Response of a Cylindrical Premixed Flame to Periodic Concentration Fluctuation

Takahashi, Yoichi; Suenaga, Yosuke; Kitano, Michio; Kudo, Megumi

doi:10.1299/jsmeb.49.1307

Cited by 9 publications

(6 citation statements)

References 9 publications

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“…As a basic study of the local structure of a turbulent flame, we have made some studies of a counter flow type cylindrical flame that stretches in the axial direction (5)- (8) . In a study on cylindrical diffusion flames, we performed experiments using propane and methane as fuels, nitrogen as a diluent of fuel, and air as an oxidizer.…”

Section: Introductionmentioning

confidence: 99%

Development of Ultra-Micro Combustor Using Cylindrical Flames

Suenaga

Kitano

Yanaoka

2011

JTST

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The purpose of this study is to develop an ultra-micro combustor that uses two types of coaxial cylindrical flames, rich premixed flame and diffusion flame. The combustor consists of inner and outer porous tubes, and rich propane-air mixture and air issued, respectively, through the inner tube outwardly and through the outer tube inwardly, forming a cylindrical stagnation plane sandwiched by the inner rich premixed flame and the outer diffusion flame. Petal type flame was also observed in the downstream of the cylindrical flames. Keeping the equivalence ratio φ i and flow rate q i of the rich mixture constant, air flow rate q a was varied. The O 2 and CO concentrations and temperature of the burnt gas were measured, and heat loss rate η hl and combustion intensity L were evaluated. The obtained results are described as follows. (1)The relation curve of η hl with the overall equivalence ratio φ all , which is evaluated from the total flow rate of the fuel and the air, has a minimum value.(2)The relation curve of the minimum value of η hl with L has a minimum value. (3) The CO concentration of the burnt gas increases as q a is increased because of local extinction of the petal type flame. (4)When q a is increased further, petal type flame is also extinguished. After that, the O 2 concentration increases and the CO concentration decreases.

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Section: Introductionmentioning

confidence: 99%

Development of Ultra-Micro Combustor Using Cylindrical Flames

Suenaga

Kitano

Yanaoka

2011

JTST

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“…The extinction limits are extended as a result of the amplitude attenuation caused by the diffusion and they depend upon the mean value and frequency amplitude of the equivalence ratio oscillation (5) . Moreover, increase in the oscillation amplitude of the burning velocity, burnt gas temperature, burnt gas composition and flame luminosity with equivalence ratio oscillations have been observed experimentally (7), (10)- (12) . Later, the back support effect introduced in Ref.…”

Section: Introductionmentioning

confidence: 86%

The Response of a Conical Laminar Premixed Flame to Equivalence Ratio Oscillations in Rich Conditions

Rahman

Yokomori²,

Ueda³

2013

JTST

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Responses of conical premixed methane/air mixture flames with equivalence ratio oscillations were numerically investigated at three different oscillation frequency regimes; low, medium and high (10, 50 and 150 s -1 ) under a rich condition.One-step and two-step reaction mechanism have been investigated. The pre-exponential factors for the one-step and two-step reaction mechanism were calibrated at minimum and maximum equivalence ratio of this study, Ø = 1.1 and 1.5, by comparing the flame length of the numerical results with the experimental results. The two-step reaction mechanism predicted well the variation in the flame shape under a steady state condition with equivalence ratio variations while the one-step reaction mechanism failed to predict the variation in the flame shape especially under the near rich flammability limit condition. This is because of the CO formation inclusion in the two-step reaction mechanism. The effects of the equivalence ratio oscillation frequency towards flame dynamics were discussed. The amplitude of the flame tip movement attenuates following the attenuation of the equivalence ratio oscillation towards the downstream direction at high oscillation frequency. The dynamic response of the flame tip for low, medium and high oscillation frequency regimes shows interesting behavior. The quasi-steady manner of the flame tip movement was observed at the low frequency regime. In the medium and high frequency regime cases, we found that the attenuation of the flame tip motion is affected by the wrinkling of the flame surface in addition to the attenuation of the equivalence ratio oscillation amplitude. Moreover, an increase in the number of wrinkles as the equivalence ratio oscillation frequency is increased induces large attenuation of the flame tip oscillation amplitude. Furthermore, we found that the period of the equivalence ratio oscillation, T and the convective transport time, τ control the flame response in that ⁄ , is a controlling parameter of the conical flame response in quasi-steady ⁄ 1.0 or unsteady ⁄ 1.0 manner.

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“…Experimental studies with a stagnation flow were conducted by the authors (Suenaga et al, 2003a(Suenaga et al, , 2003b(Suenaga et al, , 2007(Suenaga et al, , 2010Takahashi et al, 2005Takahashi et al, , 2006 and Tomita et al (2015). The authors studied the response of a stretched flat premixed flame formed in a wall stagnation flow and a stretched cylindrical premixed flame formed in a porous metal cylinder to periodic concentration fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Dynamic response of wall-stagnating lean methane-air premixed flame to equivalence ratio oscillation

Suenaga

Yanaoka

Kikuchi

et al. 2018

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In order to clarify the response characteristics of a lean methane-air premixed flame to equivalence ratio oscillation from actual measured values of the burning velocity, we developed a new burner with a wall-stagnating flow that allowed measurement of the flow field by using particle image velocimetry (PIV). To create fluctuations in the equivalence ratio only in the direction of flow without varying the velocity field, fuel and air flow rates were controlled by alternately vibrating two sets of loudspeakers. Burning velocity Su was calculated from the measured unburnt gas velocity ug and flame moving velocity uf. ug at the front edge of the flame was measured by PIV. uf was obtained using a high-speed video camera. For an oscillation with a mean equivalence ratio of 0.85, amplitude of 0.05 and frequency f ranging from 5 to 50 Hz, the following results were obtained: (1) The oscillation amplitude of the flame position changed quasi-steadily in the low frequency range, decreasing with increasing f in the frequency range greater than 40 Hz. (2) The oscillation amplitude of the burning velocity of dynamic flame ΔSud obtained by PIV measurement increased with respect to f, and reached maximum at 40 Hz. The maximum value became greater than that of the static flame ΔSus, over the same equivalence ratio range. This tendency was similar to the result obtained by approximating the flow field by a potential flow. (3) The frequency characteristics of the oscillation amplitude ratio of the burning velocity ΔS (= ΔSud/ΔSus) qualitatively correspond to the results ΔS(p) (= ΔSud(p)/ΔSus(p)) obtained by approximating the flow field by the potential flow. However, ΔS is quantitatively larger than ΔS(p), and the difference between ΔS and ΔS(p) is large in the high frequency range. This is because the approximation of the flow field by the potential flow underestimates the oscillation amplitude of the unburnt gas velocity, and the degree of the underestimation becomes noticeable in the high frequency range.

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Response of a Cylindrical Premixed Flame to Periodic Concentration Fluctuation

Cited by 9 publications

References 9 publications

Development of Ultra-Micro Combustor Using Cylindrical Flames

Development of Ultra-Micro Combustor Using Cylindrical Flames

The Response of a Conical Laminar Premixed Flame to Equivalence Ratio Oscillations in Rich Conditions

Dynamic response of wall-stagnating lean methane-air premixed flame to equivalence ratio oscillation

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