Experiment on fire spread and smoke characteristics in a narrow confined space
[Objective]Long-narrow confined spaces,while facilitating the mobility and daily lives of urban and rural residents,also pose fire safety concerns.Catastrophic combustion phenomena in such a space can result in significant casualties and property damage.Owing to the coupling effect of the long-narrow space and longitudinal ventilation,the fire plume and smoke layer behavior significantly differ from that of conventional buildings.Therefore,studying fire behavior and smoke spread characteristics under limited boundary conditions holds great scientific significance in thermal safety engineering.Research-oriented experimental teaching plays a crucial role in achieving the educational goals of fire engineering majors.Through scientific research-expanding experiments,students can consolidate and deepen their understanding of combustion science,fire dynamics,and smoke control engineering.It also improves students'independent analysis,problem-solving,comprehensive design,and innovation abilities.Furthermore,a trinity experimental teaching program was established to improve the practical teaching effect by integrating virtual entities,scientific research teaching,and theory experiments.This teaching approach involves conducting physical experiments to observe phenomena,record data,and analyze results.The virtual experiment establishes a virtual simulation scene to simulate the computational fluid dynamics of fluid motion in a fire,uses numerical methods to solve the NS equation of low Mach number flow driven by fire buoyancy,and observes the dynamic flow field parameters through the field simulation results.Building a full-scale test platform for fire science research considering the unique characteristics and high aspect ratio of a long-narrow confined space is difficult.Therefore,downscale experiments are commonly used because of their convenience and cost-effectiveness.[Methods]In this paper,a medium-scale experimental platform is selected for the experimental teaching program.Using a medium-sized experimental platform,the overall arrangement of physical experiments is based on experimental design,system construction,experimental operation,and teaching results.The characteristics of the fire plumes,flame propagation rates,and distribution patterns of fire smoke temperature were investigated.Using PyroSim to establish virtual simulation scenarios,FDS for simulation calculations,and field simulation diagrams to record experimental teaching results,we could perceive the dynamic process of fire occurrence and development.We also analyzed experimental results,such as temperature,velocity vector,and smoke concentration.[Results]The following findings were observed:①under longitudinal ventilation conditions,owing to forced convection or buoyancy-induced natural convection,the flame inclines downstream,and the inclination angle increases with the increase in ventilation velocity.②Higher wind speeds result in fast changes in the position of the pyrolysis front,increasing flame propagation rates.③An increase in wind speed facilitates the expulsion of hot smoke,and the temperature changes with the flow of hot smoke.④Temperature differences are observed on both sides of the fire source under the influence of ventilation,and the temperature on the downwind side decreases as the distance from the fire source increases.⑤The wind speed in the smoke backflow region was lower than in other areas.Combustion science,fire dynamics,and smoke control engineering are the core subjects of the fire protection engineering undergraduate program.Owing to classroom instruction constraints,students'understanding of the subject matter is primarily theoretical.However,a three-dimensional understanding of the theoretical concepts can be gained when combined with experiments.This experimental teaching content enhances students'comprehensive abilities to analyze and solve problems during the experimental process,effectively shaping their innovative and practical capabilities.
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