large eddy simulation of a coal flame ... moguel...large eddy simulation of a coal flame: estimation...

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

06/09/2016 © The University of Sheffield

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.


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


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


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


7MethodologygyExperimental methodology

. . . ∫∫

.

.

.

∫∫

Processed grayscale

image

Transient intensity of the

flame

Overall intensity calculation

Frequency spectrum

constructiong


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


Particle treatment Unsteady discrete phase modeldomain of the furnace.


Boundary conditionsOxygen

mass flow rate (kg/s)

Recycle ratio (%)

Oxygen concentration

(primary, mass %)


(secondary, mass %)


(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

( )



. . . ∫∫

.

.

.

∫∫

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


11ResultsPredicted mean temperature distribution

Predicted instantaneous temperature distribution


12Results

Numerical estimation Experimental estimation


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


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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large eddy simulation of a coal flame ... moguel...large eddy simulation of a coal flame: estimation...

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