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

Puri, Ishwar K.; Aggarwal, Suresh K.; Ratti, Stefano; Azzoni, Riccardo

doi:10.1016/s0010-2180(00)00201-7

Cited by 34 publications

(15 citation statements)

References 31 publications

(24 reference statements)

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“…However, these simple calculations extract the essence of the flame structure in an easy manner. The results are not dissimilar to the detailed triple flame calculations by Puri et al (32) The proposed model is also expected to be applicable to turbulent lifted nonpremixed flame.…”

Section: Resultssupporting

confidence: 59%

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Noda

Yamamoto

2006

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

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The flame base structures of laminar lifted flames are numerically investigated in order to develop a model of triple flame applicable to the flamelet model. The lifted flames formed in the downstream expanded duct developed by Kioni et al.(1) are calculated systematically in terms of the fuel concentration gradient at the inlet using a variant of the HSMAC method, modified so as to deal with variations of density. The triple flame is formed at the flame base of lifted nonpremixed flame for every case, even the case which does not initially have partial mixing. The diffusion flame appears to be supported by the enhancement of the surrounding premixed flames, resulting in a temperature rise. All scalar quantities along the premixed flames of the triple flame decline along a similar profile in mixture fraction space, and scalar quantities in the region surrounded by the premixed flames are almost completely conserved. On the basis of the results, we developed a model of triple flame that is applicable to the flamelet model. In the model, the region without reaction upstream of the flame base is referred to as the unburned region (frozen flow structure region), followed by the transition region outside the premixed flames, in which the flame changes from the frozen structure to the fully burning diffusion structure. The region surrounded by the premixed flames is referred to as the triple flame structure region. The region following the triple flame structure region is the fully burning diffusion flame structure region.

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Section: Resultssupporting

confidence: 59%

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Noda

Yamamoto

2006

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

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“…Subsequently, there has been significant interest in the study of these flames [2][3][4][5][6][7][8][9][10][11][12][13] due to their fundamental and practical relevance, especially with regards to nonpremixed flame stabilization, turbulent combustion, fire safety, autoignition, and flame spread. While the previous studies have examined the detailed structure and stability of these flames, they have not examined the emission characteristics in detail.…”

Section: Introductionmentioning

confidence: 99%

Effect of multistage combustion on NOx emissions in methane–air flames

Briones

Som

Aggarwal

2007

Combustion and Flame

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“…Investigations of axisymmetric partially premixed flames have been reported by Bennet et al [36]. Recently, we have investigated lifted triple flames and addressed issues related to flame stabilization [7]. We found that both lifted and burner-stabilized flames exhibit remarkable similarity with respect to the shapes and separation distances regarding the three reaction zones.…”

Section: Introductionmentioning

confidence: 50%

“…More quantitative validations of the computational model in terms of velocity, temperature, and major species mole fractions have been provided in our earlier investigations on steady partially premixed flames [5,7,[25][26][27]. Figure 3 depicts the flame structures in terms of heat release rates and velocity vectors for 0-and 1-g partially premixed flames established at φ = 2.0, V reac = 30 cm s -1 , and without any coflow.…”

Section: Validation: Comparison With Measurements For Steady Flamesmentioning

confidence: 93%

“…The first is to examine the effects of coflow on the structure and stability of normal-and zero-gravity partially premixed flames established on a Wolfhard-Parker slot burner, which is a geometry that we have used extensively to characterize PPFs [7,[17][18]. Here the flame response to inherent and forced perturbations and the associated flame-vortex interactions are also investigated.…”

Section: Unsteady Partially Premixed Flamesmentioning

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

Cited by 34 publications

References 31 publications

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Effect of multistage combustion on NOx emissions in methane–air flames

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

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