The influence of low atmospheric pressure on carbon monoxide of n-heptane pool fires

Experimental study on the burning behavior and combustion toxicity of corrugated cartons under varying sub-atmospheric pressure

An approved fire-protection method for in-flight freighter aircraft is aircraft depressurization. The objective of this study was to evaluate the influence of depressurization on the burning characteristics of typical combustibles based on large-scale corrugated cartons test data, which is believed to be valuable for aircraft fire safety engineering. The fuel mass loss, pressure, CO concentration, and axial temperature distribution were investigated in comparative tests conducted in a newly designed hypobaric chamber to simulate a depressurization process from 100 to 60 kPa with respective rates of decrease of 91, 182, and 328 Pa/s. The depressurization experimental results show that the fire plume temperature, burning rate and pressure have a good power function correlation. A theoretical analysis of the sub-atmospheric pressure dependence relationship on the burning rates was conducted to predict the burning behavior, showing good agreement with the experimental results. Two kinds of pressure effects on the burning control mechanism were proposed. For the convective heat feedback control, a 2/3 power law with pressure was formulated with experimental validation. For the radiation heat feedback influenced by soot emissivity and mean beam length, a 3/2 power law with pressure resulted.

Research on the influence of driving gas types in compound jet on extinguishing the pool fire

Compound jet fire extinguishing technology is an efficient technology for oil fires. The hydrophobic ultrafine dry powder is used for the solid phase in the compound jet, but it can't be supplied continuously due to the insufficient supply of compressed nitrogen. Thus, the feasibility of using the compressed air to replace the compressed nitrogen in the compound jet was explored. The key factor for the replacement, which influences the fire extinguishing efficiency, is the oxygen content in the contact point between the jet and the flame. Firstly, the oxygen content of the ultrafine powder jet driven by air or nitrogen were investigated by gas analyzer; Secondly, 150 L (liter) gas oil and 50 L water were put in a oil pan, the compared fire extinguishing experiments were conducted, the fire extinction time and the temperature drop range were investigated. In order to reveal the effect of ultrafine dry powder on oxygen content in gas jet, the experiment that spray the compressed nitrogen were conducted. The results show that there are not much differences for the two gases in extinguishing the pool fire, indicating that compressed air as the driving gas of the compound jet is feasible during fire extinguishing process.

Initial fuel temperature effects on burning rate of pool fire

The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs.