Gravity effects on steady two-dimensional partially premixed methane–air flames

Shu, Zhuang; Choi, Chun W.; Aggakwal, Suresh K.; Katta, ViswanthH R.; Puri, Ishwar K.

doi:10.1016/s0010-2180(98)00149-7

Cited by 45 publications

(38 citation statements)

References 18 publications

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“…An implicit algorithm is employed to solve the unsteady gas-phase equations. The simulation method is described in detail elsewhere [12,15,24,25]. The numerical model solves the time-dependent governing equations for a two-dimensional reacting flow.…”

Section: Numerical Modelmentioning

confidence: 99%

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Puri

Aggarwal

Ratti

et al. 2001

Combustion and Flame

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Section: Numerical Modelmentioning

confidence: 99%

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Puri

Aggarwal

Ratti

et al. 2001

Combustion and Flame

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“…(1) represents the mass, momentum, species, or energy conservation equations depending on the variable used for φ. The transport coefficients Γ φ and the source term S φ appearing in the governing equations are provided in our previous publication [6]. A body force term due to gravitational field is included in the axial momentum equation.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…In a subsequent study [6], we investigated steady partially premixed flames established under normal and zero gravity conditions. The results showed that the inner premixed reaction was only mildly affected by gravity, whereas the outer nonpremixed reaction zone was strongly influenced by gravity.…”

Section: Introductionmentioning

confidence: 99%

“…While the fuel consumption chemistry producing CO and H 2 dominated the inner premixed reaction zone, that in the outer nonpremixed reaction zone was characterized by the CO and H 2 oxidation chemistry. The comparison of predicted and measured flames indicated a direct correlation between the predicted heat release rate contours and the experimentally-obtained C * 2 -chemiluminescent emission contours.In a subsequent study [6], we investigated steady partially premixed flames established under normal and zero gravity conditions. The results showed that the inner premixed reaction was only mildly affected by gravity, whereas the outer nonpremixed reaction zone was strongly influenced by gravity.…”

mentioning

confidence: 99%

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Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

Aggarwal

2009

International Journal of Spray and Combustion Dynamics

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In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs) subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H 2 , which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter V R , defined as the ratio of coflow velocity to jet velocity. For V R ≤ 1 (low coflow velocity regime), the structures of both 0-and 1-g flames are strongly sensitive to changes in V R , while they are only mildly affected by coflow in the high coflow velocity regime (V R > 1). In addition, the spatio-temporal characteristics of the 0-and 1-g flames are markedly different in the first regime, but are essentially similar in the second regime. A more significant difference in the first regime between these flames is the presence of a flow instability that manifests itself through the self-excited oscillations of the 1-g flame and the concomitant flickering of the nonpremixed reaction zone. For V R ≤ 1, as the coflow velocity is increased, the oscillation amplitude decreases and the oscillation frequency increases, both of which are in accord with previous experimental and International journal of spray and combustion dynamics · Volume . 1 · Number . 3 . 2009 -pages 339-364 339 1 email: ska@uic.edu computational results concerning 1-g jet diffusion flames. The modified conserved scalar approach is found to be effective in characterizing the flame structure and developing state relationships for both steady and unsteady partially premixed flames. This is demonstrated by the fact that the temperature as well as the major and minor species profiles follow similar state relationships in terms of the modified mixture fraction for the 0-and 1-g flames, even though ...

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“…Consequently, radiation heat transfer becomes significantly more important in microgravity than in normal earth gravity. Although the enhanced importance of radiation heat loss in microgravity has been recognized [9], adequate quantitative understanding of the effects of thermal radiation transfer on laminar coflow diffusion flames is still lacking. A very recent numerical study by Kong and Liu [10] demonstrated that radiation transfer in microgravity laminar coflow methane/air diffusion flame can be so important that the flame temperature is lowered by more than 800 K due to radiation heat loss and the flame experiences partial extinction in the centerline region under certain conditions of their study.…”

Section: Introductionmentioning

confidence: 99%

The Importance of Thermal Radiation Transfer in Laminar Diffusion Flames at Normal and Microgravity

Liu

Smallwood

Kong

2010

Proceeding of the 6th International Symposium on Radiative Transfer

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Gravity effects on steady two-dimensional partially premixed methane–air flames

Cited by 45 publications

References 18 publications

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

The Importance of Thermal Radiation Transfer in Laminar Diffusion Flames at Normal and Microgravity

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