Stability and Blowout Behavior of Jet Flames in Oblique Air Flows

Gomes, Jonathan N.; Kribs, James D.; Lyons, Kent

doi:10.1155/2012/218916

Cited by 3 publications

(1 citation statement)

References 17 publications

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“…Broadwell et al [5] proposed a large-scale mixing model and defined as a criterion of the ratio between the chemical reaction time and the turbulent mixing time to characterize the stability of turbulent diffusion flames. The effect of coflow air on the blow-out limit was also investigated [6][7][8][9][10][11][12][13][14][15] and an effective velocity was proposed. The effect of coflow air temperature was also studied [16,17].…”

Section: Introductionmentioning

confidence: 99%

Blow-out limits of nonpremixed turbulent jet flames in a cross flow at atmospheric and sub-atmospheric pressures

Wang

Yoon

et al. 2015

Combustion and Flame

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NomenclatureThese results were compared with results from a wind tunnel under standard atmospheric pressure (100 kPa) in Hefei city (altitude 50 m). The size of the fuel nozzles used in the experiments ranged from 3 to 8 mm in diameter and propane was used as the fuel. It was found that the blow-out limit first increased and then decreased as the fuel jet velocity increased in both pressures, however, the blow-out limit of the air speed of the cross flow was much lower under the sub-atmospheric pressure than that under standard atmospheric pressure with the domain of the blow-out limit in a plot of the air speed of the cross flow in relation to the fuel jet velocity shrank as the pressure decreased. A theoretical model was developed to characterize the blow-out limit of nonpremixed jet flames in a cross flow based on a Damköhler number, defined as the ratio between the mixing time and the characteristic reaction time. A satisfactory correlation was obtained that included the effects of the air speed of the crossflow, fuel jet velocity, nozzle diameter and pressure.

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Section: Introductionmentioning

confidence: 99%

Blow-out limits of nonpremixed turbulent jet flames in a cross flow at atmospheric and sub-atmospheric pressures

Wang

Yoon

et al. 2015

Combustion and Flame

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Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2–Natural Gas–Air Mixtures

Utschick

Sattelmayer

2016

Journal of Engineering for Gas Turbines and Power

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Flashback (FB) and self-ignition in the premixing zone of typical gas turbine swirl combustors in lean premixed operation are immanent risks and can lead to damage and failure of components. Thus, steady combustion in the premixing zone must be avoided under all circumstances. This study experimentally investigates the flame holding propensity of fuel injectors in the swirler of a gas turbine model combustor with premixing of H2–natural gas (NG)–air mixtures under atmospheric pressure and proposes a model to predict the limit for safe operation. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). A cylindrical duct and a window in the swirler made of quartz glass allow the application of optical diagnostics (OH* chemiluminescence and planar laser induced fluorescence of the OH radical (OH-PLIF)) inside the swirler. The fuel–air mixture was ignited with a focused single laser pulse during steady operation. The position of ignition was located inside the swirler in proximity to a fuel injection hole. If the flame was washed out of the premixing zone not later than 4 s after the ignition, the operation point was defined as safe. Operation points were investigated at three air mass flows, three air ratios, two air preheat temperatures (573 K and 673 K), and 40 to 100 percent per volume hydrogen in the fuel composed of hydrogen and natural gas. The determined safety limit for atmospheric pressure yields a similarity rule based on a critical Damköhler number. Application of the proposed rule at conditions typical for gas turbines leads to these safety limits for the A2EV burner: With the TEIs, the swirler can safely operate with up to 80 percent per volume hydrogen content in the fuel at an air ratio of two. With the JIC injector, safe operation at stoichiometric conditions and 95 percent per volume hydrogen is possible.

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Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2-NG-Air-Mixtures

Utschick

Sattelmayer

2016

Volume 4A: Combustion, Fuels and Emissions

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Flashback and self-ignition in the premixing zone of typical gas turbine swirl combustors in lean premixed operation are immanent risks and can lead to damage and failure of components. Thus, steady combustion in the premixing zone must be avoided under all circumstances. This study experimentally investigates the flame holding propensity of fuel injectors in the swirler of a gas turbine model combustor with premixing of H2-NG-air-mixtures under atmospheric pressure and proposes a model to predict the limit for safe operation. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). A cylindrical duct and a window in the swirler made of quartz glass allow the application of optical diagnostics (OH* chemiluminescence and Planar Laser Induced Fluorescence of the OH radical (OH-PLIF)) inside the swirler. The fuel-air-mixture was ignited with a focused single laser pulse during steady operation. The position of ignition was located inside the swirler in proximity to a fuel injection hole. If the flame was washed out of the premixing zone not later than four seconds after the ignition the operation point was defined as safe. Operation points were investigated at three air mass flows, three air ratios, two air preheat temperatures (573 K, 673 K) and 40 to 100 percent per volume hydrogen in the fuel composed of hydrogen and natural gas. The determined safety limit for atmospheric pressure yields a similarity rule based on a critical Damköhler number. Application of the proposed rule at conditions typical for gas turbines leads to these safety limits for the A2EV burner: With the TEIs the swirler can safely operate with up to 80 percent per volume hydrogen content in the fuel at an air ratio of two. With the JIC injector safe operation at stoichiometric conditions and 95 percent per volume hydrogen is possible.

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Stability and Blowout Behavior of Jet Flames in Oblique Air Flows

Cited by 3 publications

References 17 publications

Blow-out limits of nonpremixed turbulent jet flames in a cross flow at atmospheric and sub-atmospheric pressures

Blow-out limits of nonpremixed turbulent jet flames in a cross flow at atmospheric and sub-atmospheric pressures

Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2–Natural Gas–Air Mixtures

Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2-NG-Air-Mixtures

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