Large Eddy Simulation of Evaporating Spray with a Stochastic Breakup Model

Irannejad, Abolfazl; Jaberi, Farhad

doi:10.4271/2013-01-1101

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…Furthermore, the droplet relative velocity is reduced by wake interactions of nearby droplets in the spray [70]. This modified relative velocity is then used for droplet motion, heat and mass transfer calculations.…”

Section: Spray Equationsmentioning

confidence: 99%

Large eddy simulation of turbulent spray combustion

Irannejad

Banaeizadeh

Jaberi

2015

Combustion and Flame

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The two-phase filtered mass density function (FMDF) method is employed for large eddy simulation (LES) of high speed evaporating and combusting nheptane sprays using simple (global) and complex (skeletal) chemical kinetic mechanisms. The resolved fluid velocity and pressure fields are obtained by solving the filtered compressible Navier-Stokes equations with high-order Eulerian finite difference methods. The liquid spray and gas scalar (temperature and species mass fractions) fields are both obtained by Lagrangian stochastic models. The chemistry calculation is accelerated by incorporating the parallel in situ adaptive tabulation (ISAT) method. There are two-way interactions among Eulerian and Lagrangian fields. Simulations of evaporating sprays with and without combustion indicate that the two-phase LES/FMDF results are consistent and compare well with the available experimental data at different gas temperatures and oxygen concentrations. The spray controlled flame tends to move away from a diffusion flame structure toward a premixed one as the oxygen concentration decreases and/or the ambient gas temperature increases because of changes in spray-induced turbulence and mixing. The LES/FMDF results for ignition delay show more sensitivity to the chemical kinetic model at lower gas temperatures due to slower reaction and stronger turbulence-chemistry interactions. The liftoff length is less sensitive to the kinetics.

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Section: Spray Equationsmentioning

confidence: 99%

Large eddy simulation of turbulent spray combustion

Irannejad

Banaeizadeh

Jaberi

2015

Combustion and Flame

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“…In two-phase flows, Lagrangian stochastic models can be used to analyze additional effects such as thermophoresis, electrophoresis or chemical forces [24][25][26] (due to interface chemistry in liquid medium). Other typical examples include droplets or coal/fuel particles where models are added to simulate complex combustion or evaporation processes [7,8,27,28]. Yet, these practical developments can be ruined by a poor formulation of the model retained for the velocity of fluid particles or the velocity of the fluid seen.…”

Section: Introductionmentioning

confidence: 99%

Guidelines for the formulation of Lagrangian stochastic models for particle simulations of single-phase and dispersed two-phase turbulent flows

Minier¹,

Chibbaro

Pope

2014

Physics of Fluids

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In this paper, we establish a set of criteria which are applied to discuss various formulations under which Lagrangian stochastic models can be found. These models are used for the simulation of fluid particles in single-phase turbulence as well as for the fluid seen by discrete particles in dispersed turbulent two-phase flows. The purpose of the present work is to provide guidelines, useful for experts and non-experts alike, which are shown to be helpful to clarify issues related to the form of Lagrangian stochastic models. A central issue is to put forward reliable requirements which must be met by Lagrangian stochastic models and a new element brought by the present analysis is to address the single-and two-phase flow situations from a unified point of view. For that purpose, we consider first the single-phase flow case and check whether models are fully consistent with the structure of the Reynolds-stress models. In the two-phase flow situation, coming up with clear-cut criteria is more difficult and the present choice is to require that the single-phase situation be well-retrieved in the fluidlimit case, elementary predictive abilities be respected and that some simple statistical features of homogeneous fluid turbulence be correctly reproduced. This analysis does not address the question of the relative predictive capacities of different models but concentrates on their formulation since advantages and disadvantages of different formulations are not always clear. Indeed, hidden in the changes from one structure to another are some possible pitfalls which can lead to flaws in the construction of practical models and to physically unsound numerical calculations. A first interest of the present approach is illustrated by considering some models proposed in the literature and by showing that these criteria help to assess whether these Lagrangian stochastic models can be regarded as acceptable descriptions. A second interest is to indicate how future developments can be safely built, which is also relevant for stochastic subgrid models for particle-laden flows in the context of Large Eddy Simulations. C 2014 AIP Publishing LLC. [http://dx.

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Numerical study of high speed evaporating sprays

Irannejad

Jaberi

2015

International Journal of Multiphase Flow

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Large eddy simulations of high speed evaporating sprays are conducted to study spray interactions with the gas flow and turbulence generated by the spray. The spray is simulated with a Lagrangian droplet method and a stochastic breakup model together with non-equilibrium, finite-rate heat and mass transfer models. The Lagrangian spray/droplet field is fully coupled with the Eulerian gas flow through mass, momentum and energy coupling terms. The interaction of spray induced gas flow and turbulence with the droplets is studied for different gas chamber densities and temperatures as well as different nozzle sizes and injection pressures. Our results indicate that although the droplet transport and evaporation are both important to the generated gas flow and its interactions with the spray, the major source of momentum transfer to the gas is the high speed vapor generated by evaporation. It is shown that sprays injected from larger nozzles generate more perturbations in the gas due to increase in evaporation rate by higher entrained gas. However, the liquid spray penetration remains unchanged with the variation in injection pressure due to competing effects of evaporation and vapor convection. While the liquid penetration is not significantly affected by the injection pressure, the evaporated vapor penetrates more and mixes better at higher injection pressures due to higher induced gas velocity and turbulence.

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Large Eddy Simulation of Evaporating Spray with a Stochastic Breakup Model

Cited by 3 publications

References 23 publications

Large eddy simulation of turbulent spray combustion

Large eddy simulation of turbulent spray combustion

Guidelines for the formulation of Lagrangian stochastic models for particle simulations of single-phase and dispersed two-phase turbulent flows

Numerical study of high speed evaporating sprays

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