Multi-dimensional modeling of natural gas autoignition using detailed chemical kinetics

The autoignition of natural gas injected into a combustion bomb at pressure s and temperatures typical of top-dead-center conditions in compression ign ition engines is studied by combining a detailed chemical kinetic mechanism , consisting of 22 species and 104 elementary reactions, with a multi-dimen sional reactive flow code. The effect of natural gas composition. ambient d ensity and temperature on the ignition process is studied by performing, ca lculations for three different blends of natural gas on a three-dimensional computational grid. The predictions of ignition delay compare very well wi th measurements in a combustion bomb. Based on this work, it is established that a particular mass of fuel burned is a much better criterion to define the ignition delay period than a specified pressure rise. The effect of ad ditives like ethane and hydrogen peroxide in increasing the fuel consumptio n rate as well as the influence of physical parameters like fuel injection rate and intake temperature is studied. It is thus shown that apart from ac curate predictions of ignition delay. the coupling between multi-dimensiona l flow and multi-step chemistry is essential to reveal detailed features of the ignition process.