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Show 3.5 The Effects on the Total Heat Auxes Figure 6(a) indicates that as Nl increases, the scale of the total heat fluxes demo~trates fluctuating changes. This is dominated by heat conduction, where the effects of heat convectIon and heat radiation are canceled each other. N 1 ~ 10 the total heat fluxes generally fall between -10 and O. N 1 > 10 the total heat fluxes increase steeply as N 1 increases. The observation of changes of N2 from 0.01 to 20 in Figure 6(b) reveals that as N2 increases, two different tendencies of total heat fluxes may occur. This is dominated by heat convection, where the effects of heat conduction and heat radiation are canceled each other. N2 ~ 0.1 the total heat fluxes are a line almost without any changes. N2 > 0.1 the total heat flux curve gradually increases at first, and then rapidly while approaching the flame sheet. This phenomenon also intensifies as N2 increase. The observation of changes of to from 0.001 to 4 in Figure 6(c) indicates that the scale of total heat fluxes shows fluctuating steep increases as to increases. This is dominated by heat conduction, where the effects of heat convection and heat radiation are canceled each other. to < O. 1 there are dramatic changes in the total heat fluxes as a result of an increase in to · to ~ 0.1 the total heat fluxes almost overlap into a line without changes. Figure 6( d) indicates that overall the total heat fluxes do not vary very much unless when approaching the fuel surface, where the fluxes decrease as Clo increases. This is dominated by heat convection, where the effects of heat conduction and heat radiation are canceled each other. The above analyses show that parameters Nl and to have the most significant effects on total heat fluxes, followed by N2 and Clo . 3.6 Prediction of the Optical Properties of Soot by the Drude-Lorentz Dispersion Model There are two types of theories involving gas in the research of medium radiation: narrow band model (suitable for micro analysis of experimental measurement), and wide band model (suitable for macro analysis of the gas leve~ adopted in this paper). The theoretical framework of soot is based on the Drude-Lorentz dispersion model to derive the optical properties of soot, and further infer the absorption coefficient and emissivities of soot. Table 1 lists the values of dispersion constants used by different researchers (to match the dispersion model and experimental values). Generally speaking, bound electron frequency and free electron resistance constants maintain a constant value( Clll = 1.25,Cll2 = 7.25,gr= 1.2 ) without any major changes. Therefore, the different values adopted by different researchers to match the soot optical measurement values focus on the electron density( nr, n,) and resistance constant( gl ,g2 ). It is important to note that the researchers before Lee and Tien( 1981) did not distinguish between the mass of the bound and free electrons, so that the data listed in the table indicate an obvious difference between the constant values taken in earlier studies and those taken in later ones. The soot sampling methods used were also different. Stagg, etc.( 1993) ground soot retrieved from the flame for research, while the other researchers directly measure the optical properties of soot in the flame. In Figure 7, the above dispersion values used by different researchers are incorporated in the Drude-Lorentz dispersion model to derive the soot refractive indices( n & k ), to further infer the absorption coefficient( le)., ) . Generally speaking, the refractive indices tends to slightly decrease first in the visible and Infrared( 0.4 - 1 O~ ), and then increase from then on. Besides, its changes in this 9 |