Characteristics of the Flame Propagating through a Mixture Flow with Periodic Concentration Fluctuation (Effects of Concentration Fluctuation Range on Flame Characteristics)

Suenaga, Yosuke; Kitano, Michio; Yanaoka, Hideki; Fujita, Naotake

doi:10.1299/kikaib.71.1190

Cited by 6 publications

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“…1,2012 variation from lean to rich and vice versa. These double cycles were observed in the experiment by Suenaga et al (17) , although the single cycle is seen instead of the double cycles even in the case of the lean rich crossover case in analysis done by Lauvergne and Egolfopoulos (8) at higher oscillation frequency.…”

Section: Flame Responsementioning

confidence: 69%

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Numerical Investigation of a Flame Response to the Fuel Concentration Oscillation in Stagnating Laminar Premixed Methane/Air Flames

Rahman

Yokomori²,

Ueda³

2012

JTST

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Responses of the premixed methane/air mixture flames under equivalence ratio oscillations were numerically investigated assuming axi-symmetric stagnation flow fields. The flame motion was numerically investigated at three different oscillation frequencies (10, 20 and 50 Hz) and with three oscillation cases namely: lean case, rich case and lean rich crossover case. Methane/air mixture with equivalence ratio oscillation was issued from the burner exit with 1.0 m/s uniform velocity profile. The effects of frequency and amplitude of the equivalence ratio oscillation were discussed. The amplitude of the equivalence ratio oscillation is attenuated between the burner exit and the upstream edge of the preheat zone. The attenuation is much significant for higher frequency. The amplitude of the flame temperature oscillation attenuates following the attenuation of the equivalence ratio oscillation. The flame location makes the closed cycle around the flame location of correspond equivalence ratio in the steady state condition. The formation of the cycle can be explained by the back support effect. It was further demonstrated that, the back support effect influences the dynamic response of the flame location, in that, the direction of the cycles of the dynamic response in the lean case and the rich case are different. Furthermore, the time variation of the flame location plays a significant effect to the flame displacement speed.

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Section: Flame Responsementioning

confidence: 69%

“…Unfortunately the consumption speed Jacque lamina which pertur al. (17) p freque It equiva diffusi respon flame.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of a Flame Response to the Fuel Concentration Oscillation in Stagnating Laminar Premixed Methane/Air Flames

Rahman

Yokomori²,

Ueda³

2012

JTST

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“…The characteristics of a flame propagating through a mixture with a periodic concentration fluctuation were also investigated (5) - (7) . Time variations of burning velocity, burnt gas temperature and burnt gas compositions (CO, H 2 , CO 2 , NOx) were examined with a stagnationflow burner, which was devised to fluctuate the mixture concentration periodically only in the direction of flow without varying the burner outlet velocity, and the following results were obtained.…”

Section: Introductionmentioning

confidence: 99%

Response of a Cylindrical Premixed Flame to Periodic Concentration Fluctuation

Takahashi

Suenaga

Kitano

et al. 2006

JSME international journal. Ser. B, Fluids and thermal engineer

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The response of a cylindrical premixed flame to periodic concentration fluctuation was investigated. The flame was formed in a porous cylinder by percolating a lean methane-air mixture uniformly through the cylinder wall. The burner used here was devised so as to cause fluctuations of the mixture concentration (equivalence ratio) only in the radial direction of the flow (vertically to the cylindrical flame surface) without varying the flow field. Using this burner, the time variations of burning velocity, burnt gas temperature and flame luminosity were measured for the mixture in a range of fluctuation frequencies from 3 to 50 Hz, and the results were examined from the viewpoint of flame curvature effects. The results show that the variation width of the burning velocity of the dynamic flame is larger than that of the static flame in the concentration range corresponding to the fluctuation. Burnt gas temperature and flame luminosity also exhibit similar tendencies. The magnification ratio of the variation width depends on the flame curvature, and a large flame curvature results in a sustainable flame, even for a mixture leaner than the flammability limit of the static flame.

