This study addresses the significant fire hazards associated with using thermoplastic materials, particularly PMMA (poly methyl methacrylate), which are prone to flammability and high calorific values. By employing a methodology that combines small-scale experiments and theoretical analysis, this paper investigates the impact of material width on the behavior of discrete flames in open spaces, using specimens ranging from 5 to 10 cm in width. The findings indicate that an increase in specimen width positively affects the burning area and brightness, while the dimensionless flame height and heat release rate per unit width exhibit a negative power law decay with increasing width. This suggests that beyond a critical width, further increases in width have little influence on flame propagation. The results of this study contribute to a better understanding of fire dynamics in thermoplastics and provide valuable insights that could lead to enhanced fire safety standards and material designs. The originality of this research lies in its detailed analysis of how material dimensions influence flame behavior, a topic that has not been extensively explored before, offering significant practical value in applications where fire safety is crucial.

With the increase of fire in high-rise buildings in recent years, the demand for high-performance Water Tower Fire Truck (WTFT) is increasing day by day. In order to improve the injection capacity of ultrafine dry powder of the WTFT, this article adopts the way of adding blow-assisted pipe to realize nitrogen-assisted blowing, and the internal flow field of existing blow-assisted pipe was analyzed and optimized by CFD simulation. The influence law of size parameters on the mass flow rate and velocity of ultrafine dry powder and nitrogen was analyzed and summarized under different inlet pressure conditions. The optimization result is that the diameter of the nitrogen-assisted blowing pipe is increased between 10 mm and 20 mm, the diameter of the outlet pipe is 32 mm, and the diameter of the inlet of the mixing pipe is 90 mm.

To understand the early warning signs of damage during the coal mass deformation process, an integrated monitoring procedure was designed that combines the apparent resistivity (AR) and acoustic emission (AE) of coal damage under multi-step loading. The spatiotemporal response characteristics of AR and the time-varying evolution of AE were studied and the varying correlation between the two was discussed. Additionally, the macro–microscopic mechanics of the AR response during the coal deformation process was explored. The results show that the AR and AE signals corresponded well with the applied load during the coal deformation process. In the early loading stage, variations in AR and AE signals were not apparent. As the applied load increased, the high-resistance area of AR increased and the AE signals became active. The local variation characteristics of AR could be used to indirectly invert the internal structure of the coal samples. The electrical variation in the loaded coal was mainly controlled by the conductive surface of cracks. The acoustic and resistivity methods can strongly complement the spatial and temporal dimensions of early warning systems for disasters. The AE technique can continuously monitor a test area for abnormal occurrences in the engineering site, and AR tomography images that are obtained can be used to locate inversions in the source coal in order to take pre-emptive action before disaster occurs. This research can provide new ideas for monitoring and early warning systems for coal and rock dynamic disasters.