Influences of stretch and curvature on the temperature of stretched cylindrical diffusion flames

Suenaga, Yosuke; Yanaoka, Hideki; Momotori, Daisuke

doi:10.1299/jtst.2016jtst0028

Cited by 4 publications

(4 citation statements)

References 19 publications

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“…In our study on steady stretched cylindrical diffusion flames, which was conducted under the same experimental conditions, the flame temperature decreased with increasing flame curvature (that is, the flame was weakened). In contrast, the flame temperature increased with an increase in the flame stretch rate (that is, the flame was strengthened) [8]. The flame stretch rate is proportional to the velocity gradient.…”

Section: Frequency Characteristics Of the Flame Luminositymentioning

confidence: 98%

“…The burner was identical to that used in our studies on steady stretched cylindrical diffusion flames [7,8]. The coordinate system and flame image are shown in Figs.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…To predict the combustion behavior of a turbulent diffusion flame, it is necessary to understand the influence of velocity fluctuation on a laminar diffusion flame that is simultaneously influenced by stretching and curvature. Using a steady stretched cylindrical diffusion flame, we have experimentally studied the influence of stretch and curvature on flame temperature and extinction [7,8]. The present study…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Response of Stretched Cylindrical Diffusion Flame to Sinusoidal Oscillation of Air Flow Velocity

Suenaga¹,

Yanaoka²,

Kikuchi³

et al. 2017

JMEA

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An experimental study investigated the characteristics of a stretched cylindrical diffusion flame, with a convex curvature with respect to the air stream, in response to periodic air flow velocity oscillation. The fuel was methane diluted with nitrogen, and the oxidizer air. The oscillation frequency was varied from 5 to 250 Hz. The results are summarized as follows. Though the fluctuation amplitude of the air stream velocity gradient was constant with respect to the frequency, the amplitude of the fuel stream increased. The fluctuation amplitude of the flame radius changed quasi-steadily from 5 to 25 Hz, and decreased with increasing frequency in the frequency range greater than 50 Hz. The flame luminosity did not respond quasi-steadily at 5 Hz, and the oscillation amplitude of flame luminosity was less than that of a steady flame, over the same velocity fluctuation range. The oscillation amplitude of luminosity peaked at 50 Hz, and was greater than that of a steady flame. It is considered that this complex change in flame luminosity with respect to frequency was closely related to the phase difference in the respective time variations in the ratio of flame thickness to radius, the velocity gradients of the air and fuel streams, and the magnitude of these values, with the ratio of flame thickness to radius related to the flame curvature effect, the velocity gradient of the air stream correlated to the flame stretch effect, and the velocity gradient of the fuel stream impacting the fuel transportation.

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Section: Frequency Characteristics Of the Flame Luminositymentioning

confidence: 98%

“…The burner was identical to that used in our studies on steady stretched cylindrical diffusion flames [7,8]. The coordinate system and flame image are shown in Figs.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Response of Stretched Cylindrical Diffusion Flame to Sinusoidal Oscillation of Air Flow Velocity

Suenaga¹,

Yanaoka²,

Kikuchi³

et al. 2017

JMEA

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“…Laminar tubular flames are highly stretched and curved similar to turbulent flames and thus allow for isolating and studying stretch and curvature effects in flames [1]. In the past, tubular flames have been studied at 1 bar to understand the effect of stretch and curvature on preferential diffusion in hydrogen [2][3][4][5][6][7][8][9][10][11][12] and hydrocarbon flames [13] in premixed [2][3][4][5], non-premixed [6][7][8][9][10][11][13][14][15][16], and partially premixed configurations [12]. However, at high pressures, which are also characteristic of real-life combustors, minimal literature exists in the field of premixed tubular flames [17] and nothing in the field of non-premixed tubular diffusion flames.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of the Structure and NO Emission Characteristics of N2- and CO2-Diluted Tubular Diffusion Flames

2019

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The structure of methane/air tubular diffusion flames with 65 % fuel dilution by either CO2 or N2 is numerically investigated as a function of pressure. As pressure is increased, the reaction zone thickness reduces due to decrease in diffusivities with pressure. The flame with CO2-diluted fuel exhibits much lower nitrogen radicals (N, NH, HCN, NCO) and lower temperature than its N2-diluted counterpart. In addition to flame structure, NO emission characteristics are studied using analysis of reaction rates and quantitative reaction pathway diagrams (QRPDs). Four different routes, namely the thermal route, Fenimore prompt route, N2O route, and NNH route, are examined and it is observed that the Fenimore prompt route is the most dominant for both CO2- and N2-diuted cases at all values of pressure followed by NNH route, thermal route, and N2O route. This is due to low temperatures (below 1900 K) found in these highly diluted, stretched, and curved flames. Further, due to lower availability of N2 and nitrogen bearing radicals for the CO2-diluted cases, the reaction rates are orders of magnitude lower than their N2-diluted counterparts. This results in lower NO production for the CO2-diluted flame cases.

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Response of a stretched cylindrical diffusion flame to a sinusoidal velocity oscillation of air stream

Suenaga

Yanaoka

Kikuchi

et al. 2017

Transactions of the JSME (In Japanese)

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Experimental study was performed to reveal the response characteristics of a stretched cylindrical diffusion flame to sinusoidal oscillation of air flow velocity. The cylindrical flame used in this study has a convex curvature with respect to air stream and is formed in air stream. The fuel is methane, diluted with nitrogen, and the oxidizer is air. Oscillation frequency f is varied from 5 Hz to 250 Hz. Velocity at the outlet of air supplying nozzle was changed sinusoidally with four speakers.Velocity at the fuel nozzle outlet was kept constant. The air velocity at the nozzle outlet is measured using particle image velocimetry. Flame radius rf, flame thickness δ, and flame luminosity Lf are obtained by using high speed video camera. is associated with the flame curvature effect, ga which affects the flame stretch effect, and gf which impacts fuel transport.

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Influences of stretch and curvature on the temperature of stretched cylindrical diffusion flames

Cited by 4 publications

References 19 publications

Response of Stretched Cylindrical Diffusion Flame to Sinusoidal Oscillation of Air Flow Velocity

Response of Stretched Cylindrical Diffusion Flame to Sinusoidal Oscillation of Air Flow Velocity

Numerical Study of the Structure and NO Emission Characteristics of N2- and CO2-Diluted Tubular Diffusion Flames

Response of a stretched cylindrical diffusion flame to a sinusoidal velocity oscillation of air stream

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