The influence of chemical mechanisms on PDF calculations of nonpremixed piloted jet flames☆

Cao, Renfeng Richard; Pope, Stephen B.

doi:10.1016/j.combustflame.2005.08.018

Cited by 123 publications

(71 citation statements)

References 20 publications

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“…Details and limits about it can be found in the literature [16,[23][24][25]. BI T is generally calculated as the ratio of the difference between local instantaneous temperature and room temperature, and the difference between reference temperature and room temperature.…”

Section: Fig 2 Pictures Of A-series Flames (Left) B-series Flames mentioning

confidence: 99%

On the structure of the near field of oxy-fuel jet flames using Raman/Rayleigh laser diagnostics

Sevault

Dunn

Ditaranto

2012

Combustion and Flame

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An experimental study on turbulent non-premixed jet flames is presented with focus on CO 2 -diluted oxy-fuel combustion using a coflow burner. Measurements of local temperatures and concentrations of the main species CO 2 , O 2 , CO, N 2 , CH 4 , H 2 O and H 2 were achieved using the simultaneous line-imaged Raman/Rayleigh laser diagnostics setup at Sandia National Laboratories. Two series of flames burning mixtures of methane and hydrogen were investigated. In the first series, the hydrogen molar fraction in the fuel was varied from 37 to 55 %, with a constant jet exit Reynolds number Re Fuel of 15,000. In the second series the jet exit Reynolds number was varied from 12,000 to 18,000, while keeping 55 % H 2 molar fraction in the fuel. Besides local temperatures and concentrations, the results revealed insights on the behaviour of localized extinction in the near-field. It was observed that the degree of extinction increased as the hydrogen content in fuel was decreased and as the jet Reynolds number was increased. Based on the distribution of the temperature, a fully burning probability index able to quantify the degree of extinction along the streamwise coordinate was defined and applied to the present flame measurements. A comparison of measured conditional mean of mass fractions and laminar flame calculations underlined the significant level of differential diffusion in the near-field that tended to decrease farther downstream. The results also showed high local CO levels induced by the high content of CO 2 in the oxidizer and flame products. A shift of maximum flame temperature was observed toward the rich side of the mixture fraction space, most likely as a consequence of reduced heat release in the presence of product dissociation. Main characteristics of laser Raman scattering measurements in CO 2 -diluted oxy-fuel conditions compared to air-diluted conditions are also highlighted. Most data, including scalar fluctuations and conditional statistics are available upon request.

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Section: Fig 2 Pictures Of A-series Flames (Left) B-series Flames mentioning

confidence: 99%

On the structure of the near field of oxy-fuel jet flames using Raman/Rayleigh laser diagnostics

Sevault

Dunn

Ditaranto

2012

Combustion and Flame

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“…For this purpose we select the partially premixed diffusion flame, Sandia Flame D. For this flame a large amount of experimental information is available [12,13]. The flame has also been simulated many times, both LES [14][15][16][17][18][19][20][21] and RANS [22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Subgrid Scale Modeling in Large-Eddy Simulation of Turbulent Combustion Using Premixed Flamelet Chemistry

Vreman

Oijen

Goey

et al. 2008

Flow Turbulence Combust

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Large-eddy simulation (LES) of turbulent combustion with premixed flamelets is investigated in this paper. The approach solves the filtered NavierStokes equations supplemented with two transport equations, one for the mixture fraction and another for a progress variable. The LES premixed flamelet approach is tested for two flows: a premixed preheated Bunsen flame and a partially premixed diffusion flame (Sandia Flame D). In the first case, we compare the LES with a direct numerical simulation (DNS). Four non-trivial models for the chemical source term are considered for the Bunsen flame: the standard presumed beta-pdf model, and three new propositions (simpler than the beta-pdf model): the filtered flamelet model, the shift-filter model and the shift-inversion model. A priori and a posteriori tests are performed for these subgrid reaction models. In the present preheated Bunsen flame, the filtered flamelet model gives the best results in a priori tests. The LES tests for the Bunsen flame are limited to a case in which the filter width is only slightly larger than the flame thickness. According to the a posteriori tests the three models (beta-pdf, filtered flamelet and shift-inversion) show more or less the same results as the trivial model, in which subgrid reaction effects are ignored, while the shift-filter model leads to worse results. Since LES needs to resolve the large turbulent eddies, the LES filter width is bounded by a maximum. For the present Bunsen flame this means that the filter width should be of the order of the flame thickness or smaller. In this regime, the effects of subgrid reaction and subgrid flame wrinkling turn out to be quite modest. The LES-results of the second case (Sandia Flame D) are compared to experimental data. Satisfactory agreement is obtained for the main species. Comparison is made between different eddy-viscosity models for the subgrid turbulence, and the Smagorinsky eddy-viscosity is found to give worse results than eddy-viscosities that are not dominated by the mean shear.

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“…The Sandia piloted jet flames (Barlow and Frank, 1998) Vogiatzaki et al (2011) in order to determine the value of modelling parameters which give the best agreement with conditional variance of temperature and various species mass fractions. Previous studies using transported PDF methods in RANS have produced good agreement with experiment (Lindstedt et al, 2000;Xu and Pope, 2000) for Flame F and also revealed the sensitivity of this Flame F to the chosen chemical mechanism (Cao and Pope, 2005). These studies were useful in determining the parameters needed in RANS-PDF modelling to give accurate results, a process that is now being undertaken for LES studies.…”

Section: Introductionmentioning

confidence: 54%

“…This mechanism is a systematically reduced version of the GRI mechanism where 19 reactive species plus temperature and 15 steps (Sung et al, 1998). This mechanism has previously been found to give good accuracy without a prohibitive computational cost in Cao and Pope (2005).…”

Section: Chemical Source Termmentioning

confidence: 99%

Sensitivity analysis of LES–CMC predictions of piloted jet flames

Garmory

Mastorakos

2013

International Journal of Heat and Fluid Flow

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The influence of chemical mechanisms on PDF calculations of nonpremixed piloted jet flames☆

Cited by 123 publications

References 20 publications

On the structure of the near field of oxy-fuel jet flames using Raman/Rayleigh laser diagnostics

On the structure of the near field of oxy-fuel jet flames using Raman/Rayleigh laser diagnostics

Subgrid Scale Modeling in Large-Eddy Simulation of Turbulent Combustion Using Premixed Flamelet Chemistry

Sensitivity analysis of LES–CMC predictions of piloted jet flames

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