N-Heptane Pool Fire Behavior in a Controlled Oxygen and Low-Pressure Environment

2014 ◽  
Author(s):  
Quanyi Liu ◽  
Kewei Chen ◽  
Nan Wu ◽  
Jiusheng Yin ◽  
Rui Yang ◽  
...  
Keyword(s):  
High Altitude ◽  
Radiative Heat ◽  
Flame Temperature ◽  
Fire Behavior ◽  
Low Pressure ◽  
Pool Fire ◽  
Fire Tests ◽  
Mass Burning Rate ◽  
Low Oxygen ◽  
Lower Temperature

Fires at high altitude airports have attracted a lot of attention. Such fires show some special characteristics because of the coupling impact of low pressure and low oxygen levels. Some experiments, which were conducted recently at high altitude locations, such as Lhasa and in some low pressure chambers, were usually extinguished due to the limited supply of oxygen. In order to reveal the dependence of fire behavior on pressure comprehensively, a low-pressure chamber with ventilation control of 2×3×4.65m3 in volume has been developed and built, which can allow larger scale fire tests to be conducted and simulate more realistic high-altitude environment. In this study, pool fire tests using 20-cm and 30-cm-diameter pans are configured under five different static pressures, e.g. 101kPa, 75kPa, 64kPa, 38kPa and 24kPa. Each test has been repeated three times. The parameters measured include flame temperature, radiative heat flux, and mass loss etc. It is concluded that under lower pressure, mass burning rate is lower, temperature is higher, and height of the flame is higher, which demonstrated that low pressure fire is more dangerous to the buildings at high altitude airports.

Modeling on n-Heptane Pool Fire Behavior in an Altitude Chamber

2013 ◽  
Author(s):  
Quanyi Liu ◽  
Wei Yao ◽  
Jiusheng Yin ◽  
Rui Yang ◽  
Hui Zhang
Keyword(s):  
High Altitude ◽  
Burning Rate ◽  
Pressure Effect ◽  
Fire Behavior ◽  
Low Pressure ◽  
Pool Fire ◽  
Low Oxygen ◽  
Fire Plume ◽  
Plume Temperature ◽  
Modeling Data

Airplane as one of the important transport vehicles in our life, its safety problem related to in-flight fire has attracted a wide-spread attention. The combustion behavior of the cabin fire in flight shows some special characteristics because of the high-altitude environment with low-pressure and low oxygen concentration. A low-pressure chamber of size 2 m×3 m×2 m has been built to simulate high-altitude environments, where multiple static pressures for pool fire tests can be configured in the range between standard atmospheric pressure 101.3KPa and 30KPa. Two different sizes of pool fires were tested. Then corresponding modeling were conducted by a LES code FDS V5.5 to examine the mechanism of pressure effect on the n-Heptane pool fire behavior. The burning of liquid fuel was modeled by a Clausius-Clapeyron relation based liquid pyrolysis model. The modeling data was validated against the experimental measurements. The mass burning rate of free-burning pool fire decreases with the decreasing of pressure, which was observed from the modeling to be due to the reduction of flame heat feedback to the fuel surface. Under low pressure, the fire plume temperature increases for the same burning rate. The mechanism of pressure effect on fire behavior was analyzed based on the modeling data.

scholarly journals Experimental study on burning behaviors of liquid fuels with different sooting levels at high altitude

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2533-2541 ◽  
Author(s):  
Jiahao Liu ◽  
Pan Li ◽  
Mingyi Chen ◽  
Xiao Chen ◽  
Richard Yuen ◽  
...  
Keyword(s):  
High Altitude ◽  
Scaling Laws ◽  
Radiative Heat ◽  
Volume Fraction ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Low Pressure ◽  
Heat Fluxes ◽  
Liquid Fuels ◽  
Axial Temperature

