Experiments of premixed syngas/air explosion inside parallel narrow channels were conducted. The flame propagation, explosion pressure and temperature inside the narrow channel are investigated to find out the effect of narrow channel spacing on the explosion. The experimental results show that the narrow channel spacing has an influence on the flame before and inside the parallel narrow channels. The flame inside the narrow channels accelerates and reaches a peak value at the middle or rear of the channel. The flame front velocity, the maximum explosion P_max and the maximum explosion flame temperature T_max decrease as the channel spacing decreases. The channel wall has an effect of heat dissipation on the flame, resulting in the explosion inside the channel weakening. The explosion pressure in rear of the narrow channel is larger than that in the front of the narrow channel.

The characteristics of methane-air explosion in interconnected containers with different dimensions are studied in this paper, and the prediction models are established. The explosion apparatus consists of two cylindrical containers and a connecting pipe, and three structure parameters are selected as influencing factors for the experiments. The explosion pressure, the maximum rate of pressure rise and pressure growth index under different conditions are compared by changing the volume ratio (V₁/V₂), the length of the pipe, and the inner diameter of the pipe. During the experiment, the combustion and explosion of gas developed from the main container to the auxiliary container. Under different size effect conditions, the maximum explosion pressure in the secondary container was always higher than the maximum explosion pressure in the primary container. The maximum explosion pressure and the maximum rate of pressure rise in the primary and secondary containers both increase with increasing pipe length. With an increase in the pipe diameter, the maximum explosion pressure and the maximum rate of pressure rise both decrease gradually. When the volume ratio changes, the parameters such as the maximum explosion pressure are also affected by the volume changes of the containers at both ends. Therefore, the explosion parameters in both connected containers do not show a single development trend with the increase of the volume ratio. For practical application, in order to reduce the explosion intensity and protect the device, large-diameter pipes should be used and the volume ratio should be reduced.

Hydrogen has been recently utilized in many fields due to its recyclability and non-pollution characteristics. Hydrogen fuel cell vehicles and hydrogen refueling stations have become the main carrier of hydrogen energy application. However, due to the inflammable and explosive characteristics, the safety problems of hydrogen became indispensable. This paper introduces the safety problems and countermeasures of hydrogen fuel cell vehicles and hydrogen refueling stations. The research progress and achievements of hydrogen energy standards are then comprehensively discussed. Finally, the development status, existing problems and future development direction of five kinds of optical fiber sensors are pointed out.

Building exit has always been an emphasis of research in the field of evacuation. Existing studies on crowd flow characteristics at building evacuation bottlenecks usually focus on plane exit, but insufficient attention has been paid to the characteristics of crowd flow at the convex exit. Convex exit can be considered as such a structure like a double-bottleneck linked passage. This paper aims to study the influence of geometric structure characteristics of the convex exit on crowd evacuation and put forward the optimal design strategy of this structure, so as to improve the efficiency of evacuation in an emergency. Using social force model-based software, MassMotion, it is found that convex exit is indeed more efficient and safer than common plane exit in terms of evacuation time and pedestrians' congestion, especially when the desired speed is relatively higher, indicating that convex exits are more suitable for crowd evacuation in case of emergency. Four size-related parameters of convex exit are analyzed in detail, namely the width of the bottleneck at passage (W_p), the passage width (W), the passage length (L), and the exit width (W_e), to find out the optimum design of convex exit. The research shows that the optimal size ratio is that W_p: W: L: W_e equals 1.5:1.75:3.5:1, and as the overall magnification of building size and the number of pedestrians increases, the evacuation time gradually tends to a stable value, which indicates that this optimal ratio has good adaptability in size effect. Finally, based on the in-depth mechanism of pedestrian flow at the convex exit, three possible application scenarios are proposed to illustrate the feasible optimum design of the convex exit. The results of this study can provide new ideas for research on the structure of building exits.

In dense crowd evacuation, especially in emergencies such as fires, the safe evacuation of large public facilities will face major challenges. At the same time, as cluster congestion tends to occur in the space where the flow rate drops sharply, the superposition of fire incidents and bottleneck areas can easily evolve into malignant disasters and crowd stampedes with serious harm and influence. In this paper, Massmotion based on social force model is used to carry out a numerical simulation on exit position and corner exit form to find out the mechanism and influence law of the slight architectural adjustment on the flow at bottleneck. The results show that the traditional middle exit design is not the best, and the evacuation efficiency of the corner exit is higher than that of the middle exit. Compared with other corner exits, the average time interval between two adjacent persons passing through the bottleneck under the 30° corner exit is the shortest, and the probability of outlet clogging drops the fastest, exceeding 18% of the slowest descending speed. At the 0° corner exit, the waiting time cost of pedestrians is high and the risk of evacuation is high. The outcomes of this work can provide reference for the structural design of the building and the safe evacuation of personnel, so as to improve the evacuation efficiency and safety of pedestrians in the building to some extent.