Numerical modeling of ignition enhancement using repetitive nanosecond discharge in a hydrogen/air mixture I: calculations assuming homogeneous ignition

Abstract

Abstract Ignition enhancement using repetitive nanosecond discharge (NSD) is studied in a stoichiometric hydrogen/air mixture. Numerical simulations are conducted for the homogeneous ignition process using code incorporating ZDPlasKin and CHEMKIN. The objective is to examine how the characteristics of the NSD affects the ignition delay time and why the NSD promotes a homogeneous ignition process. The influence of pulse number, discharge frequency, reduced electric field, total input energy and input energy per pulse on the ignition process is investigated. It is found that the characteristics of NSD have a significant impact on the ignition delay time. The ignition delay time changes non-monotonically with the reduced electric field, and it depends on both the total input energy and the input energy per pulse. Furthermore, it is shown that the ignition enhancement by NSD is mainly due to the kinetic effects while the thermal effects (Joule heat) are negligible. The ignition enhancement is mainly caused by radicals, especially H and O, produced by NSD. A reaction pathway analysis is conducted to identify the key elementary reactions involved in the ignition enhancement using NSD. The electron impact reactions and quenching reactions of excited species are found to help to produce H and O radicals and thereby promote the homogeneous ignition process.