Nonpremixed and premixed flamelets LES of partially premixed spray flames using a two-phase transport equation of progress variable

Hu, Yong; Kurose, Ryoichi

doi:10.1016/j.combustflame.2017.10.004

Cited by 47 publications

(23 citation statements)

References 55 publications

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“…The ratios a d /η k as well as a d /∆x remain comparable to several previous analyses by other authors 5,31,[39][40][41][42][43][44] , and thus the assumption of sub-grid point sources (similar to Refs. [30][31][32][39][40][41][42][43][44][45][46][47][48][49] ) is not expected to significantly affect the ignition phenomenon and subsequent flame-droplet interaction. The Stokes number, defined as…”

Section: Numerical Implementationmentioning

confidence: 99%

Edge flame propagation statistics in igniting monodisperse droplet-laden mixtures

et al. 2019

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The effects of droplet diameter, overall (i.e., liquid+gaseous phases) equivalence ratio, and turbulence intensity on the edge flame propagation statistics for localized forced ignition of uniformly dispersed n-heptane droplet-laden mixtures under homogeneous isotropic decaying turbulence have been analyzed based on direct numerical simulations data. It has been found that the edge flame structure becomes increasingly prominent for large overall equivalence ratios and droplet diameters. Although the mean edge flame speed has been found to be positive and its most probable value remains comparable to the theoretical value for laminar edge flames in purely gaseous mixtures, the mean values have been found to decrease and the probabilities of finding locally negative edge flame speeds have been found to increase with increasing turbulence intensity. The marginal probability density function and curvature and strain rate dependences of the edge flame speed have been found to be principally governed by the displacement speed of the fuel mass fraction isosurface intersecting the stoichiometric mixture fraction isosurface. The displacement speed of the stoichiometric mixture fraction isosurface has also been found to influence the local scalar gradient dependences of the edge flame speed in this configuration, especially for large droplets. The displacement speed of the fuel mass fraction isosurface Sd has been found to be principally governed by leading order contributions of the reaction and molecular diffusion components and the evaporation contribution remains weak in comparison to these leading order contributors. The local edge flame speed exhibits nonlinear curvature and strain rate dependences and its variation with the magnitudes of both fuel mass fraction and mixture fraction gradients has been found to be nonmonotonic for all cases considered here. The correlations of the edge flame speed with curvature, strain rate, and scalar gradient have been found to be qualitatively similar to the corresponding statistics reported in the existing literature for edge flames in purely gaseous mixtures. Additionally, the curvature and tangential strain rate dependences of the edge flame speed have been found to be dependent on the droplet size and overall equivalence ratio, and these dependences become weak for cases with large droplets.

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Section: Numerical Implementationmentioning

confidence: 99%

Edge flame propagation statistics in igniting monodisperse droplet-laden mixtures

et al. 2019

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“…Numerical simulations are performed by using an in-house thermal flow analysis code called FK 3 (e.g. Kitano et al, 2015;Hu and Kurose, 2018;Hu and Kurose, 2019;Pillai and Kurose, 2019;Ahmed et al, 2019;Pillai et al, 2020). This code is pressure-based semi-implicit solver for compressible flows and the fractional-step method based on characteristic splitting is employed (Moureau et al, 2007).…”

Section: Numerical Proceduresmentioning

confidence: 99%

Numerical investigations of C1-C3 alkanes and H<sub>2</sub> premixed flame-wall interaction: Effectiveness of insulation wall on heat loss reduction

Kai

Takahashi

Kurose

2020

JTST

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Conjugate heat transfer analyses of premixed flames propagating toward the insulation or Al alloy wall are performed for C1 to C3 alkanes and H 2 flames at different equivalence ratios of ϕ = 0.6, 0.8, 1.0 and 1.2 under a high pressure condition of 2 MPa in terms of one-dimensional numerical simulations with detailed reaction mechanisms (70 species and 321 reactions for alkanes, 9 species and 19 reactions for H 2 ). The effects of the equivalence ratio and fuel properties on the heat loss reduction through the wall due to the insulation are investigated in detail. The results show that for all the alkanes and H 2 flames, the temperature at the surface of the insulation wall increases more and faster than that of the Al alloy wall, and the heat loss is reduced due to the insulation. Furthermore, the heat loss reduction rate Λ for the insulation wall to the Al alloy wall becomes higher both with the increase and decrease in the equivalence ratio from the stoichiometric ratio, regardless of the fuel. The value of Λ reaches up to 2.1%. The reason for this tendency of Λ against the equivalence ratio can be explicitly explained by the time variations of gas thermal conductivity and gas temperature gradient in the vicinity of the wall, which control the heat flux through the wall.

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“…Further details of the numerical set-up can be found in [13]. The simulation has been performed using the code known as FK 3 [13,[16][17][18]. The coupling between Eulerian and Lagrangian phases is achieved via the Particle-Source-In-Cell approach [13].…”

Section: Dns Datamentioning

confidence: 99%

Statistics of reaction progress variable and mixture fraction gradients of a pulverised coal jet flame using Direct Numerical Simulation data

Ahmed

d’Auzay

Muto

et al. 2019

Proceedings of the Combustion Institute

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The statistical behaviour of the variances, covariance and gradients of the reaction progress variable (c), and the mixture fraction (ξ) have been analysed in a pulverised coal jet flame using a three-dimensional carrier phase direct numerical simulation (DNS) dataset. It has been observed that the Favre-PDFs of c and ξ can be parametrised by the standard β function. Furthermore, the log-normal distribution has been found to accurately represent |∇c| and |∇ξ|. It is also found that ∇c and ∇ξ remain aligned throughout the flame brush. Finally the joint PDF of |∇c| and |∇ξ| has been compared with the product of the PDF of |∇c| and PDF of |∇ξ| extracted from carrier phase DNS, and it has been found that |∇c| and |∇ξ| are not statistically independent in the case investigated.The bivariate log-normal distributions with and without correlation have also been considered, and the former is

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Nonpremixed and premixed flamelets LES of partially premixed spray flames using a two-phase transport equation of progress variable

Cited by 47 publications

References 55 publications

Edge flame propagation statistics in igniting monodisperse droplet-laden mixtures

Edge flame propagation statistics in igniting monodisperse droplet-laden mixtures

Numerical investigations of C1-C3 alkanes and H<sub>2</sub> premixed flame-wall interaction: Effectiveness of insulation wall on heat loss reduction

Statistics of reaction progress variable and mixture fraction gradients of a pulverised coal jet flame using Direct Numerical Simulation data

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