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Show where c! = 1.6022 x 10-19C: the electron charge. m = 9.11 x 10-31 kg: the electron mass in vacuum. . m· = ml 18 : the effective mass of the free electrons due to move in a crystal lattice. Eo = 8.854 x 10-l2ClIN· m" : the permittivity constant. n",(i = 1,2),n[: the bound and conduction electron number densities respectively. C>b,(i = 1,2): the resonance frequency of bound electrons i. ro: the frequency of the interacting radiation. Spectral Absorption (or Extinction) Coefficient KA = ~A = 361rllk (I'll 1 (22) (n2-k2 +2)2 +4n"k2 ~A) (only valid to very small and spherical soot particles) (v : volume fraction of soot, usually between 1 O~ and 10-4 m. RESULTS AND DISCUSSION With the temperature ratio and surface emissivity between the fuel face and the flame sheet at TilT" = 0.2, E 1 = 0.8 and E2 = 0.95, the four important parameters of conduction( Nl ), convection( N" ), the optical thickness( to ), and the single scattering albedo( roo ) were used to study the numerical results of the temperature and heat transfer distribution in the preheat zone. 3. 1 The Effects on Temperature Profiles Figure 2(a) indicates that as NI increase (i.e. the role of conduction becomes mor important), the temperature gradient closer to the flame decreases, and changes of the temperature curve slow down. Nl < 1.0 Nl > 1.0 the temperature curve displays a dented tendency, though the changes are not very distinct. the temperature curve almost only displays linear changes regardless of any increase of the N 1 value. The observation of changes of Nl from 0.01 to 20(Figure 2(b» reveals that as N2 increases (i.e. the role of convection becomes more important), the temperature gradient closer to the flame increases, with very dramatic changes of the temperature curve. N 2 < 1.0 the temperature curve shows a slightly vaulted tendency, and changes little as a result of changes in Nl . the temperature curve shows iinear changes. the temperature shows a dented tendency, and the larger the N 2 value, the greater the dented curvature. Figure 2(c) indicates that as to increases (i.e. the preheat zone becomes thicker), the temperature gradient closer to the flame increases, with very dramatic changes of the temperature curve. to ~ 0.01 the temperature curve shows almost only linear changes, with limited changes to > 0.01 as a result of the changes of to . the temperature curve shows a dented tendency. In general, the curvature of temperature distribution increases as to . However, the opposite is true when to ranges between 3 and 4. Figure 2( d) indicates that the optical properties of medium particles exert an limited effect on the temperature profile in the preheat zone, with a dented and gradually increasing curve. 6 |