On the formation and early evolution of soot in turbulent nonpremixed flames

Bisetti, Fabrizio; Blanquart, Guillaume; Müeller, Michael E.; Pitsch, Heinz

doi:10.1016/j.combustflame.2011.05.021

Cited by 199 publications

(152 citation statements)

References 53 publications

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“…Instead, we suspect that the turbulent and molecular transport mechanisms which are responsible for the movement of recently nucleated droplets from the cold side of the mixing lower towards the warm side are less well developed or not as accurately represented in the current LES-PBE-PDF model. The molecular transport is accounted for by the micromixing model and influenced, to a large extend, by differential diffusion between droplets and fluid phase species [8,73]. Although our micromixing model encompasses a contribution due to differential fluid-droplet diffusion, both the fluid and droplet phases mix according to the same micromixing rate at present.…”

Section: Droplet Condensation In a Turbulent Mixing Layermentioning

confidence: 99%

An LES-PBE-PDF approach for modeling particle formation in turbulent reacting flows

Sewerin

Rigopoulos

2017

Physics of Fluids

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Many chemical and environmental processes involve the formation of a polydispersed particulate phase in a turbulent carrier flow. Frequently, the immersed particles are characterized by an intrinsic property such as the particle size and the distribution of this property across a sample population is taken as an indicator for the quality of the particulate product or its environmental impact.In the present article, we propose a comprehensive model and an efficient numerical solution scheme for predicting the evolution of the property distribution associated with a polydispersed particulate phase forming in a turbulent reacting flow. Here, the particulate phase is described in terms of the particle number density whose evolution in both physical and particle property space is governed by the population balance equation (PBE). Based on the concept of large eddy simulation (LES), we augment the existing LES-transported PDF approach for fluid phase scalars by the particle number density and obtain a modelled evolution equation for the filtered probability density function (PDF) associated with the instantaneous fluid composition and particle property distribution. This LES-PBE-PDF approach allows us to predict the LES-filtered fluid composition and particle property distribution at each spatial location and point in time without any restriction on the chemical or particle formation kinetics. In view of a numerical solution, we apply the method of Eulerian stochastic fields, invoking an explicit adaptive grid technique in order to discretize the stochastic field equation for the number density in particle property space. In this way, sharp moving features of the particle property distribution can be accurately resolved at a significantly reduced computational cost.As a test case, we consider the condensation of an aerosol in a developed turbulent mixing layer. Our investigation not only demonstrates the predictive capabilities of the LES-PBE-PDF model, but also indicates the computational efficiency of the numerical solution scheme.

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Section: Droplet Condensation In a Turbulent Mixing Layermentioning

confidence: 99%

An LES-PBE-PDF approach for modeling particle formation in turbulent reacting flows

Sewerin

Rigopoulos

2017

Physics of Fluids

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“…11,30 Constant non-unity Lewis numbers were employed, 31 and the species Lewis numbers are the same as those listed in the work of Savard and Blanquart. 12 The chemical and transport models were compared against experimental data and numerical results using full transport (mixture-averaged formulation).…”

Section: B Governing Equationsmentioning

confidence: 99%

Vorticity isotropy in high Karlovitz number premixed flames

Bobbitt

Blanquart

2016

Physics of Fluids

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The isotropy of the smallest turbulent scales is investigated in premixed turbulent combustion by analyzing the vorticity vector in a series of high Karlovitz number premixed flame direct numerical simulations. It is found that increasing the Karlovitz number and the ratio of the integral length scale to the flame thickness both reduce the level of anisotropy. By analyzing the vorticity transport equation, it is determined that the vortex stretching term is primarily responsible for the development of any anisotropy. The local dynamics of the vortex stretching term and vorticity resemble that of homogeneous isotropic turbulence to a greater extent at higher Karlovitz numbers. This results in small scale isotropy at sufficiently high Karlovitz numbers and supports a fundamental similarity of the behavior of the smallest turbulent scales throughout the flame and in homogeneous isotropic turbulence. At lower Karlovitz numbers, the vortex stretching term and the vorticity alignment in the strain-rate tensor eigenframe are altered by the flame. The integral length scale has minimal impact on these local dynamics but promotes the effects of the flame to be equal in all directions. The resulting isotropy in vorticity does not reflect a fundamental similarity between the smallest turbulent scales in the flame and in homogeneous isotropic turbulence. Published by AIP Publishing. [http://dx