To validate the feasibility of classical fire scaling laws under low pressure, three typical liquid fuels with different sooting levels, i. e. ethanol, n-heptane and jet-A, were employed in this paper to perform a sequence of pool fires in a high altitude city, Lhasa, Tibet, China (3650 m, 64.3 kPa). Mass loss, axial temperature profile and radiative heat flux were recorded in each test. From the assessment of experimental data, it can be concluded that the dimensionless burning intensity m?? /D can be correlated against the Grashof number to different powers for all the three fuels, and the exponent increases with the sooting level of fuels. A correlated relationship expressed as ?T ~ [z(P/Q)2/5 ]? can be applied to analyze the axial temperature rises, partitioning flame region, intermittent region and plume region with the modified demarcations, i. e. 0.42 and 1.06. In addition, the averaged flame temperature grows higher with declining sooting level of fuels, while the radiative heat fluxes exhibit the opposite results. Moreover, the measured radiative heat fluxes for different fuels are proportional to 5 m f L T , and the soot volume fraction apparently increases with the sooting level of the fuels under low pressure condition.

Experiment Study of Cardboard Box Fire Behavior Under Dynamic Pressure in an Altitude Chamber

2015 ◽  
Author(s):  
Runhe Tian ◽  
Quanyi Liu ◽  
Rui Feng ◽  
Kewei Chen ◽  
Rui Yang ◽  
...  
Keyword(s):  
Radiative Heat ◽  
Dynamic Pressure ◽  
Ambient Pressure ◽  
Flame Temperature ◽  
Fire Behavior ◽  
Measurement Data ◽  
Safety Engineering ◽  
Mass Burning Rate ◽  
Experiment Study ◽  
Controlling System

Fires recently at low ambient pressure such as cruising airplane and high altitude airport have attracted great attention. Understanding fire behavior under low pressure is one of important fundamental problems for fire safety engineering design in forementioned environment. Observation of cardboard fires under dynamic pressure is of significant meaning to study continuous variation of fire behaviors of solid fuel during depressurization. An altitude chamber of 2×3×4.65 m3 with a powerful pressure controlling system was designed to observe fire behavior of cardboard fires under dynamic pressure. In the chamber, two configurations of cardboard boxes filled with shredded office paper were tested under dynamic pressures at descent rates: 5.46kPa/min, 10.92kPa/min, and 19.68kPa/min for both configurations. Measured parameters in this study include flame temperature, radiative heat flux, and mass burning rate. The measurement data were analyzed to reveal depressurization effect on fire behavior.

Solid Fuel Fire Behavior Under Fixed Pressure in a Low-Pressure Chamber

2015 ◽  
Author(s):  
Rui Feng ◽  
Quanyi Liu ◽  
Runhe Tian ◽  
Kewei Chen ◽  
Rui Yang ◽  
...  
Keyword(s):  
Burning Rate ◽  
Solid Fuel ◽  
Fire Behavior ◽  
Low Pressure ◽  
Pressure Chamber ◽  
Fire Tests ◽  
Mass Burning Rate ◽  
Base Dimension ◽  
The Difference ◽  
Fire Characteristics

To comprehensively reveal the difference of solid fuel fire characteristics at different altitudes, fire experiments of cardboard boxes at multiple static pressures with two configurations filled with shredded office paper were conducted in a low-pressure chamber. The measured parameters are mass burning rate, radiative heat flux, oxygen concentration and heat release rate (HRR) etc. The mass burning rate divided by fire base dimension ṁ/D is correlated against the production of pressure-squared times length-cubed (P2L3) to the power of 0.29 based on current cardboard boxes fire test data. HRR of two boxes fire tests are higher than that of one box fire tests under fixed pressures. However, there are a higher peak of HRR under a fixed higher pressure for one-box fire tests while a lower peak of HRR under a higher pressure for two-box fire tests. The HRR would decrease sharply after reaching the peak.

