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 The influence of aliphatics on soot inception modelling

2021 ◽  
Author(s):  
Nemanja Ceranic
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Fluid Dynamic ◽  
Soot Volume Fraction ◽  
Surface Reactivity ◽  
Complex Nature ◽  
Laminar Diffusion Flames ◽  
Laminar Diffusion ◽  
Polycyclic Aromatic

Soot models have been investigated for several decades and many fundamental models exist that prescribe soot formation in agreement with experiments and theories. However, due to the complex nature of soot formation, not all pathways have been fully characterized. This work has numerically studied the influence that aliphatic based inception models have on soot formation for coflow laminar diffusion flames. CoFlame is the in-house parallelized FORTRAN code that was used to conduct this research. It solves the combustion fluid dynamic conservation equations for a variety of coflow laminar diffusion flames. New soot inception models have been developed for specific aliphatics in conjunction with polycyclic aromatic hydrocarbon based inception. The purpose of these models was not to be completely fundamental in nature, but more so a proof-of-concept in that an aliphatic based mechanism could account for soot formation deficiencies that exist with just PAH based inception. The aliphatic based inception models show potential to enhance predicative capability by increasing the prediction of the soot volume fraction along the centerline without degrading the prediction along the pathline of maximum soot. Additionally, the surface reactivity that was used to achieve these results lied closer in the range of numerically derived optimal values as compared to the surface reactivity that was needed to match peak soot concentrations without the aliphatic based inception models.

scholarly journals SOOT VOLUME FRACTION MEASUREMENTS IN A THREE-DIMENSIONAL LAMINAR DIFFUSION FLAME ESTABLISHED IN MICROGRAVITY

2006 ◽  
Vol 178 (5) ◽  
pp. 813-835 ◽  
Author(s):  
GUILLAUME LEGROS ◽  
PIERRE JOULAIN ◽  
JEAN-PIERRE VANTELON ◽  
ANDRES FUENTES ◽  
DENIS BERTHEAU ◽  
...  
Keyword(s):  
Diffusion Flame ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Soot Volume Fraction ◽  
Laminar Diffusion Flame ◽  
Laminar Diffusion

scholarly journals A Numerical Investigation on Soot Formation From Laminar Diffusion Flames of Ethylene/Methane Mixture

2008 ◽  
Author(s):  
Hongsheng Guo ◽  
Stephanie Trottier ◽  
Matthew R. Johnson ◽  
Gregory J. Smallwood
Keyword(s):  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Soot Volume Fraction ◽  
Fuel Mixture ◽  
Methyl Radical ◽  
Laminar Diffusion Flames ◽  
Laminar Diffusion ◽  
Methane Mixture ◽  
Phase Chemistry

The sooting propensity of laminar diffusion flames employing ethylene/methane mixture fuel is investigated by numerical simulation. Detailed gas phase chemistry and moments method are used to describe the chemical reaction process and soot particle dynamics, respectively. The numerical model captures the primary features experimentally observed previously. At constant temperatures of air and fuel mixture, both maximum soot volume fraction and soot yield monotonically decrease with increasing the fraction of carbon from methane in the fuel mixture. However, when the temperatures of air and fuel mixture are preheated so that the adiabatic temperatures of all flames are same, the variation of the maximum soot yield becomes higher than what would be expected from a linear combination of the flames of pure ethylene and pure methane, showing a synergistic phenomenon in soot formation. Further analysis of the details of the numerical results suggests that the synergistic phenomenon is caused by the combined effects of the variations in the concentrations of acetylene (C2H2) and methyl radical (CH3). When the fraction of carbon from methane in fuel mixture increases, the concentration of C2H2 monotonically decreases, whereas that of methyl radical increases, resulting in a synergistic phenomenon in the variation of propargyl (C3H3) radical concentration due to the reactions C2H2 + CH3 = PC3H4 + H and PC3H4 + H = C3H3 + H2. This synergistic phenomenon causes a qualitatively similar variation trend in the concentration of pyrene (A4) owing to the reaction paths C3H3 → A1 (benzene) → A2 (naphthalene) → A3 (phenanthrene) → A4. Consequently, the synergistic effect occurs for soot inception and PAH condensation rates, leading to the synergistic phenomenon in soot yield. The similar synergistic phenomenon is not observed in the variation of peak soot volume fraction, since the maximum surface growth rate monotonically decreases, as the fraction of carbon from methane in fuel mixture increases.

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.

