Effect of a palladium catalyst and initial pressure on methane-air catalytic combustion process in a helical coil microchannel: A molecular dynamics approach

Abstract

Catalytic combustion is a flame-free process which occurs at low temperatures and reduces less release of nitric oxide (NOx). Although catalysts help reduce the release of toxic gases, they have detrimental environmental effects. Therefore, by simulation these reactions, a constraint on the flammability limits and improving their performance can be achieved. In this research, using the molecular dynamics (MD) simulation, the catalytic combustion process of air-methane was studied in a helical microchannel. Palladium (Pd) was used as the catalyst. The results show that adding a Pd catalyst further improved the simulated structure's thermal performance(TP). The heat flux(HF) and thermal conductivity (TC) of atomic samples increased from 2067 W/m2 and 1.28 W/m.K to 2096 W/m2 and 1.45 W/m.K with an increase in atomic ratio Pd catalyst from 1 to 4%. Finally, the combustion efficiency (CE) converges to 93% in the presence of 4% Pd catalysts. By increasing the initial pressure (IP) from 0 to 10 bar, the maximum density did not change much, and the velocity and temperature values decrease in terms of the limitation in atomic oscillations. Increasing the IP reduces the HF and TC from 2096 W/m2 and 1.45 W/m.K to 1981 W/m2 and 1.19 W/m.K. Regarding different types of combustion processes, such as catalytic combustion, were considered in different types of industrial applications, it is expected to study the effect of the parameters of the atomic ratio of Pd catalyst and the IP, propose an optimal mechanism to create catalytic combustion in real and practical samples.