Low-Temperature Oxidation and Combustion of Stoichiometric NH3/C2H2/O2/Ar Mixtures at Atmospheric and Elevated Pressures

Ammonia is a promising fuel, the implementation of which could reduce carbon emissions into the atmosphere. However, to ensure the appropriate combustion characteristics of ammonia, additional technologies are required, since pure ammonia has poor combustion properties. One of them is to use a pilot fuel with high reactivity, for example, acetylene. Successful implementation of NH3/C2H2 mixtures requires a detailed understanding of the chemical processes taking place during their oxidation and combustion. At present, there are very few fundamental works focused on such systems. In this work, the experimental data on the oxidation of a stoichiometric NH3/C2H2/O2/Ar mixture in a jet-stirred reactor at atmospheric pressure, as well as on the chemical structure of stoichiometric NH3/C2H2/O2/Ar flames at 1–5 atm, are presented. The work also includes numerical modeling and analysis of NH3 and C2H2 consumption pathways at high and low temperatures, as well as at atmospheric and high pressure. Analysis of the consumption pathways shows that the first steps of oxidation of the fuel mixture components include reactions with the main radicals (H, O, and OH), while the contribution of cross reactions becomes noticeable only at later stages of ammonia and acetylene conversion. The main mechanism of ammonia–acetylene interaction during their oxidation and combustion is the coupling of their individual conversion processes, which involve reactions with H, O, and OH radicals. These radicals are common for both ammonia and acetylene oxidation.