Lift-Off Stability of n-Heptane Jet Diffusion Flames in Homogeneous Environments of Fuel and Air

1997 ◽  
Vol 119 (1) ◽  
pp. 45-48
Author(s):  
P. Samuel ◽  
G. A. Karim
Keyword(s):  
Liquid Fuel ◽  
Diffusion Flames ◽  
Jet Fuel ◽  
Small Concentration ◽  
Stream Velocity ◽  
Jet Flame ◽  
Jet Diffusion Flames ◽  
Discharge Velocity ◽  
Lift Off ◽  
Made In

The lift-off of jet diffusion flames of a liquid fuel in coflowing streams of air was established experimentally for a range of jet discharge and stream velocities. The improvement in the lift-off stability of the flame due to the presence of a small concentration of an auxiliary gaseous fuel in the surrounding air was established. Liquid n-heptane was the jet fuel while methane, ethylene, propane, and hydrogen were employed individually in small concentrations as the auxiliary fuels. It is shown that the lift-off distance and the corresponding ignition delay of the jet flame can be correlated for all the observations made in terms of derived dimensionless grouping of the main parameters varied, which included the jet discharge velocity, the surrounding stream velocity, and the concentration of the fuel added to the surroundings of the flame.

Lift-Off, Reattachment and Blowout Limits of Co-Flow Jet Diffusion Flames

2002 ◽  
Author(s):  
M. Karbasi ◽  
I. Wierzba
Keyword(s):  
Diffusion Flames ◽  
Flame Stabilization ◽  
Nozzle Geometry ◽  
Stream Velocity ◽  
Jet Diffusion Flames ◽  
Air Stream ◽  
Lifted Flames ◽  
Lift Off ◽  
The Stability ◽  
Flowing Stream

The stability behaviour of jet diffusion flames in a co-flowing stream of air was examined. Their lift-off, reattachment and blowout limits were established for methane, propane, ethylene and hydrogen. The co-flowing air stream velocity affected significantly the mechanism of flame stabilization. Different flow regimes where the blowout of lifted flames or attached flames can occur were recognized. A transition region in which both the blowout of lifted flames as well as that of attached flames was observed and identified with respect to the value of the air stream velocity. It was found that the blowout limits for lifted flames in this region were much smaller than for the attached flames. The effects of changes in the nozzle geometry and co-flowing stream composition were also considered.

Prediction and Validation of Blowout Limits of Co-Flowing Jet Diffusion Flames—Effect of Dilution

1998 ◽  
Vol 120 (2) ◽  
pp. 167-171 ◽  
Author(s):  
M. Karbasi ◽  
I. Wierzba
Keyword(s):  
Carbon Dioxide ◽  
Time Scale ◽  
Diffusion Flames ◽  
Mixing Time ◽  
Stability Limit ◽  
Jet Fuel ◽  
Stream Velocity ◽  
Jet Diffusion Flames ◽  
Air Stream ◽  
Scale Ratio

The blowout limits of a co-flowing turbulent methane jet diffusion flame with addition of diluent in either jet fuel or surrounding air stream is studied both analytically and experimentally. Helium, nitrogen, and carbon dioxide were employed as the diluents. Experiments indicated that an addition of diluents to the jet fuel or surrounding air stream decreased the stability limit of the jet diffusion flames. The strongest effect was observed with carbon dioxide as the diluent followed by nitrogen and then by helium. A model of extinction based on recognized criterion of the mixing time scale to characteristic combustion time scale ratio using experimentally derived correlations is proposed. It is capable of predicting the large reduction of the jet blowout velocity due to a relatively small increase in the co-flow stream velocity along with an increase in the concentration of diluent in either the jet fuel or surrounding air stream. Experiments were carried out to validate the model. The predicted blowout velocities of turbulent jet diffusion flames obtained using this model are in good agreement with the corresponding experimental data.

Effect of Diluent on the Blowout Limits of Jet Diffusion Flames

2001 ◽  
Author(s):  
N. Papanikolaou ◽  
I. Wierzba ◽  
V. W. Liu
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Flow Field ◽  
Diffusion Flames ◽  
Jet Fuel ◽  
Field Structure ◽  
Jet Diffusion Flames ◽  
Air Stream ◽  
Lifted Flames

Abstract The paper will describe the results of an experimental investigation on the effect of diluents premixed with either the jet or co-flowing air stream on the blowout limits and flow field structure of jet diffusion flames. Experiments were conducted for a range of co-flowing air stream velocities with methane as the primary jet fuel, and nitrogen and carbon dioxide as diluents in the jet fuel; carbon dioxide was also used in the co-flowing air stream. The addition of a diluent to the surrounding air stream had a much stronger effect on the blowout limits than the addition of the diluent to the jet fuel. The effect of partially premixing air with the jet fuel on the blowout limits was also investigated. The addition of air (to up to 30%) to the methane jet significantly reduced the blowout limits of lifted flames, but it had little effect on the blowout limits of attached flames, which was rather unexpected.

