PDF modelling of spray autoignition in high pressure turbulent flows

This paper presents a computational study of spray autoignition under conditions similar to those found in Diesel engines. Specifically, liquid n-heptane is injected into a quiescent, hot, high-pressure environment of air. A hybrid approach to the simulation of this problem is adopted, where the Favre-averaged gasphase equations governing conservation of overall mass, momentum and turbulence are discretised using a finite-volume method. The statistics of the two-phase how are described by a marginal gasphase pdf for a mixture fraction and a reaction-progress variable. which obeys the scalar pdf-transport equation usually used to model purely gaseous turbulent flames, and a marginal liquid-phase pdf, the so-called ''spray equation''. The Eulerian gasphase conservation equations are solved by a predictor-corrector pressure implicit method to provide quantitative information concerning the evolving mean turbulent flow field. The transport equation of the gasphase-scaler joint-pdf is solved using a Monte Carlo method. The spray equation is solved using a Lagrangian formulaiton in conjunction with another Monte Carlo method. Good agreement is found between the results predicted herein and experimental data reported in the literature.