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“…In contrast with numerical analysis, little empirical research has been reported, because it is difficult to make experimental apparatuses that can oscillate the fuel concentration without inducing velocity oscillation. Suenaga et al (2005Suenaga et al ( , 2010 revealed experimentally that the burning velocity and flame luminosity near the lean flammability limit could become lower under concentration oscillation than those under the steady-state condition.…”

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confidence: 99%

Quasi-steady state to non-steady state transition criterion of laminar stagnating lean premixed flame with fuel concentration oscillation

Kawasaki

Kashiwagi²,

Yokomori³

et al. 2016

Mechanical Engineering Letters

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Lean premixed combustion is important in developing combustors with higher efficiency and lower NOx emission. However, lean premixed combustion involves technical issues that have not been solved yet, such as combustion instabilities. Lieuwen and Zinn (1998) suggested that equivalence ratio oscillation plays a key role in driving instability in low-NOx-emission lean premixed combustors. Lieuwen et al. (2001) showed that instabilities of lean premixed combustion result from a feedback process between heat release, acoustic pressure and equivalence ratio oscillations. Cho and Lieuwen (2005) analyzed the flame response to equivalence ratio perturbations and showed that the heat release response is controlled by the superposition of three disturbances: heat of reaction, flame speed and flame area. These disturbances are directly and indirectly generated by equivalence ratio oscillation. Prior research has shown that the equivalence ratio oscillation, that is, the fuel concentration oscillation, plays a key role in the instability of low-emission lean premixed combustion.The effect on flame motion of fuel concentration oscillation has been numerically investigated. Lauvergne and Egolfopoulos (2000) showed that the flame response is quasi-steady for low-frequency oscillation in mixture composition, whereas the response is substantially attenuated by diffusion at high frequencies. Marzouk et al. (2000) suggested that flame subject to variation in stoichiometric-to-lean equivalence ratio is intensified by a back support effect, which is the result of heat transport from the burnt gas region. Rosdzimin et al. (2012) showed that the motion in flame location create a closed cycle around the location of the flame under the corresponding equivalence ratio in the steady- AbstractThe criterion for transition from a quasi-steady state to a non-steady state of laminar stagnating lean premixed flame in the presence of oscillation in fuel concentration is discussed experimentally. Two types of mixtures with different Lewis numbers are examined: lean methane/air and lean propane/air mixtures. Sinusoidal oscillation in fuel concentration is effected by an oscillator with two cylinder-piston units that supply leaner and richer mixtures alternately. The flame response under fuel concentration oscillation is measured as a function of frequency. The frequency of fuel concentration oscillation varies within 2-20 Hz, and the burner exit velocity varies within 0.6-1.1 m/s. For both mixtures, oscillator characteristics cause the amplitude of oscillation of the flame position to increase with frequency. The increase in amplitude becomes less sharp as frequency increases further. In the present study, two additional Strouhal numbers, one based on heat transfer and another based on mass transfer, are newly introduced in addition to the ordinary Strouhal number which is based on momentum transfer. When any of these Strouhal numbers exceeds unity, the increase in the amplitude starts to fall off. This indicates that the three Strouhal numbers p...

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Characteristics of the Flame Propagating through a Mixture Flow with Periodic Concentration Fluctuation (Effects of Concentration Fluctuation Range on Flame Characteristics)

Cited by 6 publications

References 0 publications

Numerical Investigation of a Flame Response to the Fuel Concentration Oscillation in Stagnating Laminar Premixed Methane/Air Flames

Numerical Investigation of a Flame Response to the Fuel Concentration Oscillation in Stagnating Laminar Premixed Methane/Air Flames

Response of a Cylindrical Premixed Flame to Periodic Concentration Fluctuation

Quasi-steady state to non-steady state transition criterion of laminar stagnating lean premixed flame with fuel concentration oscillation

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