During the combustion of low-concentration coal mine methane in a porous medium, subadiabatic combustion
will occur with the upstream propagation of combustion waves. The lower concentration limit of
methane combustion can be broadened, when the porous medium skeleton is preheated by the upstream
propagation of combustion waves. In this study, an experimental apparatus of porous medium combustion
was built and used to validate a numerical model. Then numerical tests were conducted to characterize
the upstream propagation of combustion waves, and investigate the effects of many factors (e.g.
methane working conditions, heat loss through walls, and dispersion effect) on the propagation.
Results show that the upstream propagation of combustion waves is kept at an even velocity. During
the propagation, the combustion products temperature at the burner outlet gradually decreases, while
the peak temperature is unchanged. With the increase of methane concentration, the upstream propagation
velocity of combustion waves and the peak temperature both increase. As the inlet gas velocity is
increased, the upstream propagation velocity decreases but the peak temperature raises. As the heat loss
through walls is increased, the upstream propagation velocity and the peak temperature both decrease.
The CO emission quantity gradually decreases during the upstream propagation of combustion waves.
With the increase of inlet velocity and heat loss through walls, the CO emission quantity within the same
propagation period gradually increases. The NO emission quantity first increases slowly and then stabilizes
during the upstream propagation of combustion waves. Moreover, with the increase of inlet velocity
and decrease of heat loss through walls, the NO emission quantity within the same propagation period
increases.