The Regime Diagram for Premixed Flame Kernel-Vortex Interactions - Revisited
Title | The Regime Diagram for Premixed Flame Kernel-Vortex Interactions - Revisited PDF eBook |
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Release | 2004 |
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Regimes of flame kernel-vortex (KV) interactions are investigated numerically using a detailed mechanism for hydrogen chemistry. The parametric simulations explore a wide range of conditions that are representative of conditions encountered at various degrees of turbulence intensity. The results show that KV interactions can be classified into five different regimes, which include 1) the laminar kernel regime, 2) the wrinkled kernel regime, 3) the breakthrough regime, 4) the global extinction regime, and 5) the regeneration after global extinction (RGE) regime. With the exception of the last regime, the transition from one regime to another in the order listed corresponds to increasing the vortex size and strength. Operation at the RGE regime reveals interesting dynamics of the flame front that results in reignition or mending of combustion regimes after most of the original kernel has extinguished due to intense straining. Two different types of combustion zones are observed, which correspond to a flamelet structure as well as to more diffuse structures of merged flame segments. A revised regime diagram of the KV interactions is proposed that includes the broader range of KV interactions and incorporate the new RGE regime.
Regimes of Non-Premixed Flame-Vortex Interactions
Title | Regimes of Non-Premixed Flame-Vortex Interactions PDF eBook |
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Pages | 9 |
Release | 2000 |
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Detailed studies of flame-vortex interactions are extremely valuable to improve our understanding of turbulent combustion regimes. Combined experimental and numerical studies have already been performed in the premixed case during previous investigations. Therefore, we decided to carry out a detailed experimental investigation on the regimes observed during interaction of a vortex ring and a non-premixed, diluted, hydrogen/air, laminar counterflow flame. To obtain the needed information, several optical diagnostic techniques have been used, in particular, planar laser-induced fluorescence (PLIF) of acetone to quantify vortex structure and speed, simultaneous OH PLIF and Rayleigh measurements, and simultaneous OH PLIF and particle-imaging velocimetry (PIV) measurements. A post-processing of the results combined with direct simulations using detailed chemistry and transport models to check the quality of the postprocessing procedures has led to the construction of a spectral interaction diagram. Eight interaction types were found, emphasizing the relative importance of competing physical phenomena such as straining, curvature, wrinkling, roll-up, and extinction. In particular, we observe two different types of extinction, one due to the combined action of curvature and straining, and the other purely due to straining effects. It was also observed that many vortices are too small or dissipate too rapidly to influence the flame. In other cases, the vortex ring can lead to the formation of pockets of oxidizer burning in the fuel part of the domain. These regimes and the limits between them have important implications for the modeling of turbulent non-premixed combustion.
A Laminar Vortex Interacting with a Premixed Flame
Title | A Laminar Vortex Interacting with a Premixed Flame PDF eBook |
Author | Wm L. Roberts |
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Release | 1992 |
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Interaction of a Vortex and a Premixed Flame
Title | Interaction of a Vortex and a Premixed Flame PDF eBook |
Author | Christopher J. Rutland |
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Release | 1989 |
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Vortex-flame Interactions in Opposing-jet Premixed Flames
Title | Vortex-flame Interactions in Opposing-jet Premixed Flames PDF eBook |
Author | V. R. Katta |
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Release | 2000 |
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Investigation of a Spark Ignition Flame Kernel Interacting with a Laminar Vortex Toroid
Title | Investigation of a Spark Ignition Flame Kernel Interacting with a Laminar Vortex Toroid PDF eBook |
Author | Yin Xiong |
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Pages | 157 |
Release | 2001 |
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Keywords: flame kernel, turbulent combustion, vortex, Lewis number.
The Effect of Stoichiometry on Vortex Flame Interactions
Title | The Effect of Stoichiometry on Vortex Flame Interactions PDF eBook |
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Pages | 5 |
Release | 1999 |
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The interaction of a vortex pair with a premixed flame serves as an important prototype for premixed turbulent combustion. In this study, the authors investigate the interaction of a counter-rotating vortex pair with an initially flat premixed methane flame. The authors focus on characterizing the mechanical nature of the flame-vortex interaction and on the features of the interaction strongly affected by fuel equivalence ratio. The authors compare computational solutions obtained using a time-dependent, two-dimensional adaptive low Mach number combustion algorithm that incorporates GRI-Mech 1.2 for the chemistry, thermodynamics and transport of the chemical species. The authors find that the circulation around the vortex scours gas from the preheat zone in front of the flame, making the interaction extremely sensitive to equivalence ratio. For nearly stoichiometric cases, the peak mole fraction of CH across the flame is relatively insensitive to the vortex whereas for richer flames they observe a substantial and rapid decline in the peak CH mole fraction, commencing early in the flame-vortex interaction. The peak concentration of HCO is found to correlate, in both space and time, with the peak heat release across a broad range of equivalence ratios. The model also predicts a measurable increase in C2H2 as a result of interaction with the vortex, and a marked increase in the low temperature chemistry activity.