Numerical investigation of the hybrid pulse–DC plasma assisted ignition and NOx emission of NH3/N2

The ignition delay and NO emission characteristics of the NH3/N2/O2 mixture under the influence of pulse–DC hybrid plasma discharges have been studied. The plasma and combustion chemistry mechanisms for NH3/N2/O2 mixture are reviewed, an improved kinetics mechanism is proposed with a well validated electron scattering cross section data. An improved coupled plasma and combustion chemistry code allowing sensitivity/pathway analysis is developed. The role of key species on the ignition delay time and the effects of low E/N discharge over long periods of time (DC stage) on NOx emission are studied. The results show that, NO emission will be strongly enhanced due to the increased HNO, NH and N density in NH3 containing mixtures in the DC stage, NO density increases with the E/N value in DC stage due to the reduction of NH and NH2 species. The role of O2(a1Δg) in promoting ignition was studied using different rate constant of O2(a1Δg)+NO→O2+NO: O2(a1Δg) mainly reacts with H2 and H to produce radicals such as O, H and OH instead of quenched by NO. The vibrationally excited NH3(v2) molecule plays the dominating role in heat release through V–T relaxation with NH3.