High-Pressure Spray and Combustion Modeling Using Continuous Thermodynamics for Diesel Fuels 2001-01-0998
Practical diesel fuel sprays under high-pressure conditions were investigated by using multidimensional modeling combined with continuous thermodynamics and high-pressure multicomponent fuel vaporization models. Transport equations, which are general for the moments of the distributions and independent of the distribution function, are derived for the continuous system consisting of the both gas and liquid phases. A general treatment of the vapor-liquid equilibrium (VLE) is conducted, and the Peng-Robinson Equation of State (EOS) is used to find the surface equilibrium composition. Relations for the properties of the continuous species are formulated. The KH-RT model is used for spray breakup prediction. The fuel droplets are assumed to be well mixed with uniform temperature and composition within each droplet. The turbulent flow field is calculated using the RNG k -ε turbulence model.
The model predicts liquid lengths in vaporizing sprays that compare favorably with available experimental data. The model was also applied to practical engine simulations. The ignition model is a modified Shell model that accounts for multicomponent fuel effects on the Cetane number. Combustion is modeled with a laminar-turbulent characteristic time combustion model. Numerical results for No. 2 diesel fuel are presented with comparison to low-pressure model predictions. The results clarify the characteristics of engine fuel sprays and indicate that it is important to consider high-pressure multicomponent fuel vaporization effects in engine calculations.