˘ˇ ˆ - ieaghg 5_c/3_090910... · 2013. 7. 25. · ˇ ˆ ˙ full model (doosan babock,...
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Oliver Stein, Andreas Kempf
o.stein@imperial.ac.uk ; a.kempf@imperial.ac.uk
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• Background
• Inlet Conditions
• Geometric Modelling
• Turbulence Modelling
• Results: Non-Reacting / Coal Combustion
• Conclusions
• Future Work
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Thermal Input: 40MW
Fuel Versatility:
• Coal
• Heavy Fuel Oil
• Natural Gas
• Orimulsion
Facility Usage:
• New Burner Development
• Contract Burner Testing
• Third Party Burner Testing
• OxyCoal II
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Full Model (Doosan Babock, FLUENT/Gambit):
• CCTF & wind box (including coal inlet & SA/TA swirlers)�
• Mesh Type: Polyhedral, non-conformal interfaces
• 3.6M cells, local refinement to resolve geometry
• Boundary conditions: 3 inlets, 2x Overfire Air, 1 outlet
• Typical run parameters: 4 CPU cores, ~1 week (Coal)
• Limited control over SA/TA swirler mass fluxes
Compact Model (Imperial, StarCD/CCM+):
• CCTD w/o wind box, downstream of SA/TA swirlers
• Mesh Type: Polyhedral, conformal mesh
• 2.1M cells, local refinement where required
• Boundary conditions: 4 inlets, 2x Overfire Air, 1 outlet
• Inlet conditions derived from averages of Full Model
• Typical run parameters: 4-8 CPU cores, 3-7 days
• Nominal mass fluxes
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RANS Modelling Parameters:• Software: StarCD/CCM+
• Turbulence models:
• Standard k/eps (StarCD)
• Realisable k/eps (CCM+)�
• Order of convection terms:
• 1st Order (StarCD)
• 2nd Order (CCM+)�
• Thermal model: Enthalpy transport
• Solver: Steady State, SIMPLE
• Convergence: Residual Tolerance: 1x10-3 or
better, visual inspection, data comparison
• Grid: 2.1M cells, polyhedral
LES Modelling Parameters:• Software: In-house Code “PsiPhi”
• Turbulence model:
Smagorinsky Model
• Order of convection terms:
2nd Order
• Thermal model: Conserved Scalar Mixing
• Solver: Low Mach Predictor/Corrector
• Convergence: Statistical Averaging
• Grid: 45.4M cells, hexahedral + immersed BCs
(shorter furnace model)
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Radial Probe, z/D = 0.0
Radial Probe, z/D = 2.3
Radial Probe, z/D = 4.9
Radial Probe, z/D = 9.9
Axial Probe
• Vertical 2D YZ slice: Contours
• 4 Radial line probe locations (horizontal)�
• 1 Axial line probe (burner axis)�
LES Domain
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IC-CCM+ (RANS) vs. IC-StarCD (RANS) DB-Fluent (RANS) vs. IC-PsiPhi (LES)
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IC-CCM+ (RANS) vs. IC-StarCD (RANS) DB-Fluent (RANS) vs. IC-PsiPhi (LES)
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IC-CCM+ (RANS) vs. IC-StarCD (RANS) DB-Fluent (RANS) vs. IC-PsiPhi (LES)
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IC-CCM+ (RANS) vs. IC-StarCD (RANS) DB-Fluent (RANS) vs. IC-PsiPhi (LES)
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• Modelling of Coal Particle Transport:
• Injection of coal particles of measured size distribution into the primary air stream
• Lagrangian particle tracking until (near) complete combustion
• Modelling of Devolatilisation:
• Constant rate model: stable flame for start-up, low devolatilisation temperature
• Single step model: higher accuracy, realistic devolatilisation temperature
• Modelling of Char Combustion:
• 1st Order effect model (kinetic parameters from lab analysis)
• Modelling of Gas Phase Combustion:
• EBU based on 2-step combustion mechanism
• Modelling of Radiative Heat Transfer:
• Discrete Ordinate Method (DOM): Ordinate set S2+, participating media/particles/walls
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Constant Rate Devolatilisation: Temperature Contour, Effect of Radiation (DOM-S2)
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• Carried out non-reacting (RANS & LES) and reacting (RANS) calculations of Doosan Babcock’s CCTF.
• Non-reacting Simulations (Quantitative Comparisons):
• IC’s RANS results from StarCD and CCM+ for the nominal mass flow rates agree well.
• Lower turbulence levels in StarCD likely stem from the lower order of convective discretisation.
• IC’s LES results (first shot) are comparable to Doosan Babcock’s RANS FLUENT model.
• LES data additionally contains time-resolved turbulence information (flow dynamics, length/time scales,
Re stress, etc.)
• Reacting Simulations (Preliminary Qualitative Results):
• Constant rate devolatilisation (low Tdev) results in a long, hot flame stabilising near the flame holder.
•1st order devolatilisation results in a cooler flame stabilising near the burner quarl.
• Radiative heat transfer modelling using DOM with coarse S2 discretisation has a slight cooling effect.
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• Short Term:
• Continue coal combustion analysis & validate preliminary findings
• Study parameter sensitivity of coal combustion model
• Carry out quantitative comparisons (air firing)
• Compare CFD results to experimental data
• Perform realistic oxyfuel coal combustion simulations
• Mid to Long Term:
• Carry out detailed simulations of oxy-fuel firing and compare results to air firing
• Investigate the applicability of LES to coal combustion
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