2-D SIMULATION OF TURBULENT AUTOIGNITION WITH TRANSIENT LAMINAR FLAMELET SOURCE-TERM CLOSURE

The motivation for the present study is the attempt to enhance the und erstanding of the influence of inhomogeneous turbulence influence upon autoignition processes, which are of interest for practical applicati ons such as the Diesel engine. Special attention is paid to the modell ing of chemical source term closure and its coupling with inhomogeneou s turbulence. Detailed two-dimensional simulations of turbulent autoig nition with flamelet source term closure have been performed using a l aminar flamelet presumed pdf model (pdf = probability density function ). The transient autoignition calculations of the laminar flamelet are based on a reduced 4-step chemical kinetic mechanism of heptane combu stion in air. New ways of modelling turbulent chemical source term clo sure are investigated. Specifically, an ignition time variable is intr oduced to characterize the aspect of transient chemical reaction durin g the turbulent autoignition process. The model successfully covers th e period from early autoignition to flame propagation.