Experimental investigation on soot volume fraction in an ethylene diffusion flame by emission spectrometry without optically-thin assumption

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.

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Computational Study of Fuel Dilution Effect on the Soot Formation in Methane-Air Laminar Confined Diffusion Flame

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-62901 ◽

2013 ◽

Author(s):

Achin Kumar Chowdhuri ◽

Arindam Mitra ◽

Somnath Chakraborti ◽

Bijan Kumar Mandal

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Diffusion Flame ◽

Volume Fraction ◽

Soot Formation ◽

Soot Volume Fraction ◽

Flame Height ◽

Fuel Jet ◽

Fuel Stream

Although diffusion flame is free from many problems associated with premixed flame, soot formation is a major problem in diffusion flame. The techniques of dilution of fuel or air with inert gases such as nitrogen and argon are used to decrease soot level in the flame. In this work, a CFD code has been developed to predict the flame height, soot volume fraction and soot number density in an axisymmetric laminar confined methane-air diffusion flame after diluting the fuel with nitrogen. The temperatures of the air and fuel at inlet are taken as 300K. Mass flow rate of the fuel stream is considered as 3.71×10−6 kg/s and mass flow rate of the air is taken as 2.2104×10−6 kg/s. The total mass flow rate through the central jet (fuel jet) is, however, kept constant. The radiation effect is also included through an optically thin radiation model. An explicit finite difference technique has been adopted for the numerical solution of reacting flow and two equations soot model with variable thermodynamic and transport properties. The prediction shows that flame height decreases with the addition of nitrogen to the fuel. Temperature of the flame is considerably reduced in the given computational domain. Both soot volume fraction and soot number density decrease with dilution by adding nitrogen in the fuel jet. The soot formation at different nitrogen dilution level of 0%, 10%, 20%, 30%, 40% and 50% are plotted and the soot get considerably reduced as the concentration of nitrogen is increased in the fuel stream.

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2D soot volume fraction imaging in an ethylene diffusion flame by two-color laser-induced incandescence (2C-LII) technique and comparison with results from other optical diagnostics

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2006.07.149 ◽

2007 ◽

Vol 31 (1) ◽

pp. 869-876 ◽

Cited By ~ 22

Author(s):

S. De Iuliis ◽

F. Migliorini ◽

F. Cignoli ◽

G. Zizak

Keyword(s):

Diffusion Flame ◽

Volume Fraction ◽

Soot Volume Fraction ◽

Optical Diagnostics ◽

Laser Induced Incandescence

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An Investigation of Soot Volume Fraction and Temperature for Natural Gas Laminar Diffusion Flame Established From a Honeycomb Gaseous Burner

Journal of Energy Resources Technology ◽

10.1115/1.4044123 ◽

2019 ◽

Vol 142 (1) ◽

Cited By ~ 1

Author(s):

M. M. Ibrahim ◽

A. Attia ◽

A. Emara ◽

H. A. Moneib

Keyword(s):

Diffusion Flame ◽

Volume Fraction ◽

Soot Formation ◽

Laser System ◽

Soot Volume Fraction ◽

Experimental Program ◽

Diffusion Combustion ◽

Gas Temperature ◽

Laminar Diffusion Flame ◽

Laminar Diffusion

The present work is an experimental investigation that aims at studying the effects of different fuel additives on the soot volume fraction and temperature in a well-defined vertical laminar diffusion flame configuration, and these additives include a diluent (argon) that suppresses the formation of soot and a soot promoter (acetylene) that accelerates and intensifies the soot formation. Three different measuring techniques are employed throughout the whole experimental program, namely, a high-resolution digital camera (up to 3.7 fps) for flame visualization, a bare wire Pt/Pt-13% rhodium fine thermocouple of 15 µm wire diameter for measuring the mean gas temperature inside the flame region and a laser system for measuring the in-flame soot volume fraction. The results indicated that the soot inception zone (deep dark parabolic shape) occurs at the immediate vicinity of the burner. The soot oxidation zone is characterized by high luminosity, and it begins after the fuel is largely consumed. The increased percentages of acetylene in the fuel mixture would lead to extending the length of this zone to ultimately occupy the whole visible flame length, where the luminosity becomes independent of the amount of soot. The temperature within the soot surface growth zone (orange color) continues increasing but at a lower rate that reflects the domination of diffusion combustion mode. Limited partial oxidation may be anticipated within this zone due to the relatively high temperature, which is not high enough to cause luminosity of the soot particles.

