A direct numerical simulation of a turbulent, self-igniting temporal mixing layer between n-dodecane and diluted air has been conducted to clarify certain aspects of diesel engine combustion. The thermodynamics conditions were selected to result in a two-stage ignition event, in which low- and high-temperature chemical reactions play an equally important role during the ignition process. Jet parameters were tuned to yield a target ignition Damkohler number of 0.4, a value representative of conditions found in diesel spray flames. Chemical reactions were described by a 35-species reduced mechanism, including both the low- and high-temperature reaction pathways of n-dodecane. The present work focuses on the influence of low-temperature chemistry on the overall ignition transient. Previous studies have demonstrated that ignition is most likely to occur in those regions where scalar dissipation is low and the mixture composition is close to the most reactive one, e.g. the composition for which, in an homogeneous reactor, the ignition delay is the shortest. We investigate whether this picture still holds when low-temperature reactions are important, and how the ignition delay and location are affected by low-temperature chemical reactions.
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