Numerical analysis of the Cambridge stratified flame series using artificial thickened flame LES with tabulated premixed flame chemistry

Proch, Fabian; Kempf, Andreas

doi:10.1016/j.combustflame.2014.04.010

Cited by 114 publications

(77 citation statements)

References 55 publications

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“…Such an endeavor requires a concerted community effort, by which the herein proposed Wasserstein metric could come to use as a quantitative measure. It is noted that several of these TNFcontributions have been extended since, and we would like to refer to publications [61,62,53,63,64,65,66], which provide further details on the validation and analysis of simulation results, as well as description of combustion models and computational setups of individual groups.…”

Section: Quantitative Comparison Of Different Simulation Resultsmentioning

confidence: 99%

A general probabilistic approach for the quantitative assessment of LES combustion models

Johnson

Ihme

2017

Combustion and Flame

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The Wasserstein metric is introduced as a probabilistic method to enable quantitative evaluations of LES combustion models. The Wasserstein metric can directly be evaluated from scatter data or statistical results using probabilistic reconstruction against experimental data. The method is derived and generalized for turbulent reacting flows, and applied to validation tests involving the Sydney piloted jet flame. It is shown that the Wasserstein metric is an effective validation tool that extends to multiple scalar quantities, providing an objective and quantitative evaluation of model deficiencies and boundary conditions on the simulation accuracy. Several test cases are considered, beginning with a comparison of mixture-fraction results, and the subsequent extension to reactive scalars, including temperature and species mass fractions of CO and CO 2 . To demonstrate the versatility of the proposed method in application to multiple datasets, the Wasserstein metric is applied to a series of different simulations that were contributed to the TNF-workshop. Analysis of the results allowed to identify competing contributions to model deviations, arising from uncertainties in the boundary conditions and model deficiencies. These applications demonstrate that the Wasserstein metric constitutes an easily applicable mathematical tool that reduce multiscalar combustion data and large datasets into a scalar-valued quantitative measure.

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Section: Quantitative Comparison Of Different Simulation Resultsmentioning

confidence: 99%

A general probabilistic approach for the quantitative assessment of LES combustion models

Johnson

Ihme

2017

Combustion and Flame

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“…Detailed velocity and scalar data sets are now available for two burners [14,15] designed to have relatively simple geometries and flow fields and to isolate effects of mixture stratification in back-supported, fuel-lean turbulent combustion. Simulations of these flames have been carried out by several groups [16][17][18], achieving reasonably good success without explicitly modeling the effects of the instantaneous mixture fraction gradient on local flame structure. There have also been significant efforts to develop approaches for modeling partially-premixed combustion that includes both premixed and diffusion-controlled reaction zones, particularly in the context of flamelet-based tabulation methods in large eddy simulation (LES) [19,20].…”

Section: Introductionmentioning

confidence: 99%

Local extinction and near-field structure in piloted turbulent CH4/air jet flames with inhomogeneous inlets

Barlow

Meares

Magnotti

et al. 2015

Combustion and Flame

100

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a b s t r a c tLine-imaged measurements of temperature and major species, based on well-established Raman/Rayleigh/CO-LIF techniques, are used to better understand the scalar structure of piloted CH 4 /air jet flames with inhomogeneous inlets. Recent studies using a variant of the Sydney piloted burner have demonstrated that the blowoff velocity of a partially-premixed jet flame of CNG or CH 4 and air can be increased significantly by tailoring the mixture fraction profile at the burner exit. This is done by adding a small, retractable central tube within the main tube of the burner and separately supplying fuel and air for partial premixing. Both tubes are located within the pilot annulus. When the central tube is retracted far upstream of the burner exit, the flame has the same stability as that of the original burner with homogeneous fuel-air composition at the jet exit. However, when the inner tube supplies fuel and is retracted an optimal distance (10-13 times the main tube diameter) the blowoff velocity is increased by nearly 40%. Previous results indicated that combustion very close to the burner exit occurs in a stratified-premixed mode, augmenting the stabilizing effect of the pilot. This is followed by transition to a diffusion-dominated mode of burning within the first ten main tube diameters.The present paper provides a detailed examination of a series of piloted CH 4 /air jet flames with different inlet conditions and with a pilot flame that matches the composition and adiabatic flame temperature of CH 4 /air. It addresses trends in local extinction as well as differences in near-field flame structure. The evolution in the local mode of combustion is traced using instantaneous line-imaged realizations where the change in mixture fraction across a 1000 K interval is used as a conditioning variable. Doubly conditioned means of selected species mass fractions confirm that the flames with inhomogeneous inlet profiles undergo transition from a stratified-premixed mode of combustion to a diffusion-dominated mode of combustion within the first ten jet diameters. Calculations of strained laminar partially-premixed flames are used to gain insight on the effects of strain rate and fuel-side equivalence ratio on flame structure and the rate of heat release. These turbulent jet flames may serve as interesting test cases for models aimed at predicting the performance of practical burners that operate with mixed combustion modes.

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“…Large eddy simulation is now a practical tool for modelling the interaction of turbulence and chemistry and previous numerical investigations into the non-swirling flames of the Cambridge Stratified Swirl Burner have been conducted, using various flamelet approaches, by amongst others [7] and [8]. The flames considered, while turbulent, have relatively low Reynolds numbers with the consequence that sgs fluctuations are often negligible over substantial regions of the flames.…”

Section: Introductionmentioning

confidence: 99%

LES of the Cambridge Stratified Swirl Burner using a Sub-grid pdf Approach

Brauner

Jones

Marquis

2016

Flow Turbulence Combust

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The sub-grid scale probability density function equation is rearranged in order to separate the resolved and sub-grid-scale (sgs) contributions to the sgs mixing term. This allows modelling that is consistent with the limiting case of negligible sub-grid scale variations, a property required for applications to laboratory premixed flames. The new method is applied to the Cambridge Stratified Swirl Burner for 6 operating conditions, 2 isothermal and 4 burning, with varying degrees of swirl and mixture stratification. The simulations are performed with the Large Eddy Simulation (LES) code BOFFIN in which the modelled pdf transport equation is solved using the Eulerian stochastic field method. Eight stochastic fields are used to account for the influence of the sub-grid fluctuations and the chemistry is modelled with a reduced version of the GRI 3.0 mechanism for methane involving 19 species and 15 reaction steps. The simulated velocities for both the isothermal and burning cases show good agreement with the experimental data. The measured temperature and major species profiles are also reproduced to a good accuracy.

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Numerical analysis of the Cambridge stratified flame series using artificial thickened flame LES with tabulated premixed flame chemistry

Cited by 114 publications

References 55 publications

A general probabilistic approach for the quantitative assessment of LES combustion models

A general probabilistic approach for the quantitative assessment of LES combustion models

Local extinction and near-field structure in piloted turbulent CH4/air jet flames with inhomogeneous inlets

LES of the Cambridge Stratified Swirl Burner using a Sub-grid pdf Approach

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