Influence of evaporation on spray flamelet structures

Olguin, Hernan; Gutheil, Eva

doi:10.1016/j.combustflame.2013.10.010

Cited by 69 publications

(51 citation statements)

References 33 publications

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“…Robinson, 1956). As shown by Gutheil and Sirignano (1998), this can be successfully handled in the self-similar counterflow formulation by consideration of different "sheets of solutions," thereby enabling computations that may account for oscillatory droplet trajectories (Gutheil, 2001;Hollmann and Gutheil, 1998;Olguin and Gutheil, 2014). The multicontinua formulation can be extended to the treatment of realistic droplet-size distributions by consideration of a large number of droplet classes (or "sectionals").…”

Section: Introductionmentioning

confidence: 99%

Regimes of Spray Vaporization and Combustion in Counterflow Configurations

Liñán

Martínez-Ruiz

Sánchez

et al. 2014

Combustion Science and Technology

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Section: Introductionmentioning

confidence: 99%

Regimes of Spray Vaporization and Combustion in Counterflow Configurations

Liñán

Martínez-Ruiz

Sánchez

et al. 2014

Combustion Science and Technology

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“…Many different approaches have been proposed to take into account the enthalpy loss effect of droplet evaporation. For example, spray flamelets [26], using total enthalpy as progress variable [3], partially premixed flamelet method [19] or generating FGM table by solving new spray flamelets equations as derived in [31] and [43]. In this study, as a first step of the model validation, an adiabatic gaseous FGM table generated by using pure fuel vapor as fuel stream is employed, and enthalpy loss is not included in this 2D FGM table.…”

Section: Combustion Modelmentioning

confidence: 99%

“…However, the high dimensionality of the spray flamelets makes them difficult to tabulate and use. A novel two dimensional spray flamelet, using mixture fraction and droplet evaporation rate as independent variables, was recently proposed by Olguin and Gutheil [43]. However, the shape of the PDF for droplet evaporation rate is still an open issue for the application of this model with presumed PDF methods.…”

Section: Introductionmentioning

confidence: 99%

Transported PDF Modeling of Ethanol Spray in Hot-Diluted Coflow Flame

Naud

Roekaerts

2015

Flow Turbulence Combust

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This paper presents a numerical modeling study of one ethanol spray flame from the Delft Spray-in-Hot-Coflow (DSHC) database, which has been used to study Moderate or Intense Low-oxygen Dilution (MILD) combustion of liquid fuels (Correia Rodrigues et al. Combust. Flame 162, 759-773, 2015). A "Lagrangian-Lagrangian" approach is adopted where both the joint velocity-scalar Probability Density Function (PDF) for the continuous phase and the joint PDF of droplet properties are modeled and solved. The evolution of the gas phase composition is described by a Flamelet Generated Manifold (FGM) and the interaction by exchange with the mean (IEM) micro-mixing model. Effects of finite conductivity on droplet heating and evaporation are accounted for. The inlet boundary conditions starting in the dilute spray region are obtained from the available experimental data together with the results of a calculation of the spray including the dense region using ANSYS Fluent 15. A method is developed to determine a good estimation for the initial droplet temperature. The inclusion of the "1/3" rule for droplet evaporation and dispersion models is shown to be very important. The current modeling approach is capable of accurately predicting main properties, including mean velocity, droplet mean diameter and number density. The gas temperature is under-predicted in the region where the enthalpy loss due to droplet evaporation is important. The flame structure analysis reveals the existence of two heat release regions, respectively having the characteristics of a premixed and a diffusion flame. The experimental and modeled temperature PDFs are compared, highlighting the capabilities and limitations of the proposed model.

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“…For this purpose, a set of spray flamelet equations in terms of mixture fraction and a reaction progress variable is derived, which is suitable to include all combustion regimes appearing in spray flames. These equations comprise the two-dimensional gas flamelet equations of Knudsen and Pitsch [14,15] if no spray is present, and they reduce to the spray flamelet equations of Olguin and Gutheil [8] if premixed effects may be neglected. Moreover, the negligence of premixed regimes in Hollmann and Gutheil's [1] study will be investigated.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Olguin and Gutheil [8] derived a set of non-premixed spray flamelet equations, which are formulated in mixture fraction space, which is the procedure typically followed in gas combustion [9]. The new spray flamelet equations [8] also take evaporation effects into account, and they reduce to the classical gas non-premixed flamelet equations if evaporation does not occur.…”

Section: Introductionmentioning

confidence: 99%

Derivation and Evaluation of a Multi-regime Spray Flamelet Model

Olguin¹,

Gutheil

2014

Zeitschrift Für Physikalische Chemie

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Abstract:The formulation of a comprehensive flamelet model to consider detailed chemical reaction mechanisms in the simulation of turbulent spray flames is a very challenging task due to the inherent multi-regime structure of spray flames. Non-premixed, premixed, and evaporation-controlled combustion regimes may be found in a single spray flame. Recently, attempts have been made to extend classical single regime flamelet models to more complex situations, where at least two combustion regimes coexist. The objective of this work is to develop a framework in which two-regime flamelet models can be described and combined in order to advance the development of a comprehensive flamelet model for turbulent spray flames. For this purpose, a set of spray flamelet equations in terms of the mixture fraction and a reaction progress variable is derived, which includes the evaporation, characterizing the spray flames, and which describes all combustion regimes appearing in spray flames. The two-regime and single regime flamelet equations available in the literature are retrieved from these multi-dimensional spray flamelet equations as special cases. The derived set of spray flamelet equations is then used to evaluate structures of laminar ethanol/air spray flames in the counterflow configuration in order to determine the significance of different combustion regimes. The present study concerns spray flames with no pre-vaporized liquid in the oxidizing gas phase, and it is found that only non-premixed and evaporation-controlled combustion regimes exist, so that premixed effects may be neglected. Moreover, an exact transport equation for the scalar dissipation rate is derived, which explicitly takes spray evaporation and detailed transport into account. This equation is then used to evaluate assumptions commonly adopted in the literature. The results show that the spatial variation of the mean molecular weight of the mixture may be neglected in the formulation of the mixture fraction, but it may be significant for its scalar dissipation rate. The assumption of unity Lewis number may lead to non-physical values of the scalar dissipation rate of the mixture fraction, whereas the use of a mass-averaged diffusion coefficient of the mixture is a good approximation for the spray flames under investigation.

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Influence of evaporation on spray flamelet structures

Cited by 69 publications

References 33 publications

Regimes of Spray Vaporization and Combustion in Counterflow Configurations

Regimes of Spray Vaporization and Combustion in Counterflow Configurations

Transported PDF Modeling of Ethanol Spray in Hot-Diluted Coflow Flame

Derivation and Evaluation of a Multi-regime Spray Flamelet Model

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