Research On Influence Of Moving Fire On Temperature Field Distribution And Smoke Spread In Tunnel

Tunnel space is long, narrow and nearly airtight. Once fire occurs inside, heat flux ofhigh temperature and smoke will greatly threaten tunnel structure and lives of people involved,and moving vehicle on fire complicates the fire process. Targeting at dynamic changes oftemperature field distribution and smoke spread caused by moving vehicle on fire, the presentstudy uses analogy simulation experiment and numerical simulation to investigate theinfluence of moving fire on energy distribution and smoke spread in tunnel, which providesguidance for research and application on tunnel fire prevention and rescue.Taking the structure of Mont Blanc tunnel in which fire accident ever occurred due tomoving vehicle on fire and typical domestic tunnels as prototype, the1:20reduced-scaleanalogy simulation tunnel model system is designed and established based on research objects.Through mass loss rate test of fuel, turbulence and stability influenced by moving fire onflame are analyzed. The function of the relation between flame shape, heat release rate of fireand velocity of moving fire is obtained.Based on analogy experimental system, analogy simulation experiments are carried outon moving fire traveling in tunnel at different velocities. From the curve change oftemperature, time-averaged temperature and maximum temperature of different detectors intunnel is studied, combining with fire zone thermal resisting, throttling effect and thermalpiston wind effect analysis, the law of influence of moving fire with different velocities onspacial temperature field distribution and energy change is possessed. The mutual functionrelationship between longitudinal ventilation and moving fire in tunnel is revealed as well.Through analogy simulation experiment, the influence of moving fire with differentvelocities on smoke spread speed in tunnel under natural ventilation is studied. Combinedwith analysis of fire zone thermal resisting and throttling effect and thermal piston wind effect of moving fire synthetically functions on tunnel space, the law was drawn on relation ofmoving fire with different velocities asymmetrically influences smoke spread in forward andbackward parts of fire source in tunnel.Based on basic principle of numerical heat transfer and analogy simulation experiment,numerical model of moving fire in tunnel is established; through fire dynamic numericalsimulation, air flow filed, pressure field, temperature isosurface and smoke concentrationdistribution in tunnel under moving fire condition are studied;the law on influence of movingfire on air field and pressure field distributon in tunnel is drawn, and the restrain effect oflongitudinal ventilation on backflow of heat flux is analyzed. On the basis of the research,the threat of the moving fire to people trapped in tunnel is clarified, and the principle andmeasures are provided for people to escape and vehicles to be guided in the early age whenmoving vehicle on fire advances into tunnel.