Effects of NOx-SOx Addition on Methane Ignition: Toward a Kinetic Understanding for Marine Engine Applications

Abstract

This paper presents a computational study of the effects of nitrogen and sulfur oxides doping on the ignition of methane-air mixtures under marine engine–like conditions. The performance of four detailed chemical kinetic mechanisms, appropriately coupled with nitrogen and sulfur chemistry reactions, is first assessed against literature experiments. An assembled mechanism is thus adopted and used to investigate NOx-SOx doping effects on the ignition of homogeneous methane mixtures for a wide variation of pressure, temperature, equivalence ratio, and doping concentrations. Extensive rate-of-production analysis is performed in order to delineate chemical effects on ignition. The present results confirm that, in general, the addition of either NO or NO2 reduces ignition delay time. NO2 is found to be more drastic than NO at intermediate pressure; this trend is milder at high pressure. The effects of SO2 on ignition chemistry are not significant. An outcome of the present study is thus an operating grid, relevant for controlling marine engine combustion. The assembled mechanism, subject to reduction, can be used in marine engine computational fluid dynamics (CFD) studies.