Numerical simulation of CO generation and migration patterns in goaf based on coupled multi-physics fields

To explore early prediction methods for goaf spontaneous combustion, a numerical simulation was conducted to investigate the generation and migration laws of indicator gases in the goaf. A multi-physics coupling model integrating flow field, temperature field and concentration field was adopted to systematically analyze the spatio-temporal evolution of the temperature field and indicator gases. Programmed heating experiments revealed that CO exhibits a good correlation with temperature at low stages. Accordingly, CO was determined as the indicator gas in the numerical simulation, and the oxygen consumption rate, CO generation rate and heat release intensity were obtained. The multi-physics coupling results demonstrate that thermal buoyancy is the dominant driving force controlling the vertical migration and spatial distribution of CO in the goaf. Under the combined effect of air leakage and thermal buoyancy, CO accumulates in the upper, deep and return side regions of the goaf, which should be prioritized for monitoring. The findings provide important theoretical and engineering support for the prevention and control of goaf spontaneous combustion.