Numerical study of effects of addition of coal particles on the characteristics of lean methane-air premixed flames

This study numerically investigates the effects of addition of micron-sized coal particles on the characteristics of lean methane-air premixed flames. Mass, momentum, species and energy conservation equations are solved in a two-dimensional axisymmetric domain. A short chemical kinetics mechanism for methane oxidation with 25 species and 121 reactions, temperature and species concentration dependent thermo-physical properties and an optically thin approximation based radiation model are incorporated. Discrete phase model (DPM) is used to analyze the transport of coal particles. Laminar flame speed has been calculated from numerical shadowgraph images using cone angle method. The variation in the flame speed due to injection of coal particles of different size ranges (1 - 25 microns, 50 - 60 microns and 75 - 90 microns) into lean mixture of methane-air flames (equivalence ratios of 0.75. 0.8 and 0.85) are presented. The predicted results have been validated against the experimental data available in literature. Based on the coal particle size range and equivalence ratio, the flame speed either increases or decreases. Results in terms of contours of temperature, species mass fraction, net reaction rate and DPM source are analyzed to explore the reasons behind the variation in laminar flame speed.