A simple spray–flamelet model: Influence of ambient temperature and fuel concentration, vaporisation source and fuel injection position

Maionchi, Daniela; Fachini, Fernando F.

doi:10.1080/13647830.2013.781225

Cited by 5 publications

(7 citation statements)

References 31 publications

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“…The model for the vaporisation of droplets is modified from [19] to account for the gas-liquid relative motion. The source term can then be written as…”

Section: Resultsmentioning

confidence: 99%

“…The governing equations are formulated in an Eulerian framework, assuming steady-state and the low-Mach number limit for the gas phase [19,20]. For simplicity, infinitely fast chemistry is considered (Burke-Schumann limit), enabling the diffusion flame to be described in terms of the extended Shvab-Zel'dovich model [21].…”

Section: Physical Modelmentioning

confidence: 99%

“…Governing equations in physical space -x 2.1.1. Gaseous Phase The gaseous phase is described in x = {x 1 , x 2 , x 3 } -space by the following dimensionless conservation equations of mass, momentum, fuel/oxidant mass fractions, and energy [19],…”

Section: Physical Modelmentioning

confidence: 99%

“…The droplet radius and evaporation rate spatial distributions are presented in Fig. 5, as in [19]. The droplet radius is initially constant, and decreases as it approaches the flame until the droplet is fully vaporised (see Fig.…”

Section: Unity Le and Zero Stmentioning

confidence: 99%

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A generalised spray-flamelet formulation by means of a monotonic variable

Maionchi

Santos

Melguizo-Gavilanes

et al. 2021

Combustion Theory and Modelling

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The external structure of the spray-flamelet can be described using the Schvab-Zel'dovich-Liñan formulation. The gaseous mixture-fraction variable as function of the physical space, Z(x i ), typically employed for the description of gaseous diffusion flames leads to non-monotonicity behaviour for spray flames due to the extra fuel supplied by vaporisation of droplets distributed into the flow. As a result, the overall properties of spray flames depend not only on Z and the scalar dissipation rate, χ, but also on the spray source term, S v . We propose a new general coordinate variable which takes into account the spatial information about the entire mixture fraction due to the gaseous phase and droplet vaporisation. This coordinate variable, Z C (x i ) is based on the cumulative value of the gaseous mixture fraction Z(x i ), and is shown to be monotonic. For pure gaseous flow, the new cumulative function, Z C , yields the well-established flamelet structure in Z-space. In the present manuscript, the spray-flamelet structure and the new equations for temperature and mass fractions in terms of Z C are derived and then applied to the canonical counterflow configuration with potential flow. Numerical results are obtained for ethanol and methanol sprays, and the effect of Lewis and Stokes numbers on the spray-flamelet structure are analyzed. The proposed formulation agrees well when mapping the structure back to physical space thereby confirming our integration methodology.

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“…The model for the vaporisation of droplets is modified from [19] to account for the gas-liquid relative motion. The source term can then be written as…”

Section: Resultsmentioning

confidence: 99%

Section: Physical Modelmentioning

confidence: 99%

Section: Physical Modelmentioning

confidence: 99%

Section: Unity Le and Zero Stmentioning

confidence: 99%

See 2 more Smart Citations

A generalised spray-flamelet formulation by means of a monotonic variable

Maionchi

Santos

Melguizo-Gavilanes

et al. 2021

Combustion Theory and Modelling

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“…Luo et al [32] extended the classical mixture fraction flamelet transformation to spray flames, but only for pre-vaporized conditions that serve the definition of the boundary conditions for the gaseous flamelet equations. Olguin and Gutheil [27,33], Greenberg et al [11,[18][19][20] and Maionchi and Fachini [34] directly solved the spray flame equations in physical space and subsequently represented the flame structure in the Z g -space; for example by separating the purely gaseous region of the flame from the evaporation zone [27,33]. However, due to the non-monotonicity, the classical gaseous definition cannot be used to solve the spray flamelet equations in composition space.…”

Section: Introductionmentioning

confidence: 99%

On the generalisation of the mixture fraction to a monotonic mixing-describing variable for the flamelet formulation of spray flames

Franzelli

Vié

Ihme

2015

Combustion Theory and Modelling

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International audienceSpray flames are complex combustion configurations that require the consideration of competing processes between evaporation, mixing and chemical reactions. The classical mixture- fraction formulation, commonly employed for the representation of gaseous diffusion flames, cannot be used for spray flames due to its non-monotonicity. This is a consequence of the presence of an evaporation source term in the corresponding conservation equation. By addressing this issue, a new mixing-describing variable, called effective composition variable η, is defined to enable the general analysis of spray-flame structures in composition space. This quantity combines the gaseous mixture fraction Zg and the liquid-to-gas mass ratio Z. This new expression reduces to the classical mixture-fraction definition for gaseous systems, thereby ensuring consistency. The versatility of this new expression is demonstrated in application to the analysis of counterflow spray flames. Following this analysis, the effective composition variable η is employed for the derivation of a spray-flamelet formulation. The consistent representation in both effective-composition space and physical space is guaranteed by construction and the feasibility of solving the resulting spray-flamelet equation in this newly defined composition space is demonstrated numerically. A model for the scalar dissipation rate is proposed to close the derived spray-flamelet equations.The laminar one-dimensional counterflow spray flamelet equations are numerically solved in the η-space and compared to the physical-space solutions. It is shown that the hysteresis and bifurcation characterizing the flame structure response to variations of droplet diameter and strain rate are correctly reproduced by the proposed composition-space formulation

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