A comparison of the characteristics of disk stabilized lean propane flames operated under premixed or stratified inlet mixture conditions

Karagiannaki, Ch.; Dogkas, E.; Paterakis, Georgios; Souflas, Konstantinos; Psarakis, Emmanouil Ζ.; Vasiliou, P.; Koutmos, P.

doi:10.1016/j.expthermflusci.2014.04.002

Cited by 23 publications

(31 citation statements)

References 19 publications

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“…The combustion tunnel and the burner geometry described below in detail are similar to those reported also in [3,13] and a schematic layout of the experimental setup is provided in Figure 1. The premixer/burner system was composed of three concentric axisymmetric disks connected along their axis with a vertical hollow tube, namely, a forebody disk (C), a hollow fuel injecting disk (B in Figure 1), and the flame stabilizing afterbody (A) (D b =0.025 m).…”

Section: Experimental Setup and Methodsmentioning

confidence: 70%

“…The flow variables, F, were expressed as resolvablẽand subgrid, , level quantities using a Favreweighted filter,̃= / . The resolved scale flow quantities are described by the following equations [10,13,15,16]: continuity is…”

Section: Numerical Models and Solution Proceduresmentioning

confidence: 99%

“…Specifically, image acquisition and data reduction were performed using the Davis 8.05 software (LaVision5). The background images, taken under the same integration time and gain as the flame images, were then subtracted from the originals similar to [13]. For phaseaveraged imaging, the CCD camera was synchronized with the inlet pressure signal and 100 instantaneous images, at a maximum interrogation window (1626 × 1236 pixels), were taken repeatedly at predetermined phase-angles (0 ∘ , 90 ∘ , 180 ∘ , and 270 ∘ ); =0 ∘ corresponds to the negative-to-positive reference signal transition and =90…”

Section: Measurement Techniques Pressure Transducers and Hotmentioning

confidence: 99%

“…The signal-to-noise ratio of the instantaneous images was better than 5:1 and the exposure time was 2.1 ms. Moreover, intensifier gate times of the order of 100 s were used for the measurements with a gain at 75%, analogous to [13].…”

Section: Measurement Techniques Pressure Transducers and Hotmentioning

confidence: 99%

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Effect of Modulation of the Inlet Velocity and Equivalence Ratio Gradients on the Stabilization of Stratified Axisymmetric Bluff-Body Flames

Paterakis

Koutmos

2018

Journal of Combustion

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An investigation of ultralean stratified, disk stabilized, propane flames operated with acoustic modulation of the inlet velocity and fuel-air mixture profiles is presented. Transverse acoustic forcing was applied to the air, upstream of a double-cavity premixer section, formed along three concentric disks, which fueled the stabilization region with a radial mixture gradient. Measurements and supporting Large Eddy Simulations with a nine-step mechanism for propane combustion were performed to evaluate variations in the ultralean flame characteristics under forced and unforced conditions. The effects of forcing on the heat release profiles and on the interaction of the toroidal flame with the recirculation region are examined and discussed. The impact of the acoustic excitation of inlet conditions on the local extinction behavior is, also, assessed by monitoring a local stability criterion and by analyzing phase-resolved chemiluminescence images.

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Section: Experimental Setup and Methodsmentioning

confidence: 70%

Section: Numerical Models and Solution Proceduresmentioning

confidence: 99%

Section: Measurement Techniques Pressure Transducers and Hotmentioning

confidence: 99%

Section: Measurement Techniques Pressure Transducers and Hotmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Modulation of the Inlet Velocity and Equivalence Ratio Gradients on the Stabilization of Stratified Axisymmetric Bluff-Body Flames

Paterakis

Koutmos

2018

Journal of Combustion

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“…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%

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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Effects of Stratification and Preheat on Turbulent Flame Characteristics and Stabilization

Souflas

Koutmos

2021

Flow Turbulence Combust

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A comparison of the characteristics of disk stabilized lean propane flames operated under premixed or stratified inlet mixture conditions

Cited by 23 publications

References 19 publications

Effect of Modulation of the Inlet Velocity and Equivalence Ratio Gradients on the Stabilization of Stratified Axisymmetric Bluff-Body Flames

Effect of Modulation of the Inlet Velocity and Equivalence Ratio Gradients on the Stabilization of Stratified Axisymmetric Bluff-Body Flames

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

Effects of Stratification and Preheat on Turbulent Flame Characteristics and Stabilization

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