Application of an unsteady flamelet model in a RANS framework for spray A simulation

Desantes, J.M.; García-Oliver, José M; Novella, Ricardo; Pérez-Sánchez, Eduardo J.

doi:10.1016/j.applthermaleng.2017.01.101

Cited by 29 publications

(29 citation statements)

References 44 publications

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“…The injection rate lasts for more than 4 ms in order to describe the quasi-steady fields. More details about the injection rate can be found in [6,20]. …”

Section: Parametric Studymentioning

confidence: 99%

“…Consequently, the ADF model establishes two hypotheses, namely, to solve only the flamelet equation for the progress variable and to decouple the chemical source term of the diffusion processes. Although, at first glance, it may seem very restrictive constrains this model has been successfully applied to diesel-like sprays [6], diesel engines and furnaces [5,14,15]. For this work, the progress variable is defined as Yc = YCO + YCO 2 [4].…”

Section: Model Descriptionmentioning

confidence: 99%

“…The liquid phase is modeled with a DDM (discrete droplet method) based on the Kelvin-Helmholtz and Rayleigh-Taylor instabilities for describing the atomization and breakup processes in conjunction with the Ranz-Marshall model for droplet evaporation. A detailed description of the model constants used for these simulations can be found in a previous work of the authors [6]. The combustion model is based on the flamelet concept which describes the turbulent combustion as an ensemble of laminar flames, called flamelets, embedded in the turbulent flame.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Cylindrical symmetry is supposed and, consequently, calculation is performed on a meridian cut, with dimensions 54 × 108 mm. The mesh is structured with constant cell size of 0.25 × 0.5 mm as in previous works [6,10]. A RANS (Reynolds Averaged Navier-Stokes) approach is used for simulating the turbulence.…”

Section: Model Descriptionmentioning

confidence: 99%

“…These aspects are covered by flamelet models used together with tabulated chemistry and, more particularly, by the Approximated Diffusion Flamelet (ADF) approach [4]. This model, used in the present work, has been demonstrated to offer powerful capabilities and provides satisfactory results in the frame of diesel sprays and diesel engines simulations [5,6]. Nevertheless, the fuel oxidation process, given by the chemical mechanism, arises as one of the cornerstones in the combustion numerical simulation and is one of the inputs to the problem which causes a greater uncertainty.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Influence of the chemical mechanism in the frame of diesel-like CFD reacting spray simulations using a presumed PDF flamelet-based combustion model

González

Oliver

Novella

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The ability of a computational fluid dynamics (CFD) simulation to reproduce the diesel-like reacting spray ignition process and its corresponding flame structure strongly depends on both the fidelity of the chemical mechanism for reproducing the oxidation of the fuel and also on how the turbulence-chemistry interaction (TCI) is modeled. Therefore, investigating the performance of different chemical mechanisms not only in perfect stirred reactors but directly in the diesel-like spray itself is of great interest in order to evaluate their suitability for being further applied to CFD engine simulations. This research work focuses on applying a presumed probability density function (PDF) unsteady flamelet combustion model to the well-known spray A from the Engine Combustion Network (ECN), using three chemical mechanisms widely accepted by the scientific community as a way to figure out the influence of chemistry in the key characteristics of the combustion process in the frame of diesel-like spray simulations. Results confirm that in spite of providing all of them correct trends for ignition delays (ID) and lift-off lengths (LOL), when comparing with experimental results, the structure of the flame presents noticeable differences, especially in the low and intermediate temperatures and high equivalence ratio regions. Consequently, the selection of the chemical mechanism has an impact on the zones of influence of key species as observed in both spatial coordinates and also in the equivalence ratio-temperature maps. These differences are expected to be relevant considering the implications when coupling pollutant emissions models. The analysis of temperature and oxygen concentration parametric studies evidences how the observed differences are consistent and moderately dependent on the ambient conditions. KeywordsCombustion modeling, Chemical mechanism, Spray A, Flamelet IntroductionThe improvement of the combustion technologies in industrial devices, such as diesel engines, in terms of efficiency and pollutant emissions, evidence that a comprehensive knowledge of the processes involved is mandatory. Between the different processes that concur in the energetic transformation, turbulent non-premixed combustion appears as one of the most relevant. Nevertheless, its modeling is a complex issue due to the different length and time scales of the turbulence, the fuel oxidation and the interaction between them [1]. These considerations point out that for a proper modeling of the turbulent non-premixed combustion two main aspects are essential. The first one is the chemical mechanism, that determines the fuel oxidation, while the second one is the turbulence-chemistry interaction (TCI). Promoted by the need of gaining a very detailed knowledge in these issues in diesel spray conditions, the Engine Combustion Network (ECN) has proposed a set of experiments in controlled conditions that shed light for these concerns by means of experiments and numerical simulations. More particularly, the well-known spray A models a die...

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“…The injection rate lasts for more than 4 ms in order to describe the quasi-steady fields. More details about the injection rate can be found in [6,20]. …”

Section: Parametric Studymentioning

confidence: 99%