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Measurements of soot volume fraction in pulsed diffusion flame by laser induced incandescence

Experiments in Fluids ◽

10.1007/s00348-007-0382-3 ◽

2007 ◽

Vol 44 (1) ◽

pp. 137-144 ◽

Cited By ~ 2

Author(s):

Hayri Sapmaz ◽

Cheng-Xian Lin ◽

Chaouki Ghenai

Keyword(s):

Diffusion Flame ◽

Volume Fraction ◽

Soot Volume Fraction ◽

Laser Induced Incandescence

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A layer-peeling method for signal trapping correction in planar LII measurements of statistically steady flames

Measurement Science and Technology ◽

10.1088/1361-6501/ac370b ◽

2021 ◽

Author(s):

Felipe Escudero ◽

Juan José Cruz ◽

Fengshan Liu ◽

Andrés Fuentes

Keyword(s):

Diffusion Flame ◽

Volume Fraction ◽

Soot Volume Fraction ◽

Ccd Camera ◽

Computationally Efficient ◽

Trapping Effect ◽

Wide Range ◽

Planar Laser ◽

Soot Loading ◽

Layer Peeling

Abstract This work presents a layer-peeling (LP) algorithm to correct the signal trapping effect in planar laser-induced incandescence (LII) measurements of soot volume fraction. The method is based on measurements of LII signals captured by an intensified CCD camera at a series of parallel planes across a diffusion flame. A method based on presumed function (PF) of soot volume fraction is also proposed for comparison. The presented methods are numerically tested based on synthetic LII signals emitted from a simulated axisymmetric laminar diffusion flame using the CoFlame code. Numerical results showed that the LP method is able to correct the signal trapping effect, even for fairly large optical thicknesses and in a wide range of detection wavelengths. The correction decreases the relative errors induced by neglecting the trapping effect considerably. The signal trapping effect correction is less important for the determination of integrated soot quantities such as radially integrated soot volume fraction or total soot loading. Planar LII measurements were carried out and calibrated in order to test the method experimentally in a coflow flame. The LP, PF and a simplified analytical (SA) model were compared. The results indicate that the differences in soot volume fraction of 1 ppm or about 15% are obtained in zones of maximum soot loading of 6.5 ppm when the trapping effect is accounted for. Also, the LP and SA methods were found computationally efficient and accurate compared to the PF method. Although the study was performed in a canonical laminar axisymmetric flame, the proposed method can be applied to any statistically steady 3D flame.

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A Numerical Study of the Influence of Hydrogen Addition on Soot Formation in a Laminar Counterflow Ethylene/Oxygen/Nitrogen Diffusion Flame

Heat Transfer, Volume 2 ◽

10.1115/imece2004-59407 ◽

2004 ◽

Author(s):

Hongsheng Guo ◽

Fengshan Liu ◽

Gregory J. Smallwood

Keyword(s):

Diffusion Flame ◽

Volume Fraction ◽

Diffusion Flames ◽

Soot Formation ◽

Numerical Study ◽

Soot Volume Fraction ◽

Phase Reaction ◽

Nitrogen Diffusion ◽

Atom Concentration ◽

Hydrogen Addition

The influence of hydrogen addition to the fuel on soot formation in an ethylene/oxygen/nitrogen diffusion flame was numerically studied by simulation of three counterflow laminar diffusion flames at atmosphere pressure. The fuel mixtures for the three flames are pure ethylene, ethylene/hydrogen and ethylene/helium, respectively, while the oxidant is a mixture of oxygen and nitrogen. A detailed gas phase reaction mechanism including species up to benzene and complex thermal and transport properties were used. The soot inception and surface growth rates were, respectively, calculated based on benzene and HACA (H-abstraction and C2H2-addition) mechanisms. The predicted results for the three flames were compared and analyzed. It is indicated that although the addition of either hydrogen or helium to the fuel can reduce the soot volume fraction, the addition of hydrogen is more efficient. While the addition of helium reduces soot formation only through dilution, the addition of hydrogen suppresses soot formation through both dilution and chemical reaction effects. This conclusion is qualitatively consistent with available experiments. The simulations revel that the chemically inhibiting effect is caused by the decrease of hydrogen atom concentration in soot formation region, due to the displacement of the primary reaction zone, when hydrogen is added to the fuel.

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