Thirteenth International Workshop on Measurement and Computation of Turbulent Flames (TNF2016)

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doi:10.2172/1505369

Cited by 3 publications

(8 citation statements)

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“…The process level is split into three main blocks, namely, experiments, highly resolved LES and DNS, respectively, of (at least partially) isolated engine processes on a laboratory scale. This level is most important, and in fact, this is where the most fruitful experimental-numerical collaborations already exist, for example, in the ECN, 13 the TNF workshop 108 or the International Sooting Flame (ISF) workshop. 109 In contrast to previous definitions of the process level, for engines both experiments and simulations (LES and DNS) can serve as a data source.…”

Section: Approach For Systematic Model Evaluation and Development Formentioning

confidence: 99%

“…For engine combustion, the limits between unit problems and process level are continuous; for instance, the DNS of a stratified flame 126 could be attributed to both levels, for example, if the stratification in the DNS is close to a mixture condition identified in step 1. A review of available DNS datasets, mostly at the unit-problem level, can be found in Barlow et al 108 Although the discussion is deliberately kept generic here, it is clear that the approach described above ensures that the process initially starts on the system level (step 1), then consecutively steps down the pyramid (steps 2-6) before it finally returns to the system level (step 7; see Figures 4 and 5).…”

Section: Approach For Systematic Model Evaluation and Development Formentioning

confidence: 99%

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Scale-resolving simulations in engine combustion process design based on a systematic approach for model development

Hasse

2015

International Journal of Engine Research

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The increasing availability of high-performance computing resources will allow scale-resolving simulations such as large eddy simulations to be used instead of unsteady Reynolds-averaged Navier-Stokes approaches, not only in academic research but also for engine combustion process development. The scope of this work is to highlight and discuss this transition to scale-resolving simulations and to propose a systematic approach for model development and application. The current and future scope of industrial and academic research is discussed especially with respect to cycle-to-cycle variations, which cannot be identified with unsteady Reynolds-averaged Navier-Stokes models. The individual processes along the cause-and-effect chain leading to cyclic variations of the combustion process are identified, and the current state of scale-resolving simulations and the required models with respect to these processes are discussed.

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Section: Approach For Systematic Model Evaluation and Development Formentioning

confidence: 99%

Section: Approach For Systematic Model Evaluation and Development Formentioning

confidence: 99%

Scale-resolving simulations in engine combustion process design based on a systematic approach for model development

Hasse

2015

International Journal of Engine Research

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“…The Wasserstein metric has been employed to assess different modeling approaches in simulating a turbulent jet flame with inhomogeneous inlets. 31,32 Representative results are illustrated in fig. 5, showing comparisons of the multiscalar Wasserstein metric for QoIs of mixture fraction, temperature, and species mass fractions of CO 2 and CO.…”

Section: How To Assess the Simulation Accuracy?mentioning

confidence: 99%

“…Figure 5: Quantitative evaluation of multiscalar Wasserstein metric, 31 W2(Z, T, YCO 2 , YCO) from six different LEScalculations of the piloted turbulent CH4/air jet flame with inhomogeneous inlets; results presented at the 14th TNF-workshop. 32 The metric decomposition allows to assess contributions from each scalar quantity for all axial location. This quantitative validation analysis enables models to be compared objectively.…”

Section: How To Assess the Simulation Accuracy?mentioning

confidence: 99%

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Requirements Towards Predictive Simulations of Turbulent Combustion

Ihme

2019

AIAA Scitech 2019 Forum

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Significant progress has been made on the development of modeling approaches for simulating turbulent reacting flows. We are currently in a position where keyphysical aspects of fairly complex combustion processes are reasonably well understood at a qualitative and-in many cases-also at a quantitative level. Examples are the prediction of temperature and major species, statistically stationary flames, gaseous combustion, turbulence/flame coupling, and turbulent scalar transport. However, major challenges arise in capturing transient processes, minor species, multi-phase flows, and multidimensional flame/flow interactions. With this, the question arises what steps need to be taken to elevate the current state of modeling capabilities to address these deficiencies? This paper seeks to address this multifaceted question. For this, we begin by briefly reviewing the current state of combustion model approaches, our quest for improving existing models, and ideas on model evaluations. We then proceed by examining concepts on quantitative model evaluations, requirements on predictability, quantities of interest, and cost/accuracy trade-offs. We close by introducing recent concepts on model evaluations that directly incorporate time-resolved measurements.

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Analysis of Flame Front Breaks Appearing in LES of Inhomogeneous Jet Flames Using Flamelets

Soli

Langella

Chen

2021

Flow Turbulence Combust

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The physical mechanism leading to flame local extinction remains a key issue to be further understood. An analysis of large eddy simulation (LES) data with presumed probability density function (PDF) based closure (Chen et al., 2020, Combust. Flame, vol. 212, pp. 415) indicated the presence of localised breaks of the flame front along the stoichiometric line. These observations and their relation to local quenching of burning fluid particles, together with the possible physical mechanisms and conditions allowing their appearance in LES with a simple flamelet model, are investigated in this work using a combined Lagrangian-Eulerian analysis. The Sidney/Sandia piloted jet flames with compositionally inhomogeneous inlet and increasing bulk speeds, amounting to respectively 70 and 90% of the experimental blow-off velocity, are used for this analysis. Passive flow tracers are first seeded in the inlet streams and tracked for their lifetime. The critical scenario observed in the Lagrangian analysis, i.e., burning particles crossing extinction holes on the stoichiometric iso-surface, is then investigated using the Eulerian control-volume approach. For the 70% blow-off case the observed flame front breaks/extinction holes are due to cold and inhomogeneous reactants that are cast onto the stoichiometric iso-surface by large vortices initiated in the jet/pilot shear layer. In this case an extinction hole forms only when the strain effect is accompanied by strong subgrid mixing. This mechanism is captured by the unstrained flamelets model due to the ability of the LES to resolve large-scale strain and considers the SGS mixture fraction variance weakening effect on the reaction rate through the flamelet manifold. Only at 90% blow-off speed the expected limitation of the underlying combustion model assumption become apparent, where the amount of local extinctions predicted by the LES is underestimated compared to the experiment. In this case flame front breaks are still observed in the LES and are caused by a stronger vortex/strain interaction yet without the aid of mixture fraction variance. The reasons for these different behaviours and their implications from a physical and modelling point of view are discussed in this study.

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Thirteenth International Workshop on Measurement and Computation of Turbulent Flames (TNF2016)

Cited by 3 publications

References 0 publications

Scale-resolving simulations in engine combustion process design based on a systematic approach for model development

Scale-resolving simulations in engine combustion process design based on a systematic approach for model development

Requirements Towards Predictive Simulations of Turbulent Combustion

Analysis of Flame Front Breaks Appearing in LES of Inhomogeneous Jet Flames Using Flamelets

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