| Spilling fire occurs from time to time in the process of storage and transportation of liquid fuels such as oil,compressed natural gas and chemical fuels.It has the characteristics of rapid development,easy to form large area fire,difficult to block and so on,which seriously endangers the safety of people’s lives and property.Spilling fire is a coupling behavior of flow and combustion,so the combination of fuel flow characteristics and combustion characteristics to reveal the spilling fire combustion mechanism can not only enrich the fire science theory,but also has a certain practical significance to promote the development of fire fighting.In previous studies,most of the spilling fire is ignited at the moment of leakage,but there are few studies on the steady flow state of spilled oil for a long time.In addition,most of the predecessors focused on the concurrent spilling fire that the direction of the spilled fuel and the spreading fire are same,and seldom carried out the opposed spilling fire research in which the direction of the spilled fuel is opposite to that of the spreading fire.In view of this,in this paper,two kinds of fuel trenches with length×width=100 cm×4.4 cm and 100 cm×20 cm were used to carry out the experiments of concurrent spilling fire and opposed spilling fire spread of n-butanol flow under the condition of steady flow with variable slopes and variable discharge flow rates.The variation law of flow characteristic parameters of n-butanol with variable slope and the characteristics of concurrent spilling fire are explained.The experiment of concurrent spilling fire was carried out by using a fuel trench with length×width=100 cm×4.4 cm.The results show that the bottom slope can accelerate the fuel diffusion velocity.In the range of 30 cm length,when the flow rate Q equals 392.1m L/min,the fuel diffusion rate increases by 31.5%when the slopeθ=1°and 76.1%whenθ=4°.For different slopes,the average flame height of n-butanol shows a"rising-decreasing-stable"trend with the leakage flow rate.When Q=160 m L/min,the flame height reaches the maximum,and after Q=370 m L/min,the flame height remains stable,and the flame spread mode is related to the relative size of fuel thickness and fuel diffusion rate.When the fuel rate and the slope of the trench increase to a certain extent,the spread speed of the concurrent spilling fire will gradually tend to be uniform,and the pulsation frequency will be close to zero.The critical flow criterion and heat transfer mechanism of opposed spilling fire of n-butanol with variable slope are revealed.The opposed spilling fire experiment was carried out by using the fuel trench with length×width=100 cm×20 cm,the force analysis of the subsurface flow area was carried out,the critical discharge flow rate was defined,and the spreading model of opposed spilling fire was established,which was used to calculate the critical discharge flow rate of theoretical opposed spilling fire.The relative error between the theoretical critical discharge flow rate and the experimental value was less than 20%.According to the heat transfer analysis of the subsurface flow area,the ratio ofQ（5）cd,l and)TQ(5 decreased from 52.7%to 29.7%,The ratio ofQ（5）cv and)TQ(5 increased from 46.3%to 69.7%when the discharge flow rate Q changes from 190 m L/min to 350 m L/min.Therefore,with the increase of discharge flow rate,forced convection heat transfer will gradually replace the convective heat transfer between the subsurface flow and the bottom of the fuel trench to become the main heat dissipation. |
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