Experimental investigation of isothermal scalar mixing fields downstream of axisymmetric baffles under fully premixed or stratified inlet mixture conditions

Paterakis, Georgios; Politi, E.; Koutmos, P.

doi:10.1016/j.expthermflusci.2019.05.018

Cited by 16 publications

(32 citation statements)

References 26 publications

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“…In Figure 3-2, the combustor-burner subsystem, which has been developed and manufactured at the in-house workshop (LAT), is illustrated. The combustion tunnel (Dc of 52mm diameter) envelopes the studied burner, which is similar to those reported in [46,47]. The LAT premixer/burner configuration consists of three axisymmetric baffles (A, B, C), forming two cavities, connected along their axis with a vertical hollow tube of 10mm diameter, Figure 3-3.…”

Section: Combustor-burner Subsystemsupporting

confidence: 67%

“…For the velocity field characterization, a two-dimensional particle image velocimetry (2DPIV, LaVision® FlowMaster 2D) was used, as illustrated in Figure 5-1 and reported in detail in [46].…”

Section: Pivmentioning

confidence: 99%

“…These concepts referred to the formation of mixture composition gradients before entrance to the combustion zone [45]. When the levels of mixture fraction extent beyond the flammability limits, the flame configuration is called "partially premixed", otherwise it is called "stratified" [45][46][47][48][49][50]. They are expected to improve flashback, instability, fuel consumption, emissions and combustion efficiency, as well as to extend operational range and fuel flexibility through a more effective control of the spatial mixture [45,[47][48][49][51][52][53][54].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, only fewer works have paid specific attention on the effect of the inlet mixture variations, between the stratified and the fully premixed settings, on flame front anchoring and stabilization, particularly under limiting operating conditions downstream of practical stabilizers [46,47,77].…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

Paterakis¹,

Πατεράκης²

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The current work describes an experimental investigation of isothermal and turbulent reacting flow field characteristics downstream of axisymmetric bluff body stabilizers under a variety of inlet mixture conditions. Fully premixed and stratified flames established downstream of this double cavity premixer/burner configuration were measured and assessed under lean and ultra-lean operating conditions. The aim of this thesis was to further comprehend the impact of stratifying the inlet fuelair mixture on the reacting wake characteristics for a range of practical stabilizers under a variety of inlet fuel-air settings. In the first part of this thesis, the isothermal mean and turbulent flow features downstream of a variety of axisymmetric baffles was initially examined. The effect of different shapes, (cone or disk), blockage ratios, (0.23 and 0.48), and rim thicknesses of these baffles was assessed. The variations of the recirculation zones, back flow velocity magnitude, annular jet ejection angles, wake development, entrainment efficiency, as well as several turbulent flow features were obtained, evaluated and appraised. Next, a comparative examination of the counterpart turbulent cold fuel-air mixing performance and characteristics of stratified against fully-premixed operation was performed for a wide range of baffle geometries and inlet mixture conditions. Scalar mixing and entrainment properties were investigated at the exit plane, at the bluff body annular shear layer, at the reattachment region and along the developing wake were investigated. These isothermal studies provided the necessary background information for clarifying the combustion properties and interpreting the trends in the counterpart turbulent reacting fields. Subsequently, for selected bluff bodies, flame structures and behavior for operation with a variety of reacting conditions were demonstrated. The effect of inlet fuel-air mixture settings, fuel type and bluff body geometry on wake development, flame shape, anchoring and structure, temperatures and combustion efficiencies, over lean and close to blow-off conditions, was presented and analyzed. For the obtained measurements infrared radiation, particle image velocimetry, laser doppler velocimetry, chemiluminescence imaging set-ups, together with Fouriertransform infrared spectroscopy, thermocouples and global emission analyzer instrumentation was employed. This helped to delineate a number of factors that affectcold flow fuel-air mixing, flame anchoring topologies, wake structure development and overall burner performance. The presented data will also significantly assist the validation of computational methodologies for combusting flows and the development of turbulence-chemistry interaction models.

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Section: Combustor-burner Subsystemsupporting

confidence: 67%

Section: Pivmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

Paterakis¹,

Πατεράκης²

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“…More recently, the experimental work investigated by [9] discussed the characteristics of isothermal flow and scalar mixing fields, downstream of a variety of axisymmetric baffles in a double-cavity disc burner configuration. The aim of this work was to enhance the knowledge of the effect of inlet fuel-air mixture conditions and the geometric parameters of blockage ratios in the near recirculating wake of the practical flame stabilizers.…”

Section: Introductionmentioning

confidence: 99%

Comparative Appraisal of Response Surface Methodology and Artificial Neural Network Method for Stabilized Turbulent Confined Jet Diffusion Flames Using Bluff-Body Burners

Gendy¹,

Ghoneim²,

Zakhary³

2020

WJET

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The present study was conducted to present the comparative modeling, predictive and generalization abilities of response surface methodology (RSM) and artificial neural network (ANN) for the thermal structure of stabilized confined jet diffusion flames in the presence of different geometries of bluff-body burners. Two stabilizer disc burners tapered at 30˚ and 60˚ and another frustum cone of 60˚/30˚ inclination angle were employed all having the same diameter of 80 (mm) acting as flame holders. The measured radial mean temperature profiles of the developed stabilized flames at different normalized axial distances () j x d were considered as the model example of the physical process. The RSM and ANN methods analyze the effect of the two operating parameters namely () r , the radial distance from the center line of the flame, and () j x d on the measured temperature of the flames, to find the predicted maximum temperature and the corresponding process variables. A three-layered Feed Forward Neural Network in conjugation with the hyperbolic tangent sigmoid (tansig) as transfer function and the optimized topology of 2:10:1 (input neurons: hidden neurons: output neurons) was developed. Also the ANN method has been employed to illustrate such effects in the three and two dimensions and shows the location of the predicted maximum temperature. The results indicated the superiority of ANN in the prediction capability as the ranges of R 2 and F Ratio are 0.868-0.947 and 231.7-864.1 for RSM method compared to 0.964-0.987 and 2878.8 7580.7 for ANN method beside lower values for error analysis terms.

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Effects of Stratification and Preheat on Turbulent Flame Characteristics and Stabilization

Souflas

Koutmos

2021

Flow Turbulence Combust

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Experimental investigation of isothermal scalar mixing fields downstream of axisymmetric baffles under fully premixed or stratified inlet mixture conditions

Cited by 16 publications

References 26 publications

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

Comparative Appraisal of Response Surface Methodology and Artificial Neural Network Method for Stabilized Turbulent Confined Jet Diffusion Flames Using Bluff-Body Burners

Effects of Stratification and Preheat on Turbulent Flame Characteristics and Stabilization

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