the widening effect of specific wavelength consideration line of gases. Therefore, the optical properties of mediums in the preheat zone are the sum when both the soot and gas are considered. In this paper, we directly use the heat transfer numerical results obtained "under the conditions of a thin enough preheat zone and slow enough fuel flow velocity, in which the temperature distribution in this zone is regarded as a linear relationship". The numerical results are simplified in the non-isothermal wide band model. The figure demonstrates that soot distribution is continuous, and decreasing on the spectrum. Besides, the absorption coefficient is an order larger than the emissivity. Gas only exerts absorption and emission effects under specific wavelength. The major types of gas considered include H 10 ( more important at 2.7J..lm and 6.3J..lm ),45%, COl ( more important at 4.3~ ), 14%, CO( more important at 4.7J..lm ), 13% and CH4 ( more important at 3.3J.Un, 7.7JJ1n ),27%. In general, the greater the wavelength (Infrared region), the greater the optical effects, with CH4 being the only exception. IV. CONCLUSION The concrete results obtained in this study can be concluded as follows: (1) In the preheat zone at the flame front, as long as the thickness is thin enough., and the fuel flow velocity is slow enough, the temperature variation in this zone can be considered as having a linear increasing tendency. (2) Though heat conduction is very sensitive toward changes in the conduction parameter, Nt, and preheat thickness, to, the distribution variation in the preheat zone is very mild (macro perspective). The convection parameter, Nl , can aggravate the difference in conduction heat flux between the flame sheet and fuel surface, and change its distribution tendency. (3) The order of heat convection generally don't change dramatically as a results of such parameters as Nl , to, IDo . However, as the convection parameter, N1 , increases proportionally, and approaches flame sheet, there is also more energy taken away by the fuel flow. ( 4) The numerical results indicate that as the single scattering albedo, IDo, increases, the heat radiation that has increased from the fuel surface till the flame sheet, suddenly reverses its cour to decrease all the way. The other important discovery is that the maximum value of heat radiation did not occur on surface of the flame sheet, but close to the flame front regardless of the variation of other parameters. . 10 |