Analysis of the Influence of Droplet Breakup Time using Kelvin-Helmholtz Model, on the Diesel Spray Formation, Evaporation and Combustion

Abstract

A numerical simulation of the intake and compression stroke and fuel spray and combustion in a direct injection compression ignition engine was performed using the Converge CFD software. For this purpose, the Reynolds Average Navier-Stokes (RANS) k-e RNG model and an n-dodecane kinetic mechanism were used in order to obtain the flow fields in the cylinder and to perform the breakup time analysis of the Kelvin-Helmholtz model in the variables related to the spray and combustion. The turbulent flow inside the cylinder was analysed, obtaining consistent results with experimental pressure data and other research authors. The droplet breakup time is evaluated as a function of the breakup time constant (B1), the initial droplet radius (r_o), the wavelength  and the maximum growth rate ( . The results indicate that the numerical method and the models used in this work are adequate to perform subsequent representative combustion analyses with values of B1=7.  It was possible to show that the formation of the species OH is greater for low values of B1. Also, higher values of the breakup time, variables such as temperature, pressure, fuel evaporation, ignition delay, and species formation are affected.