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PDF-equation approach have been extended and assessed for the diesel spray combustion computation. This approach accounts for the effects of gas turbulence and random dynamics of vaporizing liquid droplets on the chemistry. The combustion process including spray dynamics, evaporation, mixing and combustion have been treated using the combined KIVAII-PDF-equation model. Numerical computations were compared with the experimental data for spray self-ignition and combustion and with calculations using Eddy-Break-Up combustion model. Both the light-duty and heavy-duty diesel conditions have been operated in computations. Besides, the most probable self-ignition zone was computed and compared with experimental observation. It was showed that the developed here PDF model is abble to describe species concentrations, auto-ignition phenomenon and overall turbulent heat release significantly better than Eddy-Break-Up model.

A numerical submodel within the PDF-approach is developed for calculation of turbulent evaporation in liquid fuel sprays. This submodel is based on the Monte Carlo simulation of derived PDF transport equation for vapor concentration that accounts for both large scale turbulent air-fuel mixing and small scale turbulence. Evaporation-micromixing interaction is treated within coalescence-dispersion processes where evaporated mass is presented in statistical manner. The submodel is incorporated into KIVA II diesel spray codes. Computations of transient dynamics of vaporizing fuel spray were performed to assess the fluctuating structure of fuel vapor field. Discontinuous distributions of fuel vapor mass fraction are demonstrated in zones were droplets are still not evaporated. Highest intensity of vapor concentration fluctuations at the spray tip was observed.