Effect of the fuel-air flow velocity on heat release rate of swirling non-premixed methane flames

Wang, Kuanliang; Li, Fēi; Zou, Pengfei; Lin, Xin; Mao, Ronghai; Yu, Xilong

doi:10.1016/j.ast.2019.105465

Cited by 23 publications

(2 citation statements)

References 27 publications

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“…The inner recirculation zone

is formed by vortex breakdown in the central region. The outer recirculation zone

is formed by the strong swirling effects and confinement, leading to continuous reverse flow [ 48 ]. These two zones carrying hot burnt gas from downstream to upstream significantly influence flame stabilization.…”

Section: Resultsmentioning

confidence: 99%

Entropy: An Inspiring Tool for Characterizing Turbulence–Combustion Interaction in Swirling Flames via Direct Numerical Simulations of Non-Premixed and Premixed Flames

Su,

Liu,

Xiao

et al. 2023

Entropy

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This article focuses on entropy generation in the combustion field, which serves as a useful indicator to quantify the interaction between turbulence and combustion. The study is performed on the direct numerical simulations (DNS) of high pressure non-premixed and premixed swirling flames. By analyzing the entropy generation in thermal transport, mass transport, and chemical reactions, it is found that the thermal transport, driven by the temperature gradient, plays a dominant role. The enstrophy transport analysis reveals that the responses of individual terms to combustion can be measured by the entropy: the vortex stretching and the dissipation terms increase monotonically with the increasing entropy. In high entropy regions, the turbulence behaves as the “cigar shaped” state in the non-premixed flame, while as the axisymmetric state in the premixed flame. A substantial increase in the normal Reynolds stress with the entropy is observed. This is due to the competition between two terms promoted by the entropy, i.e., the velocity–pressure gradient correlation term and the shear production term. As a result, the velocity–pressure gradient correlation tends to isotropize turbulence by transferring energy increasingly from the largest streamwise component to the other smaller normal components of Reynolds stress and is dominated by the fluctuating pressure gradient that increases along the entropy. The shear production term increases with the entropy due to the upgrading alignment of the eigenvectors of strain rate and Reynolds stress tensors.

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“…The inner recirculation zone

is formed by vortex breakdown in the central region. The outer recirculation zone

Section: Resultsmentioning

confidence: 99%

Entropy: An Inspiring Tool for Characterizing Turbulence–Combustion Interaction in Swirling Flames via Direct Numerical Simulations of Non-Premixed and Premixed Flames

Su,

Liu,

Xiao

et al. 2023

Entropy

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“…CH * and OH * show different characteristics in the chemical reaction. These elements are extensively applied when determining chemical zones, identification of heat release, and evaluation of combustion equivalent ratio [23][24][25]. Higgins et al investigated the relations of chemiluminescence of OH * with pressure and equivalent ratio, which expanded the application range of chemiluminescence [26].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Flame Chemiluminescence and Flow Characteristics of a Reverse-Flow Combustor

et al. 2022

International Journal of Aerospace Engineering

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The reverse-flow combustor is extensively applied in small engines due to its compact structure. The cold-state flow characteristics, the ignition process, and flame chemiluminescence characteristics of the reserve-flow combustor were investigated experimentally. Using the particle imaging velocimeter, the cold-state time-averaged flow fields at three different total pressure loss coefficients ζ B are examined. The ignition processes of the combustor, as well as flame characteristics during stable combustion at different equivalent ratios φ , are analyzed based on flame chemiluminescence imaging when ζ B is 3%. As ζ B increases from 1% to 5%, the flow field of the combustor remains almost unchanged while the flow velocity increases. For ζ B =3%, the ignition time T drops from 26 ms to 16 ms with an increase of φ . In addition, the ignition performance is enhanced. Proportions of the T2 phase (quasi-stable phase) are 73%, 68%, and 66%, respectively, suggesting that the quasi-stable phase is the key to successful ignition. As φ increases, the flame becomes thinner and shorter. Furthermore, standard deviations of continuous image areas of CH ∗ and OH ∗ drop from 0.0143 and 0.0132 to 0.0115 and 0.0109, respectively, which indicates the enhancement of combustion stability. According to the brightness distributions of CH ∗ and OH ∗ along the axial direction of the combustor at different equivalent ratios, the production of OH ∗ is significantly affected by the temperature. It can be adopted as an important sign of heat release during combustion.

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Enhancement of Blowout Limits in Lifted Swirled Flames in Methane-Air Combustor by the Use of Sinusoidally Driven Plasma Discharges

Giorgi

Bonuso

Mehdi

et al. 2021

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Effect of the fuel-air flow velocity on heat release rate of swirling non-premixed methane flames

Cited by 23 publications

References 27 publications

Entropy: An Inspiring Tool for Characterizing Turbulence–Combustion Interaction in Swirling Flames via Direct Numerical Simulations of Non-Premixed and Premixed Flames

Entropy: An Inspiring Tool for Characterizing Turbulence–Combustion Interaction in Swirling Flames via Direct Numerical Simulations of Non-Premixed and Premixed Flames

Experimental Investigation on Flame Chemiluminescence and Flow Characteristics of a Reverse-Flow Combustor

Enhancement of Blowout Limits in Lifted Swirled Flames in Methane-Air Combustor by the Use of Sinusoidally Driven Plasma Discharges

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