Subatmospheric Extinction of Opposed-Jet Diffusion Flames of Jet Fuel and Its Surrogates

AIAA Journal ◽  
2010 ◽  
Vol 48 (1) ◽  
pp. 158-165 ◽  
Author(s):  
Srinivasan Dattarajan ◽  
Okjoo Park ◽  
Elizabeth M. Fisher ◽  
Frederick C. Gouldin ◽  
Joseph W. Bozzelli
Keyword(s):  
Diffusion Flames ◽  
Jet Fuel ◽  
Jet Diffusion Flames ◽  
Opposed Jet

The Effects of Burner Geometry and Fuel Composition on the Stability of a Jet Diffusion Flame

1997 ◽  
Vol 119 (4) ◽  
pp. 265-270 ◽  
Author(s):  
N. Papanikolaou ◽  
I. Wierzba
Keyword(s):  
Diffusion Flames ◽  
Flame Stabilization ◽  
Nozzle Geometry ◽  
Stream Velocity ◽  
Fuel Composition ◽  
Jet Diffusion Flames ◽  
Aspect Ratios ◽  
Air Stream ◽  
The Stability ◽  
Flowing Stream

The effect of the burner configuration and fuel composition on the stability limits of jet diffusion flames issuing into a co-flowing air stream is presented. Circular and elliptic nozzles of various lip thicknesses and aspect ratios were employed with methane as the primary fuel and hydrogen, carbon dioxide, and nitrogen as additives. It was found that the effects of nozzle geometry, fuel composition, and co-flowing stream velocity on the blowout limits were highly dependent on the type of flame stabilization mechanism, i.e., whether lifted or rim-attached, just prior to blowout. The blowout behavior of lifted flames did not appear to be significantly affected by a change in the nozzle shape as long as the discharge area remained constant, but it was greatly affected by the fuel composition. In contrast, attached flame stability was influenced by both the fuel composition and the nozzle geometry which had the potential to extend the maximum co-flowing stream velocity without causing the flame to blow out. The parameters affecting the limiting stream velocity were studied.

Effect of Burner Geometry on the Blowout Limits of Jet Diffusion Flames in a Co-Flowing Oxidizing Stream

1996 ◽  
Vol 118 (2) ◽  
pp. 134-139 ◽  
Author(s):  
N. Papanikolaou ◽  
I. Wierzba
Keyword(s):  
Diffusion Flames ◽  
Flame Stabilization ◽  
Stream Velocity ◽  
Discharge Area ◽  
Jet Diffusion Flames ◽  
Air Stream ◽  
Lifted Flames ◽  
Nozzle Shape ◽  
The Stability ◽  
Flowing Stream

The effects of changes in the jet nozzle geometry, i.e., nozzle shape and lip thickness, on the blowout limits of jet diffusion flames in a co-flowing air stream were experimentally investigated for a range of co-flow air stream velocities. Circular and elongated nozzles of different axes rations were employed. Preliminary results showed that nozzles with low major-to-minor axes ratios improved, while high ratios reduced, the blowout limit of attached flames compared with that for an equivalent circular nozzle. The nozzle shape had no apparent influence on the blowout limits lifted flames and the limiting stream velocity. The experimental blowout limits of lifted flames were found to be a function of the co-flowing stream velocity and jet discharge area. On the other hand, the stability of attached flames was a function of the co-flowing stream velocity, jet discharge area as well as the nozzle shape. The effect of premixing a fuel with the surrounding air was also studied. Generally, the introduction of auxiliary fuel into the surrounding stream either increased or decreased the blowout limit depending on the type of flame stabilization mechanism prior to blowout. The stability mechanism of the flame was found to be a function of the co-flow stream velocity and the auxiliary fuel employed.

Numerical Simulation of Jet Diffusion Flames With Radiative Heat Transfer Modeling

2005 ◽  
Author(s):  
Mario Baburic´ ◽  
Reinhard Tatschl ◽  
Neven Duic´
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Radiative Heat Transfer ◽  
Diffusion Flame ◽  
Radiative Heat ◽  
Diffusion Flames ◽  
Flamelet Model ◽  
Jet Flame ◽  
Combustion Modeling ◽  
Jet Diffusion Flames

Beside appropriate turbulence and combustion modeling, the problem of an accurate prediction of turbulent diffusion flames usually requires accurate radiative heat transfer predictions as well. In this paper it is shown that the inclusion of radiation modeling into the overall numerical simulation is important if accurate temperature profiles are needed. Two different jet diffusion flame configurations are simulated in this work — a diluted hydrogen jet flame (80% H2 and 20% He by volume) [1–4], and a piloted methane jet diffusion flame (flame D) [5, 6]. The predictions are compared to experimental data. Radiation is modeled by a conservative discrete transfer radiation method (DTRM) [7, 8]. Turbulence is modeled by a classical k-ε and by a hybrid procedure, as proposed in [9]. Combustion modeling is based on the stationary laminar flamelet model (SLFM) [10], where the combustion/turbulence interaction is accomplished via the presumed β probability density function (β-PDF).

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