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Research Papers: Fuel Combustion

Effects of Diluents on Lifted Turbulent Methane and Ethylene Jet Flames

[+] Author and Article Information
Andrew R. Hutchins

Department of Mechanical
and Aerospace Engineering,
North Carolina State University,
911 Oval Drive, Box 7910,
NCSU Campus, Raleigh, NC 27695
e-mail: arhutch2@ncsu.edu

James D. Kribs, Kevin M. Lyons

Department of Mechanical
and Aerospace Engineering,
North Carolina State University,
911 Oval Drive,
Box 7910, NCSU Campus,
Raleigh, NC 27695

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received May 4, 2014; final manuscript received October 9, 2014; published online November 7, 2014. Assoc. Editor: Reza H. Sheikhi.

J. Energy Resour. Technol 137(3), 032204 (May 01, 2015) (6 pages) Paper No: JERT-14-1143; doi: 10.1115/1.4028865 History: Received May 04, 2014; Revised October 09, 2014; Online November 07, 2014

The effects of diluents on the liftoff of turbulent, partially premixed methane and ethylene jet flames for potential impact in industrial burner operation for multifuel operation have been investigated. Both fuel jets were diluted with nitrogen and argon in separate experiments, and the flame liftoff heights were compared for a variety of flow conditions. Methane flames have been shown to liftoff at lower jet velocities and reach blowout conditions much more rapidly than ethylene flames. Diluting ethylene and methane jets with nitrogen and argon, independently, resulted in varying trends for each fuel. At low dilution levels (∼5% by mole fraction), methane flames were lifted to similar heights, regardless of the diluent type; however, at higher dilution levels (∼10% by mole fraction) the argon diluent produced a flame which stabilized farther downstream. Ethylene jet flames proved to vary less in liftoff heights with respect to diluent type. Significant soot reduction with dilution is witnessed for both ethylene and methane flames, in that flame luminosity alteration occurs at the flame base at increasing levels of argon and nitrogen dilution. The increasing dilution levels also decreased the liftoff velocity of the fuel. Analysis showed little variance among liftoff heights in ethylene flames for the various inert diluents, while methane flames proved to be more sensitive to diluent type. This sensitivity is attributed to the more narrow limits of flammability of methane in comparison to ethylene, as well as the much higher flame speed of ethylene flames.

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References

Figures

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Fig. 1

Flame stability plot demonstrating various phases in flame propagation

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Fig. 2

Apparatus schematic utilized for fuel (methane/ethylene) and nonreactive diluents (nitrogen/argon) mixing and combustion

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Fig. 3

(a) Pure ethylene flame luminosity in comparison to high level (20% by mole fraction) dilution of nitrogen and (b) pure ethylene flame luminosity in comparison to high level (20% by mole fraction) dilution of argon

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Fig. 4

(a) Pure methane flame luminosity in comparison to low level (5% by mole fraction) dilution of nitrogen and (b) pure methane flame luminosity in comparison to low level (5% by mole fraction) dilution of argon

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Fig. 5

Trends of increasing methane jet flame liftoff height from the fuel nozzle with increasing fuel velocity and increasing inert gas dilution levels

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Fig. 6

Trends of increasing ethylene jet flame liftoff height from the fuel nozzle with increasing fuel velocity and increasing inert gas dilution levels

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Fig. 7

Trend of nondimensional methane jet flame liftoff versus methane mass flowrate with comparison of experimental to theoretical nondimensional liftoff height using the flame liftoff scaling formulation. The scaled points are those associated with the theoretical data, while the other points are experimental data points.

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Fig. 8

Trend of nondimensional ethylene jet flame liftoff versus ethylene mass flowrate with comparison of experimental to theoretical nondimensional liftoff height using the flame liftoff scaling formulation. The scaled points are those associated with the theoretical data, while the other points are experimental data points.

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Fig. 9

Comparison of experimental nondimensional liftoff heights to corrected theoretical nondimensional liftoff heights using the nondimensional modification to the flame liftoff scaling for methane jet flames. The corrected points are those associated with the theoretical data, while the other points are experimental data points.

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Fig. 10

Comparison of experimental nondimensional liftoff heights to corrected theoretical nondimensional liftoff heights using the nondimensional modification to the flame liftoff scaling for ethylene jet flames. The corrected points are those associated with the theoretical data, while the other points are experimental data points.

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