The coupling of turbulence and chemistry in a premixed bluff-body flame as studied by LES

Giacomazzi, E.; Battaglia, Valerio; Bruno, Claudio

doi:10.1016/j.combustflame.2004.06.004

Cited by 111 publications

(73 citation statements)

References 16 publications

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“…When bluff body is used as a flame holder, the incoming fuel and oxidizer mixture is ignited by the hot combustion products recirculating in a wake structure formed behind the bluff body. This stabilization mechanism has been investigated extensively by many researchers [6][7][8][9][10][11][12]. Many studies associated with bluff body stabilization mechanism focus on premixed combustion systems, where premixed fuel and oxidizer are provided to the combustion zone and thus complex physics that controls mixing process can be neglected.…”

Section: Ppbb Burnermentioning

confidence: 99%

Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner

2015

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Abstract:In this study, the influence of various factors on nitrogen oxides (NOx) emissions of a low NOx burner is investigated using a central composite design (CCD) approach to an experimental matrix in order to show the applicability of design of experiments methodology to the combustion field. Four factors have been analyzed in terms of their impact on NOx formation: hydrogen fraction in the fuel (0%-15% mass fraction in hydrogen-enriched methane), amount of excess air (5%-30%), burner head position (20-25 mm from the burner throat) and secondary fuel fraction provided to the burner (0%-6%). The measurements were performed at a constant thermal load equal to 25 kW (calculated based on lower heating value). Response surface methodology and CCD were used to develop a second-degree polynomial regression model of the burner NOx emissions. The significance of the tested factors over their respective ranges has been evaluated using the analysis of variance and by the consideration of the coefficients of the model equation. Results show that hydrogen addition to methane leads to increased NOx emissions in comparison to emissions from pure methane combustion. Hydrogen content in a fuel is the strongest factor affecting NOx emissions among all the factors tested. Lower NOx formation because of increased excess air was observed when the burner was fuelled by pure methane, but this effect diminished for hydrogen-rich fuel mixtures. NOx emissions were slightly reduced when the burner head was shifted closer to the burner outer tube, whereas a OPEN ACCESSEnergies 2015, 8 3607 secondary fuel stream provided to the burner was found to have no impact on NOx emissions over the investigated range of factors.

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Section: Ppbb Burnermentioning

confidence: 99%

Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner

2015

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“…The terms on the right-hand side represent the effects of strain, propagation and differential propagation respectively. A simplified equation to (12) has been obtained by Weller [8] as:…”

Section: Turbulent Combustion Modelingmentioning

confidence: 99%

Validation Study of Large-Eddy Simulations of Wake Stabilized Reacting Flows using Artificial Flame Thickening Approaches

Kewlani

Vogiatzaki

Shanbhogue

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Wake flows are the preferred mode of flame stabilization in lean premixed combustion in gas turbine engines, low NOx burners, afterburners etc. These flows exhibit inherent unsteadiness and for their numerical modeling and simulations, large eddy simulation (LES) techniques with an appropriate combustion model and reaction mechanism afford a balance between computational complexity and predictive accuracy. Before using them in practical systems, these techniques must be validated against experimental measurements in a number of canonical cases. In this work, results from LES of non-reacting and reacting flows are compared to data from a number of experiments, corresponding to the following configurations: a triangular bluff body in a rectangular duct, a backward facing step, and a cylindrical sudden expansion with swirl. The artificial flame thickening approach is applied for modeling turbulence-combustion interactions at small scales. Algebraic and equationbased efficiency function models are implemented, along with an appropriate reduced chemistry mechanism. A novel dynamic formulation for the efficiency function based on the flame-wrinkling equation that explicitly incorporates the influence of strain and time-history effects is proposed, and a detailed combustion chemistry mechanism is also used. Results show that the approaches are effective in simulating turbulent premixed combustion. Permanent repository link

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“…LES of premixed flame has been applied in laboratorial scale [21] and even close to industrial application [22], with the rapid progress of computation ability. Moreover, to satisfy the requirement of modeling auto-ignition and slowscale pollutants production in turbulent premixed flame, it has been believed that reduced mechanism with modest number of species will be initially used.…”

Section: Les Of Turbulent Bunsen Flamementioning

confidence: 99%

“…Eddy-dissipation-concept (EDC) model [26] was adopted to account for combustion in subgrid. Detailed explanation can be found in [21]. For simplicity, LES was implemented in 2D based on finite-volume method.…”

Section: Les Of Turbulent Bunsen Flamementioning

confidence: 99%

Systematic method of applying ANN for chemical kinetics reduction in turbulent premixed combustion modeling

Zhao

Wang

et al. 2012

Chin. Sci. Bull.

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A novel method to apply artificial neural network (ANN) for both chemical kinetics reduction and source term evaluation is introduced and tested in direct numerical simulation (DNS) and large eddy simulation (LES) of reactive flows. To gather turbulence affected flame data for ANN training, a new computation-economical method, called 1D pseudo-velocity disturbed flame (PVDF), is developed and used to generate thermo-chemical states independent of the modeled flame. Then a back-propagation ANN is trained using scaled conjugate gradient algorithm to memorize the sample states with reduced orders. The new method is employed in DNS and LES modeling of H 2 /air and C 3 H 8 /air premixed flames experiencing various levels of turbulence. The test result shows that compared to traditional computation with full mechanism and direct integration, this method can obtain quite large speed-ups with adequate prediction accuracy. [7,8] are often used, while ANN method, a extremely new systemic technique, is seldom seen in previous work. The procedure of using QSS assumption has been shown in Figure 1. However, QSS species concentrations should be first resolved which includes a large amount of algebraic iterations. Therefore, the net efficiency could be undermined [9], and also calculation may be failed if iterations do not converge. ANN, kinetics reduction, LES, DNSAs for the second respect, several approaches to accelerate chemical sources evaluation have already been presented, such as look-up table (LUT) [10] and in situ-adaptive tabulation (ISAT) [11]. However, they are both based on tabulation technique which needs huge memory and a large number of check-up and interpolation operations. Artificial neural network (ANN) method, although it was proposed previously to handle above drawbacks, has got great progress through Sen and Menon's work [12,13]. It has been successfully applied to account for chemical kinetics in LES modeling of turbulent premixed flame with speed-ups even more than 10.In this paper, we tend to extend the application of ANN method, using it to not only calculate chemical sources but also reduce the detailed mechanism. The initial idea is to construct the direct mapping between non-QSS species concentrations and their reaction rates at plenty of thermal

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The coupling of turbulence and chemistry in a premixed bluff-body flame as studied by LES

Cited by 111 publications

References 16 publications

Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner

Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner

Validation Study of Large-Eddy Simulations of Wake Stabilized Reacting Flows using Artificial Flame Thickening Approaches

Systematic method of applying ANN for chemical kinetics reduction in turbulent premixed combustion modeling

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