PDF MODELING 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, liq uid n-heptane is injected into a quiescent, hot, high-pressure environ ment of air. A hybrid approach to the simulation of this problem is ad opted, where the Favre-averaged gasphase equations governing conservat ion of overall mass, momentum and turbulence are discretised using a f inite-volume method. The statistics of the two-phase how are described by a marginal gasphase pdf for a mixture fraction and a reaction-prog ress variable. which obeys the scalar pdf-transport equation usually u sed to model purely gaseous turbulent flames, and a marginal liquid-ph ase pdf, the so-called ''spray equation''. The Eulerian gasphase conse rvation equations are solved by a predictor-corrector pressure implici t method to provide quantitative information concerning the evolving m ean turbulent flow field. The transport equation of the gasphase-scale r joint-pdf is solved using a Monte Carlo method. The spray equation i s solved using a Lagrangian formulaiton in conjunction with another Mo nte Carlo method. Good agreement is found between the results predicte d herein and experimental data reported in the literature.