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.

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.

Impact of Soot Radiative Properties, Pressure and Soot Volume Fraction on Radiative Heat Transfer in Turbulent Sooty Flames

2020 ◽  
Author(s):  
Kevin Torres Monclard ◽  
Olivier Gicquel ◽  
Ronan Vicquelin
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Jet Flame ◽  
Soot Particles

Abstract The effect of soot radiation modeling, pressure, and level of soot volume fraction are investigated in two ethylene-air turbulent flames: a jet flame at atmospheric pressure studied at Sandia, and a confined pressurized flame studied at DLR. Both cases have previously been computed with large-eddy simulations coupled with thermal radiation. The present study aims at determining and analyzing the thermal radiation field for different models from these numerical results. A Monte-Carlo solver based on the Emission Reciprocity Method is used to solve the radiative transfer equation with detailed gas and soot properties in both configurations. The participating gases properties are described by an accurate narrowband ck model. Emission, absorption, and scattering from soot particles are accounted for. Two formulations of the soot refractive index are considered: a constant value and a wavelength formulation dependency. This is combined with different models for soot radiative properties: gray, Rayleigh theory, Rayleigh-Debye-Gans theory for fractal aggregates. The effects of soot radiative scattering is often neglected since their contribution is expected to be small. This contribution is determined quantitatively in different scenarios, showing great sensitivity to the soot particles morphology. For the same soot volume fraction, scattering from larger aggregates is found to modify the radiative heat transfer noticeably. Such a finding outlines the need for detailed information on soot particles. Finally, the role of soot volume fraction and pressure on radiative interactions between both solid and gaseous phases is investigated.

An experimental study on thermal radiation of fire whirl

2017 ◽  
Vol 26 (8) ◽  
pp. 693 ◽  
Author(s):  
Pengfei Wang ◽  
Naian Liu ◽  
Yueling Bai ◽  
Linhe Zhang ◽  
Kohyu Satoh ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Measured Data ◽  
Emissive Power ◽  
Air Curtain ◽  
Power Profile ◽  
Flame Emissivity ◽  
Fire Whirl ◽  
Infrared Methods

Fire whirl is frequently observed in wildland fires, and may cause serious difficulty in firefighting owing to its significant turbulent flow. In this paper, the radiation of fire whirl is investigated through experiments using a fire whirl facility made up of an air curtain apparatus, with five different sizes of n-heptane pools (25, 30, 35, 40 and 45 cm). The flame contour was extracted by image processing. By using infrared methods, the flame emissivity of fire whirl at different heights for different pool diameters was measured, and thereby a correlation was developed between the flame emissivity and the flame diameter. The soot volume fraction in the luminous flame is estimated to range within 2.5 × 10−6 to 4.0 × 10−6, much higher than that of general heptane pool fires, which provides an explanation of the higher flame emissivity of fire whirl. The emissive power profile v. normalised height is deduced from flame emissivity and flame temperature data. A multizone flame model (in which each zone is assumed as a grey body) is used, based on the measured data of flame emissivity, to predict the radiation of fire whirl. Comparison between the predicted and measured data of radiative flux shows good agreement.

Effect of Soot-Inhibitor Additives on the Thermal Structure and Soot Volume Fraction Inside Laminar Diffusion Natural Gas Flames

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
M. M. Ibrahim ◽  
A. Attia ◽  
H. A. Moneib ◽  
A. A. Emara
Keyword(s):  
Natural Gas ◽  
Volume Fraction ◽  
Thermal Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Soot Volume Fraction ◽  
Soot Oxidation ◽  
Growth Zone ◽  
Laminar Diffusion ◽  
The Individual

Abstract Soot study is a fundamental issue for the combustion process of hydrocarbon fuels. Losses in combustion efficiency, health risks, environmental loosestrife, and damage in furnaces may appear as a result of soot existence. This present paper aims at providing an experimental mapping of the changes in the soot volume fraction and axial flame mean temperature associated with the addition of different percentages of soot inhibitor additives (namely, Argon, Nitrogen, and Helium) in a vertical laminar diffusion natural gas flame issuing from a honeycomb circular burner. The soot volume fraction is acquired by the laser extinction technique, while the axial variations of the mean flame temperature are accomplished by a bare 51 µm (Pt-30%Rh versus Pt-6%Rh) thermocouple to render radiation loss insignificant. The concentration of the individual additives is varied from 5% to 25% (step 5%) and the experiments are conducted at a fixed natural gas throughput (350 mL/min) to ensure unvaried thermal input. Measurement traverses along and across (at fixed radial locations) are conducted. The fuel flowrate is measured by a precision digital gas flowmeter (type: Varian intelligent), while the flow of the individual additive is admitted via solenoid valves (handled with labview program) and is injected through mixing pipes located at burner entry. The different regimes of the soot inception (molecular; zone 1), soot growth zone (zone 2), and soot oxidation (zone 3) are accurately defined and assessed in relation to the temperature results for the different cases under investigation.

