The Influence of Nitric Oxide on the Occurrence of Autoignition in the End Gas of Spark Ignition Engines

Full cycle simulations of a spark ignition engine running on a primary reference fuel have been performed using a two-zone model. A detailed kinetic mechanism is taken into account in each of the zones, while the propagating flame front is calculated from a Wiebe function. The initial conditions for the unburned gas zone were calculated as a mixture of fresh gas and rest gas. The composition of the burned gas zone at the end of the last engine cycle, including nitric oxide emissions, was taken as rest gas.

The simulations confirm that the occurrence of autoignition in the end gas is sensitive on the amount of nitric oxide in the rest gas of the spark ignition engine. The comparison of autoignition timings calculated for a single cylinder test engine are getting more accurate if the nitric oxide in the initial gases is taken into account.