Abstract
The previously suggested quasi-discrete model for heating and evaporation of complex multi-component hydrocarbon fuel droplets is described. The dependence of density, viscosity, heat capacity and thermal conductivity of liquid components on carbon numbers n and temperatures is taken into account. The effects of temperature gradient and quasi-component diffusion inside droplets are taken into account. The analysis is based on the Effective Thermal Conductivity/Effective Diffusivity (ETC/ED) model. This model is applied to the analysis of Diesel and gasoline fuel droplet heating and evaporation. The components with relatively close n are replaced by quasi-components with properties calculated as average properties of the a priori defined groups of actual components. Thus the analysis of the heating and evaporation of droplets consisting of many components is replaced with the analysis of the heating and evaporation of droplets consisting of relatively few quasi-components. It is demonstrated that for Diesel and gasoline fuel droplets the predictions of the model based on five quasi-components are almost indistinguishable from the predictions of the model based on twenty quasi-components for Diesel fuel droplets and are very close to the predictions of the model based on thirteen quasi-components for gasoline fuel droplets. It is recommended that in the cases of both Diesel and gasoline spray combustion modelling, the analysis of droplet heating and evaporation is based on as little as five quasi-components.
Highlights
In a number of our earlier papers it was demonstrated that the choice of the model for droplet heating and evaporation leads to a noticeable effect on the predicted autoignition delay in Diesel fuel sprays [1, 2]
The dependence of density, viscosity, heat capacity and thermal conductivity of liquid components on carbon numbers and temperatures is taken into account
This model is applied to the modelling of Diesel and gasoline fuel droplet heating and evaporation
Summary
In a number of our earlier papers it was demonstrated that the choice of the model for droplet heating and evaporation leads to a noticeable effect on the predicted autoignition delay in Diesel fuel sprays [1, 2]. As follows from (5), (7) and the results for liquid density, viscosity, specific heat capacity and thermal conductivity, the transport and thermodynamic properties of the fuel components are relatively weak functions of n. In this case, following [18, 19], it would be sensible to assume that the properties of hydrocarbons in a certain narrow range of n are close, and replace the continuous distribution (3) with a discrete one, consisting of Nf quasi-components with carbon numbers nj =. Having replaced n with nj we obtain the required values of psat, L, liquid density, viscosity, specific heat capacity and thermal conductivity for all quasi-components. The difference between them, is expected to be relatively small and will be ignored in our analysis
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