Faster flicker of buoyant diffusion flames by weakly rotatory flows

Yang, Tianjun; Zhang, Peng

doi:10.1007/s00162-023-00671-0

Cited by 3 publications

(15 citation statements)

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“…The intensity of the swirling flow is measured by a dimensionless parameter 𝑅 = 𝑈/𝑈 , which has similarity with the swirl number in defining the ratio of the swirling quantity and the axial jet quantity [50]. The notations of all quantities are consistent with those in the previous study [32].…”

mentioning

confidence: 76%

“…and the chemical reaction characteristic time τ c can be determined by the fastest reaction. Based on the large Damköhler number approximation, the previous computational works [32,40,56] were formulated and carried out on the computational platform of FDS.…”

Section: Finite Rate Chemistry Effects On Flame Flickermentioning

confidence: 99%

“…By applying the criterion of Γ * (τ) = constant for a vortex shedding process [31], they obtained a generalized scaling law of the flame flickering frequency and validated it with the previous scaling laws and data from existing literature for Fr ≪ 1 and Ri ≫ 1. Recently, Yang and Zhang [32] studied the vortex dynamics in flickering buoyant diffusion flames in weakly swirling flows and extended a vortex-dynamical scaling theory for the flame flicker with an external swirl. Dynamical behaviors of multiple flickering flames have recently attracted much research interest.…”

Section: Introductionmentioning

confidence: 99%

“…The finite rate chemistry (OFC) of the one-step methane/air reaction was used and expatiated in Section 3.1. More details of the computational setups can refer to our recent work [32] on buoyant diffusion flames in weakly swirling flows. In addition, previous computational works [40,56] have proven the reliability of this computational platform in successfully reproducing various synchronization modes in dual and triple flickering flame systems.…”

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confidence: 99%

“…We carried out domain-and mesh-independence studies and adopted a uniform structure mesh of 160 × 160 × 240 for the parametric studies to ensure high accuracy with reasonable computational cost. Our previous study [32,56] shows that the mesh refinement (each grid has ∆ x = ∆ ŷ = ∆ ẑ = 10 −2 ) is sufficient to capture the essential features of the buoyancy-induced flicker of a laminar diffusion flame. Particularly, the central region (8D × 8D × 12D with ∆ x = ∆ ŷ = ∆ ẑ = 5 × 10 −3 ) is further refined in the present cases to analyze closely the flame lift-off behavior due to the emergence of local flame extinction [57].…”

mentioning

confidence: 99%

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Dynamical Behavior of Small-Scale Buoyant Diffusion Flames in Externally Swirling Flows

Yang,

Ma,

Zhang

2024

Symmetry

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This study computationally investigates small-scale flickering buoyant diffusion flames in externally swirling flows and focuses on identifying and characterizing various distinct dynamical behaviors of the flames. To explore the impact of finite rate chemistry on flame flicker, especially in sufficiently strong swirling flows, a one-step reaction mechanism is utilized for investigation. By adjusting the external swirling flow conditions (the intensity R and the inlet angle α), six flame modes in distinct dynamical behaviors were computationally identified in both physical and phase spaces. These modes, including the flickering flame, oscillating flame, steady flame, lifted flame, spiral flame, and flame with a vortex bubble, were analyzed from the perspective of vortex dynamics. The numerical investigation provides relatively comprehensive information on these flames. Under the weakly swirling condition, the flames retain flickering (the periodic pinch-off of the flame) and are axisymmetric, while the frequency nonlinearly increases with the swirling intensity. A relatively high swirling intensity can cause the disappearance of the flame pinch-off, as the toroidal vortex sheds around either the tip or the downstream of the flame. The flicker vanishes, but the flame retains axisymmetric in a small amplitude oscillation or a steady stay. A sufficiently high swirling intensity causes a small Damköhler number, leading to the lift-off of the flame (the local extinction occurs at the flame base). Under the same swirling intensity but large swirling angles, the asymmetric modes of the spiral and vortex bubble flames were likely to occur. With R and α increasing, these flames exhibit axisymmetric and asymmetric patterns, and their dynamical behaviors become more complex. To feature the vortical flows in flames, the phase portraits are established based on the velocity information of six positions along the axis of the flame, and the dynamical behaviors of various flames are presented and compared in the phase space. Observing the phase portraits and their differences in distinct modes could help identify the dynamical behaviors of flames and understand complex phenomena.

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mentioning

confidence: 76%

Section: Finite Rate Chemistry Effects On Flame Flickermentioning

confidence: 99%