Modeling of Fine-Particle Formation in Turbulent Flames

Abstract

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

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

“…Soot generation is intricately linked to gas-phase thermochemical conditions as well as the trajectories of the soot particles in the combustor [2,3] . Due to this inherent complexity, predictions of soot inside aircraft engines has been a formidable challenge.…”

“…Due to this inherent complexity, predictions of soot inside aircraft engines has been a formidable challenge. In particular, a host of models for describing the turbulent flow, the gas-phase combustion, and soot generation and evolution as well as the interactions of these processes are needed [2,[4][5][6][7] . While there has been considerable progress in the modeling of soot formation processes [8,9] , the application of these advances to realistic combustor configurations still remain sparse.…”

Large-eddy simulation of turbulent dispersed flows: a review of modelling approaches

“…Modelling capabilities are much less established in flows where these processes occur at the smallest scales (e.g. molecular mixing and chemical reactions in turbulent combustion at high Reynolds and Damkohler numbers [67,88,95,96,103,104], droplet break-up in liquid spray atomization at high Weber number [7,15] or momentum transfer in near-wall flows at high Reynolds number [58,96]). …”

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

“…This leads to the method of moments which was introduced by Hulburt and Katz [25] and has, until now, been one of the most popular approaches for characterizing particulate phases in spatially inhomogeneous flows. Frequently, low order moments are important from an engineering perspective, for example, the total particle number density or volume fraction [60], or directly accessible by measurement techniques [18]. On the minus side, the moment transport equations are only closed for certain functional forms of the particle growth, coagulation and breakage rates [7,14] and, in general, require an assumption on the shape of the particle property distribution to be closed.…”

“…Only in passing we mention the formulation of other moment-based methods such as the method of moments with interpolative closure (MOMIC) [17] and the hybrid method of moments (HMOM) [44], also see Rigopoulos [62] and Marchisio and Fox [41]. Following Raman and Fox [60], moment-based methods are computationally very economical, in particular, if the particle property space comprises more than one dimension.…”