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 Influence of H2O on Oxygen Enriched Diffusion Combustion of Natural Gas

2021 ◽  
Vol 39 (3) ◽  
pp. 925-932
Author(s):  
Xiang He ◽  
Xin Ren ◽  
Fanjin Zeng ◽  
Yindi Zhang ◽  
Yue Xin ◽  
...  
Keyword(s):  
Natural Gas ◽  
Carbon Black ◽  
Volume Fraction ◽  
Combustion Process ◽  
Clean Energy ◽  
Operating Conditions ◽  
Chemical Effect ◽  
Chemical Action ◽  
Chemical Effects ◽  
Combustion Technology

O2/H2O combustion technology, as the next generation of oxy-fuel combustion technology with great potential, can greatly increase the utilization rate of clean energy CH4. In this paper, the natural gas combustion process under 6 operating conditions of O2/H2O atmosphere and O2/FH2O atmosphere is numerically simulated. The horizontal analysis is carried out on the characteristics of H2O fraction, CO2 volume fraction and the amount of pollutants (NOx, carbon black), and in-depth exploration of the content of additive H2O and the influence of chemical action on the above characteristics. The research results show that the chemical effects of H2O have a negative effect on combustion temperature, and the physical effects are dominant. The chemical effects of H2O have a great impact on CO production and little effect on the production of CO when the proportion of H2O is 65-79%. The chemical effects of H2O inhibit the formation of NOx and carbon black when the proportion of H2O is within the range of 55-70%. The chemical effect has the greatest impact on the formation of dyes (NOx, carbon black) when the proportion of H2O is within the range of 65-70%.

Transient Development of Flame and Soot Distribution in Laminar Diffusion Flame With Preheated Air

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Bijan Kumar Mandal ◽  
Amitava Sarkar ◽  
Amitava Datta
Keyword(s):  
Diffusion Flame ◽  
Volume Fraction ◽  
Soot Formation ◽  
Initial Period ◽  
Qualitative Difference ◽  
Soot Volume Fraction ◽  
Soot Oxidation ◽  
Average Diameter ◽  
Conservation Equations ◽  
Soot Particles

A numerical investigation of the transient development of flame and soot distributions in a laminar axisymmetric coflowing diffusion flame of methane in air has been carried out considering the air preheating effect. The gas phase conservation equations of mass, momentum, energy, and species concentrations along with the conservation equations of soot mass concentration and number density are solved simultaneously, with appropriate boundary conditions, by an explicit finite difference method. Average soot diameters are then calculated from these results. It is observed that the soot is formed in the flame when the temperature exceeds 1300 K. The contribution of surface growth toward soot formation is more significant compared with that of nucleation. Once the soot particles reach the high temperature oxygen-enriched zone beyond the flame, the soot oxidation becomes important. During the initial period, when soot oxidation is not contributing significantly, some of the soot particles escape into the atmosphere. However, under steady condition the exhaust product gas is nonsooty. Preheating of air increases the soot volume fraction significantly. This is both due to more number of soot particles and the increase in the average diameter. However, preheating of air does not cause a qualitative difference in the development of the soot-laden zone during the flame transient period.

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.

Refinement of the two-color pyrometry method for application in a direct injection diesel and natural gas compression-ignition engine

2019 ◽  
Vol 233 (14) ◽  
pp. 3787-3800 ◽  
Author(s):  
Mahdiar Khosravi ◽  
Patrick Kirchen
Keyword(s):  
Low Temperature ◽  
Natural Gas ◽  
Internal Combustion Engines ◽  
Volume Fraction ◽  
Soot Formation ◽  
Soot Volume Fraction ◽  
System Response ◽  
Compression Ignition Engine ◽  
Soot Emissions ◽  
Non Linear System

The soot emissions from internal combustion engines have significant health and environmental impacts and, as such, are subject to increasingly stringent regulations. Two-color pyrometry provides the in-cylinder soot cloud temperature and soot volume fraction and can provide insight to the in-cylinder soot formation and oxidation processes to guide research for reducing engine-out soot emissions. This work demonstrates improvements to the two-color pyrometry methodology, with a focus on low-temperature, low-soot regimes such as low-temperature combustion or combustion of direct injected natural gas. Through selection of a fast and robust numerical algorithm, characterizing and increasing the detection envelope, performing static and dynamic perspective adjustments, accounting for non-uniform and non-linear system response, as well as localized signal-to-noise ratio enhancement through image filtering, the performance of the pyrometric method was improved by a 40% increase in the resolved signal fraction. The refined two-color method was evaluated for both direct injected diesel and natural gas fueling strategies using a pilot-ignited direct injected natural gas fuel system and facilitated evaluation of local temperatures and soot concentrations in pilot-ignited direct injected natural gas combustion, despite the generally low soot levels in this combustion strategy.

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