LARGE EDDY SIMULATION OF A COAL FLAME: ESTIMATION OF THE FLICKER
FREQUENCY UNDER AIR AND OXY-QFUEL CONDITIONS
Presenter: Oscar Farias Moguel
Co-authors: Clements, A.G.a, Szuhánszki, J.a, Ingham, D.B.a, Ma, L.a, H i M M b L G b Y Y b P k h i M aHossain, M.M.b, Lu, G.b, Yan, Y.b, Pourkashanian, M.a
a Energy 2050, Faculty of Engineering,The University of Sheffield, Sheffield, UK, S10 2JT
b Instrumentation, Control and Embedded Systems Group, School of Engineering and Digital Arts,b Instrumentation, Control and Embedded Systems Group, School of Engineering and Digital Arts, The University of Kent, Canterbury, UK, CT2 7NT
2Contents
• Introduction
Obj i• Objectives
• Overview of the experimental facilities• Overview of the experimental facilities
• Methodology
• Results
C l i d f th k• Conclusions and further work
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3IntroductionOxy-fuel combustion
Mitigate GHG
Combustion Computational Efficiency/Limits/
Stability
Flow, temperature
pFluid Dynamics
(CFD)temperature,
species concentrations
Image 1. Representation of a retrofitted oxy-fuel combustion power plant.
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4Objectivesj
• Evaluate the oscillatory nature of the flame by LES simulationso Instantaneous values of temperature distribution
o Image and data processingg p g
• Obtain a trend for the flame dynamics under different oxy fuel conditionsdifferent oxy-fuel conditionso Air
Oo Oxy – 21, 25, 30
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5Overview of the experimental facilitiesexperimental facilities
Image 5. Different solid fuel particles used at PACT facilities .Image 4. Cross-section view of the
solid fuel burner installed at PACT facilities.
UKCCSRC Pilot-scale Advanced Capture Technology (PACT)
Location: South Yorkshire UKLocation: South Yorkshire, UK. Power output: 250 kWthGeometry: Down-fired furnace, refractory lined cylindrical shape, which is 4 m in height with a 0.9 cy d ca s ape, c s e g t t a 0.9m internal diameterBurner: Scaled version of a commercially available Doosan Babcock third generation low-NOx burnerImage 2 and 3. Picture and CAD representation of the 250
kW do n fired f rnace at PACT facilities
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gkWth down-fired furnace at PACT facilities.
6MethodologygyExperimental methodology
Video sectioning and frame recovery
Original videoCamera arrayIndustrial CMOS RGB camera:• 1280×1024 at 25 fps• 320 × 256 at 265 fps
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7MethodologygyExperimental methodology
. . . ∫∫
.
.
.
∫∫
Processed grayscale
image
Transient intensity of the
flame
Overall intensity calculation
Frequency spectrum
constructiong
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8MethodologygyNumerical methodology
CFD approachSoftware : ANSYS Fluent v15.0
3D mesh : Roughly 4 million hexahedrons
Fuel : ‘El Cerrejon’ (high volatile bituminous coal)
Turbulence Incompressible LES (WALE subgrid scaleTurbulencemodelling :
Incompressible LES (WALE subgrid scale model, Werner-Wengle wall functions)
Turbulence –Chemistry Eddy dissipation modelChemistryinteraction
Eddy dissipation model
RadiationWeighted sum of gray gases, full spectrum
correlated K modelco e ated ode
Devolatilisationmodel
Single rate
VolatileVolatile combustion
Two-step global reaction
Char combustion Intrinsic modelImage 6. CAD representation and computational
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Particle treatment Unsteady discrete phase modeldomain of the furnace.
9MethodologygyNumerical methodology
Boundary conditionsOxygen
mass flow rate (kg/s)
Recycle ratio (%)
Oxygen concentration
(primary, mass %)
Oxygen concentration
(secondary, mass %)
Oxygen concentration
(tertiary, mass %)
AIR 2.24×10-2 - 23.2 23.2 23.2
OXY21 2.15×10-2 77 19.0 19.0 19.0
OXY25 2.11×10-2 73 19.0 23.6 23.6
OXY30 2.08×10-2 67 19.0 23.6 29.5
Thermal input : 250 kW hThermal input : 250 kWth
SECONDARY (T=560K)PRIMARY (T=353K)
TERTIARY (T=560K)
central axis
( )
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10MethodologygyNumerical methodology
. . . ∫∫
.
.
.
∫∫
Grayscale contour of
temperature
Transient intensity of the
flame
Overall intensity calculation
Frequency spectrum
constructionp
Monitor points, lines and volumes were used in this study
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11ResultsPredicted mean temperature distribution
Predicted instantaneous temperature distribution
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13Conclusions and further workfurther work
ConclusionsConclusions• LES instantaneous results were successfully used to characterize
the flame
• Oxy-fuel flames showed lower flicker frequencies in comparison to the air-fired case
• Obtained a trend for the flame dynamics under different oxy-fuel conditions
F the o kFurther work• Evaluation of the turbulent coherent structures development in the
furnace and their impact on the flame oscillationfurnace and their impact on the flame oscillation
• Assessment of flame stability for different fuels
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14
AcknowledgementsThe authors would like to acknowledge EPSRC for funding this work Dr Sandy Black from DoosanThe authors would like to acknowledge EPSRC for funding this work, Dr. Sandy Black from Doosan Babcock Ltd. and the Mexican Council for Science and Technology (CONACyT) for the scholarship granted.
References1. Williams, et al. Co-firing Coal/Biomass and the Estimation of Burnout and NOx Formation.
BCURA Agreement Number B 79BCURA Agreement Number B 79.
2. Sun et al. An Embedded Imaging and Signal Processing System for Flame Stability Monitoring and Characterisation. 2010 IEEE International Conference on Imaging Systems and Techniques.
3. Huang et al. On-line flicker measurement of gaseous flames by image processing and spectral g g y g p g panalysis. Meas. Sci. Technol. 10 (1999) 726–733.
4. Johansson et al. Account for variations in the H2O to CO2 molar ratio when modelling gaseous radiative heat transfer with the weighted-sum-of-grey-gases model. Combustion and flame vol. 158 Issue 5 893 901158, Issue 5, 893–901.
5. Clements, et al. LES and RANS of air and oxy-coal combustion in a pilot-scale facility: Predictions of radiative heat transfer. Fuel vol. 151 , 146-155.
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