Experimental study of large-scale fire behavior under low pressure at high altitude

2013 ◽  
Vol 31 (6) ◽  
pp. 481-494 ◽  
Author(s):  
Wei Yao ◽  
Xiaokang Hu ◽  
Jianzhong Rong ◽  
Jian Wang ◽  
Hui Zhang
Keyword(s):  
Experimental Study ◽  
High Altitude ◽  
Large Scale ◽  
Fire Behavior ◽  
Low Pressure

The Mass Burning Rate of n-Heptane Pool Fire Under Dynamic Pressure

2016 ◽  
Author(s):  
Qiuju Ma ◽  
Quanyi Liu ◽  
Runhe Tian ◽  
Junjian Ye ◽  
Rui Yang ◽  
...  
Keyword(s):  
Burning Rate ◽  
Cold Water ◽  
Dynamic Pressure ◽  
Pressure Rise ◽  
Low Pressure ◽  
Pool Fire ◽  
Chamber Pressure ◽  
Pure Liquid ◽  
Mass Burning Rate ◽  
The Impact

Fire safety is critical for safety of airplane operation. During an emergency landing, airplane goes through dramatic external pressure change from cruise altitude to sea level, considering the impact caused by low pressure atmosphere. The objective of this work is to examine the effect of dynamic pressure on the behavior of a horizontally burning diffusion flame over a pool fuel surface based on experimental approach. The experiments were conducted in a large-scale altitude chamber of size 2 m × 3 m × 4.65 m. The pressure rise process was examined under different dynamic pressures from respectively 38 kPa, 64 kPa and 75 kPa to 90 kPa with various pressure rise rates of 100 Pa/s, 150 Pa/s, 200 Pa/s, 250 Pa/s and 300 Pa/s, which is to simulate the airplane landing process from different altitudes. The whole system of the altitude chamber is of unique capability that the pressure in the chamber can be exactly controlled by a powerful pressure controlling system, and the oxygen concentration can maintain at the level about 20%, which are achieved through controlling inlet air flow for oxygen level and outlet gas flow for pressure (static or dynamic) level. A round steel fuel pans of 34 cm in diameter and 15 cm in height were chosen for the pool fire tests. The fuel pan was filled with 99% pure liquid n-Heptane. Cold water is added beneath the fuel layer to cool the pan and minimize the temperature rise in the fuel. Parameters such as mass, mass burning rate, chamber pressure were measured. The results of those tests demonstrated the significant impact to fire behaviors caused by high altitude or low pressure atmosphere.

Controlling Effect of Oxygen Concentration on Fire Behavior in Low Air Pressure Cargo Compartment

2017 ◽  
Author(s):  
Wei Wang ◽  
Hui Zhang ◽  
Rui Yang ◽  
Qiuju Ma ◽  
Xiaodong Liu ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Atmospheric Pressure ◽  
Flame Temperature ◽  
Fire Behavior ◽  
Air Pressure ◽  
Gas Composition ◽  
Compartment Fire ◽  
Mass Burning Rate ◽  
Air Intake ◽  
Low Atmospheric Pressure

Cargo compartment fire has become the major security threat for cruising aircraft, the depressurization measurement could effectively suppress the cargo compartment fire through the reduction of the air pressure and oxygen concentration. The objective of this work is to study fire behavior characteristics in half confined chamber and high altitude laboratory at identical low atmospheric pressure, and explore the controlling effects of air exhaust condition, oxygen concentration. N-heptane pool fire experiments were conducted separately in Langfang low pressure chamber (altitude 50m) and Kangding airport laboratory (altitude 4290m) at 60 kPa air pressure, both assembled ISO-9705, but their gas supplying condition is different. Mass burning rate, gas composition, flame temperature, and radiant heat flux had been measured as the principal characteristic parameters for analysis. This paper reveals the variation characteristics of the fire behavior under different oxygen concentration but identical low atmospheric pressure. The gas composition of the chamber is controlled by the liquid fire and air intake quantity, the oxygen concentration of the chamber decreases with decreasing gas intake quantity. The mass burning rate increases and the mass burning time decreases with the increase of the oxygen concentration. The higher air intake quantity or the higher oxygen concentration could increase cargo compartment fire radiation intensity, and exacerbate the fire further propagation. However, under the low oxygen concentration condition, the liquid fire still have a higher flame temperature above a certain height. The depressurization measurement could increase the flame height and flame temperature may be caused the cabin fire-resistant liners layer is easier to burn through. The more reasonable adjustment of the cargo compartment air exhaust quantity and air pressure is very meaningful for the comprehensive fire suppression of cruising commercial airplanes.

