The 'extended' and 'effective-conductivity' models of droplet vaporization developed by Abramzon and Sirig-nano are generalized to take into account the contribution of thermal radiation and the temperature dependence of liquid fuel properties. In the first model, the convection of liquid is explicitly taken into account, while in the second model the effect of liquid convection on the droplet surface temperature is accounted for by replacing the actual thermal conductivity of liquid by the so called 'effective thermal conductivity'. In both models the contribution of thermal radiation is taken into account based on the simplified model for thermal radiation absorption suggested by Dombrovsky and Sazhin. This model is based on the geometric optics and the MDP_0 approximations, and allows a rather simple description of temperature distribution inside the droplet. Physical properties of diesel fuel are approximated by those for n-dodecane. It is pointed out that the radiation absorption in diesel fuel is generally stronger than in n-decane, and it needs to be taken into account in modeling the combustion processes in diesel engines. Weak effect of thermal radiation in n-decane droplets, however, may be related to the fact that due to lack of experimental data, absorption coefficient was assumed to be zero at λ < 2.6 μm. When data were available, the absorption of radiation of n-decane was generally less than that of diesel fuel especially in the regions of semi-transparency (λ not close to 3.4 μm). Comparison between the calculations performed using the 'extended vaporization' model and distributed radiation absorption heat source and those based on the 'effective-conductivity' model with the uniform distribution of the internal heat source show exceptionally good agreement between the results. This allows us to recommend using the 'effective-conductivity' model with uniform radiation absorption for spray combustion calculations, including the applications in diesel engines.
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