Ignition in compositionally and thermally stratified n-heptane/air mixtures: A direct numerical simulation study

Abstract

This paper presents a direct numerical simulation (DNS) study of ignition characteristics in compositionally and thermally stratified n-heptane/air mixtures, relevant to homogeneous charge compression ignition (HCCI) engines. Nine two-dimensional constant volume cases are simulated. For each of three different mean temperatures, all within the negative temperature coefficient (NTC) region, three cases having different levels of mixture stratification are considered. Local temperature fluctuations, negatively correlated with mixture fraction fluctuations are also considered. It is shown that as the level of stratification increases, the heat release rate has a lower peak in the first stage fo..