A multiscale combustion model formulation for NO  predictions in hydrogen enriched jet flames

Iavarone, Salvatore; Cafiero, Marianna; Ferrarotti, Marco; Contino, Francesco; Parente, Alessandro

doi:10.1016/j.ijhydene.2019.07.019

Cited by 34 publications

(31 citation statements)

References 79 publications

(115 reference statements)

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“…This overestimation is likely due to the absence of the reburning route and the assumption of a global scheme for the prompt route, which was found to be the main contributor to NO formation in the corresponding study (Galletti et al, 2015). For models M5-M6, Iavarone et al (2019) found that the contribution of each pathway to the peak of NO formation at z = 200 mm is as follows (in decreasing order): NNH>thermal>prompt>N 2 O. The analysis has been extended to the other two axial locations: at z = 60 mm the rank is prompt>NNH>N 2 O>thermal, whereas at z = 120 mm the NNH contribution overcomes the prompt one and the rank is thus NNH>prompt>N 2 O>thermal.…”

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 94%

“…In PaSR, a reacting region volume fraction κ is defined based on local estimations of chemical and mixing time scales. Better results in terms of predicted temperatures and main species concentrations in the Adelaide JHC burner have been achieved by both Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) studies employing the PaSR model Ferrarotti et al, 2019;Iavarone et al, 2019) with respect to EDC. However, estimating the formation of NO x may require the resolution of chemical source terms with different characteristic time scales, since the reactions forming NO occur in a wider range of time scales compared to those of the main combustion process.…”

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

“…However, estimating the formation of NO x may require the resolution of chemical source terms with different characteristic time scales, since the reactions forming NO occur in a wider range of time scales compared to those of the main combustion process. Thus, a PaSR formulation that relates the source terms of the NO x species to their formation time scales, resulting in different values of κ for the NO x species, was presented (Iavarone et al, 2019). Figure 2 provides a comparison of the capabilities of some of the CFD modeling approaches mentioned above to replicate the emission of NO x measured in the Adelaide JHC burner.…”

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

“…Models M5 and M6 employ the PaSR model and the GRI2.11 scheme. Model M5 consider a single value of κ in the PaSR formulation for all the species, whereas model M6 uses additional specific values of κ for the NO x species, as put forth by Iavarone et al (2019).…”

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

“…A slight overestimation persists at z = 120 mm, along with a displacement of the NO profile. The latter is due to the shift of the predicted profiles of relevant quantities for NO x formation, such as temperature and OH concentration, reported in Iavarone et al (2019). The cause may be attributed not only to the kinetic mechanism and the combustion model employed, but also to the choice of the turbulence model, which must be able the replicate the spreading of the jet flame.…”

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

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NOx Formation in MILD Combustion: Potential and Limitations of Existing Approaches in CFD

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2020

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Emissions of nitrogen oxides (NO x ) from combustion systems remain a lingering environmental issue, being these species either greenhouse gases or acid rain precursors. Moderate or Intense Low-oxygen Dilution (MILD) combustion can reduce the emissions of NO x thanks to its characteristic features (i.e., homogeneous reaction zones, reduced temperature peaks, diluted mixtures of reactants) that influence and change the main chemical pathways of NO x formation. A summary of the relevant routes of formation and destruction of NO x in MILD combustion is presented in this review, along with the identification of the sources of uncertainty that prevent reaching an overall consensus in the literature about the dominant NO x chemical pathway in MILD regime. Computational Fluid Dynamics (CFD) approaches are essential tools for investigating the critical phenomena occurring in MILD combustion and the design of pollutant-free turbulent combustion systems. This paper provides an outline of the modeling approaches employed in CFD simulations of turbulent combustion systems to predict NO x emissions in MILD conditions. An assessment of the performances of selected models in estimating NO x formation in a lab-scale MILD combustion burner is then presented, followed by a discussion about relevant modeling issues, perspectives and opportunities for future research.

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Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 94%

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

Section: Cfd Modeling Of No X Emissions In Mild Conditionsmentioning

confidence: 99%

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NOx Formation in MILD Combustion: Potential and Limitations of Existing Approaches in CFD

Iavarone

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2020

Front. Mech. Eng.

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Supervised Clustering for Optimal Sub-model Selection in Reactor-Based Models

Péquin

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Flow Turbulence Combust

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Reactor-based models are well-suited Turbulence-Chemistry Interactions (TCI) Sub-Grid Scale (SGS) closures for Large Eddy Simulation (LES) due to their ability to account for finite-rate kinetics. The Partially Stirred Reactor (PaSR) model relies on the estimation of characteristic time scales to define the reacting fraction of each computational cell. However, chemistry develops a spectrum of intrinsic chemical time scales, leaving no clear consensus on the definition of a single representative scale. Nevertheless, in numerical codes, a single chemical time scale formulation is used on the whole physical domain despite local and complex phenomena. Through an a priori assessment on Direct Numerical Simulation (DNS) data of turbulent non-premixed combustion, the present work proposes a numerical method to locally select an optimal chemical time scale formulation that minimises the model error. Data points are grouped into clusters via supervised partitioning algorithms where the optimal formulation is attributed to each cluster by means of distances minimisation. Using a combination of partitioning procedures can further improve the reconstruction quality of the clustered solutions, up to 35% global errors reductions with respect to standard solutions. Existing data partitions are then tested on unseen data points, yielding great prediction capabilities across grid

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Direct numerical simulations of flameless combustion

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A multiscale combustion model formulation for NO predictions in hydrogen enriched jet flames

Cited by 34 publications

References 79 publications

NOx Formation in MILD Combustion: Potential and Limitations of Existing Approaches in CFD

NOx Formation in MILD Combustion: Potential and Limitations of Existing Approaches in CFD

Supervised Clustering for Optimal Sub-model Selection in Reactor-Based Models

Direct numerical simulations of flameless combustion

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