Experimental Research On The Flashpoint-Boiling Point Of Flammable Liquid And Their Applications Under Low Pressure

Flying has gradually become a common way to travel, but the aircraft safety has caught increasing attention.According to relevant data, the fuel tank explosion caused crashes have accounted for nearly 15 percent ofthe aircraft accidents. Furthermore, the uneven distribution of flammable liquid fuels and rapidly growing demand have led to an expansion of oil-pipeline transportation, but some of the transportation pipelines need to cross over the special environment of high-altitude hypobaric hypoxia, such as the petroleum products transportation pipeline from Golmud to Lhasa, and the refined oil transportation pipelines for southwest etc.. Therefore, the fire safety precautions of flammable liquids have been more prominent at the special environment of high-altitude hypobaric hypoxia. In order to provide a scientific basis and theoretical support for the aircraft flight safety design, the oil transportation pipeline and its fire safety control on the high altitudes, it is necessary to research on the fire hazards and control technologies of flammable liquid under special environments.Flashpoint, the minimum temperature for the flames spreading to the flammable liquid surface when the flames are tested to combustion the flammable liquid vapors under the specified conditions is usually used as an indicator to estimate the risk of flammable liquid fires. Therefore, This study conducted the experimental research on the flashpoint-boiling point of flammable liquid and their applications under low pressure to reveal the variations of the fire hazards of flammable liquid at the special environment of high-altitude hypobaric hypoxia. And based on this, the author also carried out the correction research of the correction standard of flashpoint measurement and the criteria of the fire hazard classification of flammable liquid at different pressures.Firstly, through a self-designed portable flashpoint measuring device, the experimental field measurements were conducted to research flashpoint of flammable liquid at high-altitude hypobaric hypoxia with the six high altitude pilot of 3650 m, 3950 m,4250 m,4500 m,4750 m,5000 m chosen in the route of Lhasa (Alt.:3650 m, P:64 kPa)-Damxung (Alt.:4250 m, P:60 kPa)-Ka ken la (Alt.:5190 m, P:54 kPa) and low altitude pilot of HeFei (Alt.:58 m, P:101 kPa). By Clausius-Clapeyron Equation and the corresponding assumptions, the linear relationship between the reciprocal of flashpoint and the logarithm of ambient pressure was given. Combined with the relationship between the altitude and the ambient pressure, the linear relationship of reciprocal of flashpoint and the altitude is presented. In order to obtain more experimental data under wider pressure conditions and verify the accuracy of field experiments at high altitude, a low-pressure chamber was used to conduct the experimental measurements. The experimental results show that the theoretical relationship between ambient pressure and altitude with flashpoint of flammable liquid are 1/TF(P)∝lnP and 1/TF(H)∝H, and the result shows a good consistency with that of the field measurements. Also the relationship between the open-cup and closed-cup flashpoint under different ambient pressure (altitude) is analyzed.And to further reveal the influence of different ambient pressure (altitude) on fire hazard of flammable liquids and to find the physical parameters associated with the flashpoint of flammable liquids, we conducted experiments to measure the boiling point of flammable liquid at low pressures ranging from 35 kPa to 101 kPa using a low-pressure chamber. Based on previous research model, Combining the Clausius-Clapeyron Equation and the experimental data, the relationship between ambient pressure and altitude with boiling point of flammable liquid are 1/TB(P)∝lnP and 1/TB(H)∝H. Also based on the relationship between the flashpoint and the ambient pressure (the altitude), the relationship between the boiling point and flashpoint and ambient pressure (altitude) is presented as:1/TF(P&H)-1/TB(P&H)∝k.Based on the relationships between the ambient pressure (the altitude) and the flashpoint of flammable liquids, the correction research of the correction standard of flashpoint measurement and the criteria of the fire hazard classification of flammable liquid at different pressures were carried out.The results show that the nonlinear decrease of flashpoint of flammable liquid when the ambient pressure (the altitude is increased) is decreased. Therefore, the fire hazard of flammable liquid increased faster when the ambient pressure (the altitude is increased) is decreased. So we proposed amendments for the correction standard of flashpoint measurement and the criteria of the fire hazard classification of flammable liquid at the special environment of high-altitude hypobaric hypoxia.Finally, the field experiments of boilover was conducted under three different environments pressure (the altitude) in Hefei (Alt.:58 m, P:101 kPa)-Lhasa (Alt.: 3650 m, P:64 kPa)-Nagqu (Alt.:4500 m, P:57 kPa). Based on the variation of the boiling point of flammable liquids at different pressures and the impact of environments pressure on the law of the combustion of flammable liquids, the relationship between the occurrence time of the boilover phenomenon and ambient pressure (altitude) is presented as:1/t(P)∝P2. And it shows that the occurrence time of the boilover phenomenon delay when the ambient pressure (the altitude is increased) is decreased in the range of research pressure, and when the pressure decreases to a certain extent, the boilover phenomenon of the flammable liquids will disappear.