Numerical study of methane mixtures' conversion under the influence of laser radiation

The article presents a study of methane mixtures' laser conversion under various conditions of the computational experiment. Such flows are characterized by sharp local changes in the gas dynamic characteristics and the mixture components' concentrations. Their dynamics and mutual transformations are described by a stiff system of Navier-Stokes equations and chemical kinetics, which imposes serious restrictions on the choice of a computational algorithm. Numerical experiments were carried out using previously developed 2D code for modeling subsonic axisymmetric flows of a multicomponent medium, supplemented by modules that take into account laser radiation and solve equations of methane conversion's chemical kinetics. Verification of the results was made by calculating the conversion of methane under the influence of walls' external heating. Comparison of the substances' concentrations at the pipe outlet with the direct solution of the chemical kinetics system at different reaction temperatures showed a good agreement of the results. Computational experiments on the laser radiation's effect on the flow of a chemically active absorbing medium have been completed. It is shown that the laser radiation introduced into the mixture and absorbed by ethylene, changes the flow pattern and significantly increases the temperature of the gas mixture. An increase in temperature contributes to an increase in the yield of target products (ethylene, acetylene, hydrogen) at the reactor shorter length, while in the absence of radiation, the maximum concentrations of products appear at the reactor's outlet. The effect of the initial composition of the gas mixture on the methane's conversion is investigated, and it is concluded that the presence of ethylene significantly increases the formation of target products at moderate reactor walls' temperatures in the presence of laser radiation.