Study on effect of dimethyl ether addition on combustion characteristics of turbulent methane/air jet diffusion flame

Abstract

The kinetics and soot and NOx emission characteristics of the CH4/dimethyl ether (DME) jet diffusion flames (JDFs) are studied by experiments and simulations with a detailed chemical mechanism. The results showed that decomposition of DME in the pyrolysis zone generated massive CH3, which changed the local flame structure and soot-correlated chemistry to some extent. Due to reductions of the incipient species concentrations including benzene (A1), pyrene (A4), C3H3, and C2H2, soot loading of the CH4 JDF decreased by reducing margins with DME addition. A1 and thus soot formation rates due to DME addition were most sensitive to the recombination reaction of C3H3 (C3H3+C3H3=A1). With respect to the CH4/DME JDFs, NOx was emitted mainly through the thermal and prompt pathways. The thermally-generated EINOx increased exponentially with DME addition because of the increasing enhancement of OH concentration in the radical pool. By contrast, the promptly-generated EINOx decreased in reducing margins with DME addition because of the reducing decrease in CH concentration. The synergistic effect of DME addition on the total NOx emission, i.e. the overall EINOx decreased firstly and then increased with DME addition, was examined in this paper. Additionally, it is reported that the 40%CH4/60%DME case was comprehensively optimal in terms of soot and NOx emission reductions.