A DNS study of ignition characteristics of a lean iso-octane/air mixture under HCCI and SACI conditions

A Comparative Study of Conditional Moment Closure Modelling for Ignition of iso-octane and n-heptane in Thermally Stratified Mixtures

“…One DNS data-set modelled ignition of a lean n-heptane/air mixture with thermal stratifications in a constant volume [13] while the other modelled ignition of an iso-octane/air mixture in a similar configuration [14]. Both DNS databases were generated using S3D, a high order, fully explicit finite-difference solver which has been used for many studies [53][54][55][56][57][58][59].…”

“…However, as discussed in the literature, temperature fluctuations in HCCI engines have a magnitude about 25 K [5]. In these conditions gradients of ignition delay are believed to be insufficient to result in significant amounts of burning in premixed flames, at least away from walls, such that the predominant mode of combustion is a chemically controlled, spontaneous ignition [8,9,13,14]. As a result of the dominance of spontaneous ignition, the combustion process is mainly controlled by thermochemical state prior to ignition.…”

“…The effect of thermal stratification under HCCI conditions has been investigated using direct numerical simulation (DNS) for various fuels such as hydrogen [8][9][10][11], n-heptane [12,13], iso-octane [14] and dimethyl ether [15,16]. From some of these DNS studies, two combustion modes were found under HCCI conditions: deflagration and spontaneous ignition.…”

“…iso-octane/air mixtures [14], or there is only a weak two-stage ignition, i.e. n-heptane/air mixtures with the mean temperature of 1008 K [13].…”

A computationally-efficient, semi-implicit, iterative method for the time-integration of reacting flows with stiff chemistry

“…Heavier fuels have been considered in ignition simulations of HCCI-like systems (e.g. n-heptane [6], iso-octane [8], and ethanol [9]). The application of explicit time-integration methods are commonly limited by prohibitively small time step sizes to resolve the smallest chemical timescales present in the system (challenge #4) [27,40].…”