THREE-DIMENSIONAL MODELING OF SELF-IGNITION IN HCCI AND CONVENTIONAL DIESEL ENGINES

Abstract

This paper addresses the problem of self-ignition modeling of diesel-related fuels in the framework of engine combustion three-dimensional computational fluid dynamics simulations. A model based on the evolution of a self-ignition progress variable is proposed and implemented in the KMB code. The evolution of the progress variable is determined cell by cell and is a function of a local self-ignition delay that depends on the cell fresh mixture thermodynamic conditions. These are temperature, pressure, equivalence ratio, and residual gas percentage. The local delays are calculated via interpolation inside an extensive ignition delay database created a priori. Each delay in the database is determined through complex chemistry calculations using SENKIN along with a kinetic mechanism from the literature developed for self-ignition modeling of n-heptane. The mechanism has been validated over a broad range of thermodynamic conditions. The ignition database covers the cold flame regime allowing application of the model to homogeneous charge compression ignition (HCCI) combustion. The model is validated through a series of tests including constant-volume self-ignition and homogeneous adiabatic compressed charge self-ignition. Results of the model are finally compared to experimental data of HCCI combustion as well as conventional diesel engine combustion with early pilot injection where cold flame self-ignition is a first-order phenomenon. The comparisons show the feasibility and accuracy of the model in computing industrial configurations.

Keywords:

• self-ignition modelling
• HCCI engines

This research was partially funded by the Groupement Scientifique Moteur, with PSA Peugeot Citroen, Renault SA, and IFP. The author would like to thank E. Delaunay, C. Morazin, and V. Knop, who helped on the database generation and model validation, as well as Dr. Curran and Dr. Westbrook for their help in obtaining the n-heptane mechanism.