Numerical Simulation of Fire in Underground Commercial Street.

In this study, while aiming at the prevention of fire accidents in underground commercial streets, an underground commercial street is selected as a research object, and the building fire is numerically simulated using the PyroSim software. Fire simulation scenarios are divided according to different fire zones by analyzing the temperature, carbon monoxide (CO) concentration, and visibility in the smoke layer inside a building. The available safe evacuation time is calculated according to the critical fire hazard judgment conditions. We found that the time when the flue gas temperature and CO concentration reached the critical value in the fire site was longer than the time when the visibility reached the critical value reducing or even avoiding the spread of smoke from the fire area to the evacuation stairs can provide effective help for crowd evacuation. Finally, the safety of the building is evaluated, and fire prevention countermeasures are defined based on the actual situation and fire numerical simulation results to reduce fire incidence, casualties, and economic losses.

Analysis of Frank-Kamenetskii thermal explosion system of non-class a geometry based on Boltzmann method.

Exothermic reaction systems of non-class A geometries are very common, with an endless rectangular rod typical. As a strong nonlinear source word is included in the governing equation, which is sensitive to the frank-kamenetskii parameter, there is no analytical solution. Many methods were previously suggested. However, with them are often non-physical solutions obtained. In this paper, the lattice Boltzmann process provides us with complete physical and precise solutions. We also analysed the sensitivity of the strong nonlinear source term and suggested advice for similar numerical calculations and experiments with thermal explosion.

[The microstructure and phase composition of metal melting marks caused by different fire].

Four different types of molten metal fire marks were studied through X-ray diffraction (XRD) and 3D image processing software (Image-pro). As a result, the microstructure, average grain size, phase composition and its distribution was obtained. The results showed that on the surface of molten metal fire marks there mainly existed cubic crystal of Cu2O, cellular crystals of Cu and columnar crystals of Cu. And in four different modes of fire, the microstructure and composition of molten metal marks was of significant difference, that is: (1) the average grain size of molten marks by a short circuit fire was about 3 - 5 microm, and its Cu2O was the lowest; melt marks by circuit overload had an average grain size similar to short-circuit, but their Cu2O content was about 30%; (2) melt marks by secondary short-circuit contained a certain number of larger diameter microhole, and their average grain size was about 30 microm; broadening and splitting provision of the diffraction peaks of Cu and Cu2O showed that their ablation was the deepest; (3) melting marks by fire showed the equiaxed maximum intensity of Cu2O diffraction peaks, and there was almost no micro-holes.