Study On The Temperature Field Distribution And Flue Gas Flow Law Of Roof Under The Conditions Of Closed Pipe Gallery And Leakage Joint

The urban comprehensive pipe gallery is playing an increasingly important role in China's urban process.Because of the special narrow and long confined structure of the pipeline corridor and the underground conditions,when the pipeline fire occurs,a large number of heat and smoke generated by the fire can not be discharged in time,which easily causes the rapid spread of the fire,causing huge economic losses and adverse social impact.Therefore,it is of great significance to study the temperature distribution and smoke propagation characteristics of urban integrated pipe gallery fires.In this paper,three kinds of power sources are obtained by changing the size of square burner.It is found that the higher the power of the fire source,the higher the temperature in the corridor.Through the burning experiment of variable-power axisymmetric fire source for small-sized closed pipe gallery,the distribution of longitudinal temperature distribution and lateral wall temperature of the three power fire sources in the centerline of the pipe gallery is obtained.It is found that the longitudinal temperature rise decreases exponentially with the distance from the fire source,while the transverse temperature rise?35?T andQ^2/3H_ef^5/3are linear.The highest temperature occurs at the position directly above the dome fire source,and the temperature gradually decays from the middle to the sides.The fitting formulas of the maximum temperature rise of the longitudinal and transverse temperature fields of the roof jet formed by axisymmetric fire source in the closed pipe gallery are derived,and the influence of the power of the fire source on the temperature rise is excluded.In this paper,different degrees of restricted conditions are obtained by changing the distance of the fire source from the side wall of the pipe gallery.The combustion experiments of a single power non-axisymmetric fire source in a small enclosed corridor show that the flame shape and the transverse temperature distribution under the vault are different when the fire source is burned in different confined spaces.The closer the tube wall is to the fire source,the more obvious the flame leans to the left.When the fire source is placed close to the wall,the flame spreads upward along the arc pipe wall,forming an arc flame.Limited conditions also affect the transverse temperature distribution in the inner wall of the pipe gallery.With the shortening of the distance between the fire source and the tube wall,the maximum temperature point shifts from the center axis of the vault to the direction of the center axis deviating from the tube wall to 15 degrees.The temperature of the tube wall near the one end of the fire source and the gradient of temperature drop are higher than that on the other side of the tube wall.The flue gas sedimentation experiment was carried out on the pipe porch with a small size at one end,and the sedimentation law of the flue gas at the end of the leaked pipe gallery was obtained.Combined with the neutral layer theory,a prediction method based on the fire source power to predict the stable height of the smoke layer is proposed.It is found that the higher the power of the fire source,the faster the sedimentation rate of the smoke layer,and the lower the height of the smoke layer from the ground when it is stable.By studying the temperature near the fire source,it is found that the temperature near the fire plume appears as a"water jump zone",and the width increases with the increase of the fire source power.