scholarly journals Fuel Molecular Structure and Flame Temperature Effects on Soot Formation in Gas Turbine Combustors

1990 ◽  
Vol 112 (1) ◽  
pp. 52-59 ◽  
Author(s):  
O¨. L. Gu¨lder ◽  
B. Glavincˇevski ◽  
M. F. Baksh
Keyword(s):  
Molecular Structure ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Empirical Relationship ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Temperature Fields ◽  
Diesel Fuels

A systematic study of soot formation along the centerlines of axisymmetric laminar diffusion flames of a large number of liquid hydrocarbons, hydrocarbon blends, and aviation turbine and diesel fuels was made. Measurements of the attenuation of a laser beam across the flame diameter were used to obtain the soot volume fraction, assuming Rayleigh extinction. Two sets of hydrocarbon blends were designed such that the molecular fuel composition varied considerably but the temperature fields in the flames were kept practically constant. Thus it was possible to separate the effects of molecular structure and the flame temperature on soot formation. It was quantitatively shown that the smoke point height is a lumped measure of fuel molecular constitution. The developed empirical relationship between soot volume fractions and fuel smoke point and hydrogen-to-carbon ratio was applied to five different combustor radiation data, and good agreement was obtained.

scholarly journals Growth of Soot Volume Fraction and Aggregate Size in 1D Premixed C2H4/Air Flames Studied by Laser-Induced Incandescence and Angle-Dependent Light Scattering

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
P. N. Langenkamp ◽  
J. A. van Oijen ◽  
H. B. Levinsky ◽  
A. V. Mokhov
Keyword(s):  
Light Scattering ◽  
Volume Fraction ◽  
Soot Formation ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Aggregate Size ◽  
Radius Of Gyration ◽  
Nonmonotonic Dependence ◽  
Volume Fractions ◽  
Laser Induced Incandescence

The growth of soot volume fraction and aggregate size was studied in burner-stabilized premixed C2H4/air flames with equivalence ratios between 2.0 and 2.35 as function of height above the burner using laser-induced incandescence (LII) to measure soot volume fractions and angle-dependent light scattering (ADLS) to measure corresponding aggregate sizes. Flame temperatures were varied at fixed equivalence ratio by changing the exit velocity of the unburned gas mixture. Temperatures were measured using spontaneous Raman scattering in flames with equivalence ratios up to ϕ = 2.1, with results showing good correspondence (within 50 K) with temperatures calculated using the San Diego mechanism. Both the soot volume fraction and radius of gyration strongly increase in richer flames. Furthermore, both show a nonmonotonic dependence on flame temperature, with a maximum occurring at ~1675 K for the volume fraction and ~1700 K for the radius of gyration. The measurement results were compared with calculations using two different semiempirical two-equation models of soot formation. Numerical calculations using both mechanisms substantially overpredict the measured soot volume fractions, although the models do better in richer flames. The model accounting for particle coagulation overpredicts the measured radii of gyration substantially for all equivalence ratios, although the calculated values improve at ϕ = 2.35.

Combustion Characteristics of Spray Flames of Canola Methyl Ester/Diesel Blends in a Furnace

2013 ◽  
Author(s):  
Cory D. Morton ◽  
Victor H. Tran ◽  
Ramkumar N. Parthasarathy ◽  
Subramanyam R. Gollahalli
Keyword(s):  
Methyl Ester ◽  
Heat Release ◽  
Volume Fraction ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Combustion Characteristics ◽  
Spray Flame ◽  
Spray Flames ◽  
Refractory Bricks ◽  
Emission Index

The combustion characteristics of spray flames of canola methyl ester (CME) and blends with diesel fuel within a re-radiating environment were studied. The combustion chamber was lined with refractory bricks that were preheated to about 725 K (1305 °R). The flow rates of the fuels provided a constant heat release rate of about 7.33 kW (25,000 BTU/hr) at atmospheric pressure. Measurements of flame temperature, in-flame concentrations, global emissions, flame radiation and soot volume fraction were taken. The global CO emission index was significantly lower in the biofuel blend spray flames compared to that of the diesel spray flame. The global NO emission index was comparable for all spray flames, which agreed with peak flame temperature and in-flame NO concentration measurements. The radiative fraction of heat release was also comparable for all spray flames.

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