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“…While significant progress has been made in both chemical kinetics and fluid-chemistry interactions, there is still a need to extend existing simulations of sooting behavior to describe the interplay between soot chemistry and the highly unsteady turbulent flow field seen in practical engine conditions [8,9]. Doing so requires the improvement and validation of numerical models utilizing highquality experimental databases.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Shaddix et al found that soot production increased fourfold for a flickering methane/air flame as compared with a steady flame at the same mean fuel flow velocity [10]. Temporally and spatially resolved data are needed that can contribute to the validation of direct numerical simulation studies, which capture the effects of local curvature, strain, and the duration of interaction between flow structures and flames on soot formation and evolution in turbulent nonpremixed flames [8,11].…”

Section: Introductionmentioning

confidence: 99%

Effects of repetitive pulsing on multi-kHz planar laser-induced incandescence imaging in laminar and turbulent flames

et al. 2015

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Planar laser-induced incandescence (LII) imaging is reported at repetition rates up to 100 kHz using a burstmode laser system to enable studies of soot formation dynamics in highly turbulent flames. To quantify the accuracy and uncertainty of relative soot volume fraction measurements, the temporal evolution of the LII field in laminar and turbulent flames is examined at various laser operating conditions. Under high-speed repetitive probing, it is found that LII signals are sensitive to changes in soot physical characteristics when operating at high laser fluences within the soot vaporization regime. For these laser conditions, strong planar LII signals are observed at measurement rates up to 100 kHz but are primarily useful for qualitative tracking of soot structure dynamics. However, LII signals collected at lower fluences allow sequential planar measurements of the relative soot volume fraction with a sufficient signal-to-noise ratio at repetition rates of 10-50 kHz. Guidelines for identifying and avoiding the onset of repetitive probe effects in the LII signals are discussed, along with other potential sources of measurement error and uncertainty. RightsThis paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: https://www.osapublishing.org/ ol/abstract.cfm?uri=ol-40-9-2029&origin=search. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. Planar laser-induced incandescence (LII) imaging is reported at repetition rates up to 100 kHz using a burst-mode laser system to enable studies of soot formation dynamics in highly turbulent flames. To quantify the accuracy and uncertainty of relative soot volume fraction measurements, the temporal evolution of the LII field in laminar and turbulent flames is examined at various laser operating conditions. Under high-speed repetitive probing, it is found that LII signals are sensitive to changes in soot physical characteristics when operating at high laser fluences within the soot vaporization regime. For these laser conditions, strong planar LII signals are observed at measurement rates up to 100 kHz but are primarily useful for qualitative tracking of soot structure dynamics. However, LII signals collected at lower fluences allow sequential planar measurements of the relative soot volume fraction with a sufficient signal-to-noise ratio at repetition rates of 10-50 kHz. Guidelines for identifying and avoiding the onset of repetitive probe effects in the LII signals are discussed, along with other potential sources of measurement error and uncertainty.

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On the formation and early evolution of soot in turbulent nonpremixed flames

Cited by 199 publications

References 53 publications

An LES-PBE-PDF approach for modeling particle formation in turbulent reacting flows

An LES-PBE-PDF approach for modeling particle formation in turbulent reacting flows

Vorticity isotropy in high Karlovitz number premixed flames

Effects of repetitive pulsing on multi-kHz planar laser-induced incandescence imaging in laminar and turbulent flames

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