A computational study of oscillatory extinction of spherical diffusion flames

Christiansen, Erik W.; Tse, Stephen D.; Law, Chung K.

doi:10.1016/s0010-2180(03)00112-3

“…(42). A similar response was predicted by Christiansen et al [22] in their numerical simulation using detailed chemistry and transport. They found that once the maximum flame temperature drops below the critical value corresponding to the quasi-steady extinction during oscillation, the oscillation cannot recover and extinction occurs.…”

Section: Resultssupporting

confidence: 87%

“…In another study, Christiansen et al [22] simulated a spherical methane-air diffusion flame with detailed chemistry and transport. The parameters used in their work were Le F = 2.3, Le O = 1.9, φ = 13.73, and T = 0 which also lie in the third quadrant of the α 1r − α 2r plane, and they similarly found growing oscillations leading to extinction.…”

Section: Resultsmentioning

confidence: 99%

“…However, the nonlinear analysis of flame dynamics is much more complex in diffusion flames than those of premixed flames, owing to some technical difficulties in analyzing the reaction zone structure. Therefore, up to now, only one theoretical work [18] and a few numerical works [9,[19][20][21][22] have addressed the nonlinear dynamics of diffusion flames. Specifically, Cheatham [18] derived an evolution equation for the perturbation amplitude in a droplet flame by employing a weakly nonlinear theory, and provided a diagram mapping various possible long-time behaviors.…”

Section: Introductionmentioning

confidence: 99%

“…No limit cycle behavior was predicted in the absence of radiative heat loss. Christiansen et al [22] simulated the transient behavior of burner-supported spherical diffusion flames using detailed chemistry and transport. Their results show that, when Da < Da * , the amplitude of oscillations always increased, and eventually led to extinction when the amplitude became too large.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear oscillations in diffusion flames

Wang

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Bechtold

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“…Radiative extinction was observed in microbuoyant burner-supported spherical flames in normal gravity by Yoo et al [10], but these were not truly nonbuoyant flames and a small amount of buoyancy can have a significant impact on flames near extinction. Theoretical work on spherical flames was presented in King [11], Atreya and Agrawal [12], Mills and Matalon [6,13], Christiansen et al [14] and Liu et al [9]. Radiative extinction has also been reported for counterflow flames in microgravity [15].…”

Section: Introductionmentioning

confidence: 99%

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

Santa

¹

,

Chao

²

,

Sunderland

³

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

show abstract

Radiative extinction of gaseous spherical diffusion flames in microgravity

Santa

¹

,

Chao

²

,

Sunderland

³

et al. 2007

Combustion and Flame

View full text Add to dashboard Cite

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

show abstract

A computational study of oscillatory extinction of spherical diffusion flames

Cited by 37 publications

References 13 publications

Nonlinear oscillations in diffusion flames

Nonlinear oscillations in diffusion flames

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

Radiative extinction of gaseous spherical diffusion flames in microgravity

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