Autoignition of methane/coal particle/air mixture under constant-volume conditions

Autoigniton of methane/air mixture loaded with uniform coal particles is simulated using the Eulerian-Lagrangian method. A zero-dimensional constant-volume approach is employed to investigate the impacts of particle diameter, particle concentration, and initial gas pressure on the two-phase mixture ignition process. Different stages are found from the ignition transient: particle heating, particle/gas thermal runaway, two-phase heat exchanges, and thermal quasi-equilibrium of two phases. Moreover, the igni-tion delay time of the two-phase mixture changes nonmonotonically with the particle size. Also, as the particle concentration increases, the magnitude of the differences in two-phase mixture ignition delays gradually decreases. At low particle concentrations, the particle temperature rises and then rapidly drops due to burnout of the fixed carbon, while the two-stage gas temperature increase is found. In addition, the two-phase mixture is more easily ignited under high pressure conditions. The particle ignition is more sensitive to pressure change than the gas ignition. An ignition diagram of methane/coal two-phase mixture with various particle concentrations, initial pressure and diameters is determined based on parametric studies. It is shown that particle addition promotes the gas ignition when the particles are small. Moreover, the particles can have inhibitory effects on gas ignition at high particle concentrations, and lower pressure. The results from this study are significant for explosion hazard mitigation implementations and detonation propulsion systems with pulverized solid fuels.(c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The autoignition of a methane/air mixture loaded with uniform coal particles is simulated using the Eulerian-Lagrangian method. The study investigates the impacts of particle diameter, particle concentration, and initial gas pressure on the ignition process of the two-phase mixture. The results show that the particle size has a nonmonotonic effect on the ignition delay time of the two-phase mixture, and the differences in ignition delays decrease as the particle concentration increases. Additionally, the two-phase mixture is more easily ignited under high pressure conditions, with the particle ignition being more sensitive to pressure change than the gas ignition. The findings of this study are significant for explosion hazard mitigation and propulsion systems with pulverized solid fuels.