Turbulent flame propagation limits in polymethylmethacrylate particle cloud combustion

From the perspective of energy generation and fire protection, the combustion of solid particle clouds has been studied for many years. However, limited research has been undertaken to clarify turbulent flame propagation and extinction phenomena and mechanisms in solid particle cloud combustion. To the best of our knowledge, this paper is the first to report on turbulent flame extinction limits and associated mechanisms governing turbulent flame propagation and extinction in pure solid particle cloud combustion. In this work, experiments on turbulent flame propagation limits during quasi-monodispersed polymethylmethacrylate (PMMA) particle cloud combustion were conducted using a custom-designed fan-stirred constant-volume chamber operating under ambient air conditions. The results demonstrate that the turbulent flame propagation limits during pure solid particle cloud combustion were expanded with increasing particle concentration, independent of particle size for low particle cloud concentrations. Nevertheless, at high particle cloud concentrations, the limits were minimally influenced by the particle concentration and expanded with a reduction in particle size. The trend of the turbulent flame propagation velocity was consistent with our earlier studies involving coal particle clouds (Hadi et al., 2019) [12] and PMMA particle clouds (Xia et al., 2021) [7] in oxygen-enriched conditions. This suggests that turbulent flame propagation velocity is minimally influenced by particle concentration and tends to increase with decreasing particle size. An analysis was conducted to replicate the experimental trends observed in the turbulent flame propagation velocity. The findings underscore the significance of turbulent heat and mass transfer, and particle devolatilization behavior in governing turbulent flame propagation and extinction during pure solid particle cloud combustion. The outcomes of this study can assist in the design and operation of burners for combustion of solid particle fuels, the formulation of fire protection strategies to prevent particle cloud explosions, and the development of new theoretical models for the turbulent combustion of solid particle clouds.