The structure of turbulent stratified and premixed methane/air flames II: Swirling flows

Sweeney, Mark; Hochgreb, Simone; Dunn, Matthew J.; Barlow, Robert S.

doi:10.1016/j.combustflame.2012.05.014

Cited by 146 publications

(98 citation statements)

References 41 publications

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“…The results of the experiments are reported in [5,6,26]. The burner consists of a central bluff body surrounded by two concentric annular channels and a co-flow assembly to prevent entrainment of ambient air.…”

Section: Cambridge Stratified Swirl Burner and Computational Setupmentioning

confidence: 99%

“…The Cambridge Stratified Swirl Burner [5,6] provides a flame series that allows for the numerical investigation of flames operating at laboratory conditions closer to those of an industrial configuration, while providing detailed experimental data against which to validate models. 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].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Cambridge Stratified Swirl Burner and Computational Setupmentioning

confidence: 99%

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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“…In the present paper, the flow field within the CSB which has a central bluff-body designed by Sweeney et al [35,36] was investigated. Detailed measurements of the flow fields and the scalars field make this burner a well benchmark case for gaining an in-depth understanding of large-scale structures in swirling flow and improving exiting modeling capabilities.…”

Section: Introductionmentioning

confidence: 99%

“…All the fluid in two annular slots and coflow is air at room temperature and atmospheric pressure. Detailed measurements of the flow fields have been carried out by Sweeney et al [35,36] and Zhou et al [37]. The operating conditions considered in the present numerical cases are listed in Table 1, where U j is the annular jet velocity, U s is the bulk axial velocity of the annular swirling flow, W s is the bulk circumferential velocity of the annular swirling flow, U e is the external coflow velocity, Re j and Re s are the Reynolds numbers of the jet and swirling flow, respectively.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of unconfined turbulent swirling flow

Zhang

Han

et al. 2015

Sci. China Technol. Sci.

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Large eddy simulations (LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of experimental data show that the LES results are capable of predicting mean and root-mean-square velocity profiles. The LES results show that the annular swirling flow has a minor impact on the formation of the bluff-body recirculation zone. The vortex structures near the shear layers, visualized by the iso-surface of Q-criterion, display ring structures in non-swirling flow and helical structures in swirling flow near the burner exit. Spectral analysis was employed to predict the occurrence of flow oscillations induced by vortex shedding and precessing vortex core (PVC). In order to extract accurately the unsteady large-scale structures in swirling flow, a three-dimensional proper orthogonal decomposition (POD) method was developed to reconstruct turbulent fluctuating velocity fields. POD analysis reveals that flow fields contain co-existing helical and toroidal shaped coherent structures. The helical structure associated with the PVC is the most energetic dynamic flow structure. The latter toroidal structure associated with vortex shedding has lower energy content which indicates that it is a secondary structure. Cambridge swirl burner, large eddy simulation, proper orthogonal decomposition, vortex shedding and breakdown, precessing vortex core Citation: Zhang H D, Han C, Ye T H, et al. Large eddy simulation of unconfined turbulent swirling flow.

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“…The comprehensive research of the confined swirling flows includes an experimental study and a numerical analysis of the development of the downstream flow structure and combustion dynamics by varying the flow geometry, boundary conditions and swirl intensity [1][2][3][4][5]. These studies have shown that relatively small variations of the inlet conditions and configuration of the swirl combustor can result in unpredictable variations of the flow patterns and main flame characteristics.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study of the development of swirling flow and flame dynamics and combustion characteristics at biomass thermo-chemical conversion

Barmina¹,

Valdmanis²,

Kalis³

et al. 2017

Engineering for Rural Development

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Abstract. The focus of this study is to investigate the main factors determining the development of swirling flow dynamics and to correlate the development of the non-premixed swirling flame characteristics at biomass thermo-chemical conversion with the evolution of the confined swirling flow velocity fields in a pilot device which combines a biomass gasifier and a combustor. This study includes complex experimental study and numerical modelling of the development of velocity fields for confined non-reacting swirling flows and flame, as well as the development of swirling flame velocity fields and combustion characteristics at biomass thermochemical conversion under effects of various inlet conditions, such as the inlet nozzle diameter at the bottom of the combustor, primary and swirling air supply rates in the device. The results show that the development of the swirling flow velocity field first of all is closely related to the inlet nozzle diameter, which for the fixed primary and secondary air supply rates strongly affects the upstream and downstream swirling airflow formation and swirl intensity, which are highly responsible for the mixing of combustible volatiles with the axial air flow, for the ignition and combustion of volatiles. The results also show that the development of the swirling flow velocity field depends on the air supply rate which affects the development of the combustion dynamics and composition of emission through the variation of the downstream flow structure and the air excess ratio in the flame reaction zone.Keywords: swirling flows, biomass pellets, combustion dynamics, mathematical model. IntroductionThe application of swirling flows for the design of combustion systems is important due to the swirl-induced formation of a toroidal recirculation zone, which results in enhanced mixing of a fuel with the air, in stabilization of combustion dynamics and in greater combustion efficiency. The comprehensive research of the confined swirling flows includes an experimental study and a numerical analysis of the development of the downstream flow structure and combustion dynamics by varying the flow geometry, boundary conditions and swirl intensity [1][2][3][4][5]. These studies have shown that relatively small variations of the inlet conditions and configuration of the swirl combustor can result in unpredictable variations of the flow patterns and main flame characteristics. Moreover, the complex research of the swirling non-reacting flow and flame dynamics in a cylindrical channel has revealed that the development of swirling flow patterns and flame structure correlate with the formation of downstream and upstream swirling air flows which are responsible for biomass gasification, mixing of the axial flow of volatiles with the air, ignition and combustion of volatiles and for the formation of main combustion characteristics [6]. Further research has shown that the formation of the downstream and upstream swirling flow patterns and swirling flame structure is highly sensitive to the variations ...

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The structure of turbulent stratified and premixed methane/air flames II: Swirling flows

Cited by 146 publications

References 41 publications

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

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

Large eddy simulation of unconfined turbulent swirling flow

Experimental and numerical study of the development of swirling flow and flame dynamics and combustion characteristics at biomass thermo-chemical conversion

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