Experimental Study On Fire Behavior And Temperature Field In Long Distance And Heavy Haul Railway Tunnel

Long-distance and heavy-duty railways have become one of the most important means of modern transportation due to their high efficiency and low cost when carrying goods.Freight trains have a large amount of cargo and the cargoes are usually large-scale combustible raw materials.Such combustibles will quickly release a large amount of heat after being ignited.In the narrow and long confined space of long-distance and heavy-duty railway,the fire source will spread rapidly to form a large-scale tunnel fire,which will seriously damage the tunnel structure and bring huge economic losses.In this paper,a 1:10 scale-reduced experimental platform is used to carry out similar simulation research on the combustion characteristics of the continuous fire source of the tunnel ignition source under the open and closed state of the entrance and exit.The development law of tunnel fire is studied by changing the size of the oil pan when the entrance and exit are open and closed.When the entrance and exit are open,the development of tunnel fire can be divided into the initial stage,the development stage,the stable stage and the attenuation stage.In each stage,the flame shape,The change curve of mass loss rate,ceiling center temperature and longitudinal temperature under the ceiling all conform to the law of tunnel fire development.When the entrance and exit are closed,the tunnel fire development can be divided into a rapid development stage and a rapid decay stage.After the entrance and exit are closed,the flame inclination becomes larger,and the mass loss rate of fuel shows a rapid increase and rapid decrease.The ceiling center temperature rises after reaching the peak.Rapid decline,so the suffocation measures are taken before the tunnel fire develops to the stable stage,and the effect is better;the longitudinal temperature under the ceiling is symmetrically distributed on both sides of the fire source,and the longitudinal temperature attenuates faster at the ceiling position closer to the fire source.quick.By changing the distance between the fire source in the open and closed state of the entrance and exit,the fire combustion characteristics of the tunnel with dual fire sources are studied,and the coupling effect of radiant heat feedback and air entrainment is analyzed.When the S/D is 0.5,the radiant heat feedback is strong,and the air entrainment is limited,so that the flame vertical fusion degree is high,the flame height is the largest,and the longitudinal temperature under the ceiling is the lowest;when the S/D is near 1,the radiant heat feedback Competing with air entrainment,the flame has a significant angle of inclination but the flame is not fused,and the longitudinal temperature under the average ceiling in the tunnel is the highest;when the S/D is 2,the fire source spacing is larger,and the heat radiation feedback is weakened,making the flames vertical upward.Influence,the longitudinal temperature under the ceiling is low.After the inlet and outlet are closed,the flame changes from a steady state to a slender state,and extinguishes after severe shaking.The ceiling center temperature rises to an unsteady peak in a short period of time and then begins to decrease continuously,and the ceiling center temperature decreases from fast to slow During this process,the ceiling position directly above the two fire sources replaced the original ceiling center position and became the highest temperature point under the tunnel ceiling.The longitudinal temperature attenuation under the ceiling near the fire site was huge,while the longitudinal temperature under the ceiling at the far fire site was basically unchanged.Affected.The interaction between tunnel fire sources was studied by changing the size of the oil pan with the inlet and outlet open and closed.When the inlet and outlet are open,the flame inclination of oil pan 1 gradually increases as the fire source burns.When oil pan 1 remains unchanged and oil pan 2 becomes larger,oil pan 2 will promote the combustion of oil pan 1,but the promotion effect is achieved.After the upper limit is no longer enhanced,the specific manifestation is:the peak time of the ceiling temperature at different ceiling positions is advanced,and the advance time is similar,the longitudinal temperature of the near fire field decays sharply,but the longitudinal temperature of the far fire field is not affected;the oil pan 2 remains unchanged,When the oil pan 1 becomes larger,the suppression effect of the oil pan 1 on the oil pan 2 will be enhanced.The specific performance is as follows:the time required for the ceiling temperature curve to reach the peak is shortened overall,and the time required for the ceiling temperature of the far fire field to reach the peak is shorter.The longitudinal temperature decays sharply,and the longitudinal temperature of the far fire field rises slightly.When the inlet and outlet are closed,the flame inclination decreases,the mass loss rate of the oil pan increases exponentially and reaches the peak,and then begins to decline rapidly.The ceiling center temperature will continue to rise and reach a quasi-stable peak,and then rapidly decrease.The impact is small,and the longitudinal temperature distribution of all working conditions obeys the exponential distribution.Figure[44]Table[7]Reference[82]...