A computational study on the quenching and near-limit propagation of smoldering combustion

Smoldering is the slow, low-temperature, and flameless burning of porous fuel and one of the most persistent types of combustion phenomena. The influence of cooling on the smoldering propagation and quenching is of practical significance but still poorly understood. In this work, a physics-based 2-D computational model that integrates heat and mass transfer and heterogeneous chemistry is built to investigate the limiting quenching conditions of in-depth smoldering propagation in a typical biomass sample. Simulation results predict that the smoldering quenching occurs as the sample width decreases or the wall-cooling coefficient increases, agreeing well with experiments. The modelled minimum smoldering temperature is about 350 °C, and the minimum propagation rate is around 0.5 cm/h. Further analysis demonstrates that either the smoldering temperature or propagation rate increases with the sample width and eventually approaches it maximum value. Finally, the influences of the ambient temperature and oxygen level on the smoldering quenching distance are explored. This is the first time to use a comprehensive physics-based model to predict the quenching behavior of smoldering, which provides a deeper understanding of the persistence and extinction limit of smoldering fire phenomena.