Large‐eddy simulation modeling of turbulent flame synthesis of titania nanoparticles using a bivariate particle description

Sung, Yonduck; Raman, Venkat; Koo, Heeseok; Mehta, Manik; Fox, Rodney O.

doi:10.1002/aic.14279

Cited by 21 publications

(14 citation statements)

References 37 publications

(119 reference statements)

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“…The evolution of a population of fine, that is non-inertial, particles in a carrier fluid can be described by a population balance equation (PBE) [1,2,3,4,5,6,7,8,9,10]. There are many potential applications such as soot modeling, aerosol technology, nanoparticle synthesis, microbubbles, reactive precipitation, and coal combustion (see [5] and references therein).…”

Section: Introductionmentioning

confidence: 99%

Strongly coupled fluid-particle flows in vertical channels. II. Turbulence modeling

2016

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In Part I, simulations of strongly coupled fluid-particle flow in a vertical channel were performed with the purpose of understanding, in general, the fundamental physics of wall-bounded multiphase turbulence and, in particular, the roles of the spatially correlated and uncorrelated components of the particle velocity.The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions were presented, and the unclosed terms that are retained in the context of fully developed channel flow were evaluated in an Eulerian-Lagrangian (EL) framework. Here, data from the EL simulations are used to validate a multiphase Reynolds-stress model (RSM) that predicts the wall-normal distribution of the two-phase, one-point turbulence statistics up to second order. It is shown that the anisotropy of the Reynolds stresses both near the wall and far away is a crucial component for predicting the distribution of the RA particle-phase volume fraction. Moreover, the decomposition of the phase-average (PA) particle-phase fluctuating energy into the spatially correlated and uncorrelated components is necessary to account for the boundary conditions at the wall. When these factors are properly accounted for in the RSM, the agreement with the EL turbulence statistics is satisfactory at first order (e.g., PA velocities) but less so at second order (e.g., PA turbulent kinetic energy). Finally, an algebraic stress model for the PA particle-phase pressure tensor and the Reynolds stresses is derived from the RSM using the weak-equilibrium assumption.

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Section: Introductionmentioning

confidence: 99%

Strongly coupled fluid-particle flows in vertical channels. II. Turbulence modeling

2016

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“…In the CQMOM approach [40,41] , the marginal NDF of volume is discretized using two delta functions, while the conditional NDF of surface area conditioned on volume coordinate is discretized using a single delta function. The moments of the NDF are then written as [40] :…”

Section: Soot Statistical Descriptionmentioning

confidence: 99%

Effect of soot model, moment method, and chemical kinetics on soot formation in a model aircraft combustor

Chong

Raman

Müeller

et al. 2019

Proceedings of the Combustion Institute

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CitationChong ST, Raman V, Mueller ME, Selvaraj P, Im HG (2018 AbstractThe simulation of turbulent sooting flames requires a host of models, of which the two critical components are the chemical kinetics that describe soot precursor evolution and the description of the soot population. The purpose of this study is to understand the sensitivity of soot predictions in a realistic aircraft combustor to model choices for these components. Two different chemistry mechanisms, three different statistical approaches, and two different soot inception models are considered. The simulations show that acetylene-based soot inception produces very high soot volume fraction, with the soot particles present predominantly in the inner recirculation zone of the swirl-stabilized combustor. The PAH-based nucleation models lead to soot generation in the shear layers emanating from fuel injection. The two advanced statistical approaches (Hybrid and Conditional Quadrature Method of Moments) also show significant differences. While the Hybrid method produces lower soot number density, it also generates larger soot particles due to a faster predicted rate of coagulation. The Conditional Quadrature approach produces much higher soot number density, but its particle sizes are smaller compared to the Hybrid method for all kinetic mechanisms considered. This experimental combustor is strongly dominated by surface growth based soot mass addition. As a result, even if nucleation/condensation rates are different, the final soot mass yield is comparable for PAH-based soot models. These results indicate the importance of not only the chemical mechanism, which may be less important in this surface growth dominated combustor, but also the soot statistical model, to which coagulation and the soot surface area are relatively sensitive.

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“…Consistent with the engineering approach to nanoparticle synthesis, the use of LES and other detailed flow models has emerged only recently (see, e.g., Loeffler et al 2011;Sung et al 2011Sung et al , 2013. Figure 6 shows LES of titania synthesis from a titanium tetrachloride precursor in a methane-air flame.…”

Section: Large-eddy Simulationsmentioning

confidence: 97%

Modeling of Fine-Particle Formation in Turbulent Flames

Raman

Fox

2016

Annu. Rev. Fluid Mech.

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The generation of nanostructured particles in high-temperature flames is important both for the control of emissions from combustion devices and for the synthesis of high-value chemicals for a variety of applications. The physiochemical processes that lead to the production of fine particles in turbulent flames are highly sensitive to the flow physics and, in particular, the history of thermochemical compositions and turbulent features they encounter. Consequently, it is possible to change the characteristic size, structure, composition, and yield of the fine particles by altering the flow configuration. This review describes the complex multiscale interactions among turbulent fluid flow, gas-phase chemical reactions, and solid-phase particle evolution. The focus is on modeling the generation of soot particles, an unwanted pollutant from automobile and aircraft engines, as well as metal oxides, a class of high-value chemicals sought for specialized applications, including emissions control. Issues arising due to the numerical methods used to approximate the particle number density function, the modeling of turbulence-chemistry interactions, and model validation are also discussed. 159

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Large‐eddy simulation modeling of turbulent flame synthesis of titania nanoparticles using a bivariate particle description

Cited by 21 publications

References 37 publications

Strongly coupled fluid-particle flows in vertical channels. II. Turbulence modeling

Strongly coupled fluid-particle flows in vertical channels. II. Turbulence modeling

Effect of soot model, moment method, and chemical kinetics on soot formation in a model aircraft combustor

Modeling of Fine-Particle Formation in Turbulent Flames

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