scholarly journals Oxygen regulation of macrophage migration inhibitory factor in human placenta

2007 ◽  
Vol 292 (1) ◽  
pp. E272-E280 ◽  
Author(s):  
Francesca Ietta ◽  
Yuanhong Wu ◽  
Roberta Romagnoli ◽  
Nima Soleymanlou ◽  
Barbara Orsini ◽  
...  
Keyword(s):  
High Altitude ◽  
Migration Inhibitory Factor ◽  
Macrophage Migration Inhibitory Factor ◽  
Inhibitory Factor ◽  
Extravillous Trophoblast ◽  
Macrophage Migration ◽  
Low Oxygen ◽  
Placental Development

Macrophage migration inhibitory factor (MIF) is an important proinflammatory cytokine involved in regulation of macrophage function. In addition, MIF may also play a role in murine and human reproduction. Although both first trimester trophoblast and decidua express MIF, the regulation and functional significance of this cytokine during human placental development remains unclear. We assessed MIF expression throughout normal human placental development, as well as in in vitro (chorionic villous explants) and in vivo (high altitude placentae) models of human placental hypoxia. Dimethyloxalylglycine (DMOG), which stabilizes hypoxia inducible factor-1 under normoxic conditions, was also used to mimic the effects of hypoxia on MIF expression. Quantitative real-time PCR and Western blot analysis showed high MIF protein and mRNA expression at 7–10 wk and lower levels at 11–12 wk until term. Exposure of villous explants to 3% O2 resulted in increased MIF expression and secretion relative to standard conditions (20% O2). DMOG treatment under 20% O2 increased MIF expression. In situ hybridization and immunohistochemistry showed elevated MIF expression in low oxygen-induced extravillous trophoblast cells. Finally, a significant increase in MIF transcript was observed in placental tissues from high-altitude pregnancies. Hence, three experimental models of placental hypoxia (early gestation, DMOG treatment, and high altitude) converge in stimulating increased MIF, supporting the conclusion that placental-derived MIF is an oxygen-responsive cytokine highly expressed in physiological in vivo and in in vitro low oxygen conditions.

Effect of O2 Partial Pressure on Post Annealed Ba2YCU3O7-δ Thin Films

1992 ◽  
Vol 275 ◽  
Author(s):  
Julia M. PhUlips ◽  
M. P. Siegal ◽  
S. Y. Hou ◽  
T. H. Tiefel ◽  
J. H. Marshall
Keyword(s):  
Partial Pressure ◽  
Film Growth ◽  
Epitaxial Films ◽  
Pinning Force ◽  
Low Oxygen ◽  
O2 Partial Pressure ◽  
Growth Method ◽  
Lower Temperature ◽  
The Relationship

ABSTRACTEpitaxial films of Ba2YCu3O7-δ (BYCO) as thin as 250 å A and with Jc's approaching those of the best in situ grown films can be formed by co-evaporating BaF2, Y, and Cu followed by a two-stage anneal. These results extend the work on films > 2000 Å thick by R. Feenstra et al. [J. Appl. Phys. 69, 6569 (1991)]. High quality films of these thicknesses become possible if low oxygen partial pressure [p(O2) = 4.3 Torr] is used during the high temperature portion cf the anneal (Ta). The BYCO melt line is the upper limit for Ta. The use of low p(O2) shifts the window for stable BYCO film growth to lower temperature, which allows the formation of smooth films with greater microstructural disorder than is found in films grown in p(O2) = 740 Torr at higher Ta. The best films annealed in p(O2)=4.3 Torr have Jc values a factor of four higher than do comparable films annealed in P2=740 Torr. The relationship between the T required to grow films with the strongest pinning force and p(O2) is log independent of growth method (in situ or situ) over a range of five orders of magnitude of P(O2).

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