evaluation of global reaction mechanisms for cfd modelling
TRANSCRIPT
3rd Oxyfuel Combustion Conference, Ponferrada, Spain, 2013
Evaluation of Global Reaction Mechanisms Evaluation of Global Reaction Mechanisms
for CFD Modelling of Oxy-Fuel Combustion
Fredrik Normann
Chalmers University of TechnologyChalmers University of Technology
BackgroundBackground
Purpose To obtain information for development of commercial oxy-fuel boilers
Progress of work Chalmers 100 kW oxy-fuel unitProgress of work Chalmers 100 kW oxy fuel unitOxy-CFB combustionSeries of experimental and modelling studies
Content of work Combustion issuesEmissions (NOx and SOx)Heat transferHeat transfer
Present presentation Evaluation of reduced reaction mechanisms for CH oxidation in CFD simulations
Fredrik Normann
Computational Fluid DynamicsComputational Fluid Dynamics
Complex GeometriesComplex GeometriesComplex Turbulent Flames
Simplified reaction mechanisms
Limited generalizability
Source: www.hightech.fiApplicability to oxy-fuel combustion with
high CO2 concentration?
Fredrik Normann
Global Reaction MechanismsAir Oxy-fuel
JL 3-step 4-step 6-step
Global Reaction Mechanisms
x x x x
x x xFuelOxidation
x x x x
x x xIntermediatesOxidation
x
x
Oxidation
Radicalx
Jones & Lindstedt, Leiser et al
2007Glarborg
et al 2009Frassoldatiet al 2009
Radical Formation
1988 2007 et al, 2009 et al 2009
Fredrik Normann
Mixing (turbulence)
Temperature (heat transfer)(heat transfer)
GeometryBoundary ConditionsValidation
Reaction Mechanism
Burner and Boiler Optimization
Fredrik Normann
Temperature MeasurementsTemperature Measurements
• Contour map created entirely from measurement data
• Six measurement positions
• Temperature and Concentration Profiles
Fredrik Normann
3D CFD Model• Sub-models:
k-ε Realizable turbulence d l
3D CFD Model
modelEddy Dissipation ConceptDiscrete Ordinates model with a WSGG model forwith a WSGG model for oxy-fuel conditions (grey)
• Flame shapeFlame shapeJL predicts a wider and shorter flame than the oxy-fuel derived mechanisms
• Concentration of COJL and 3-step yield the
di ti hi h tpredictions which are most in line with measured data
Generation of 1D-ModelGeneration of 1D Model
• Traced a “particle” from the fuel inlet throughout the furnace
• Recorded O2 concentration and temperature
Fredrik Normann
Comparison – CO concentration • The propane-fired Chalmers
100 kW OF27 flame
Comparison CO concentration
• Includes comparison with a detailed scheme
• Path-line data from CFD calculations is used in the PFR model
TemperatureO2 concentration
• Large discrepancies between the global models.
Comparison - Reaction Dynamics Fuel Oxidation CO Oxidation
Comparison Reaction Dynamics
Fredrik Normann
ConclusionConclusion
• There is a significant improvement potential for global oxy fuel• There is a significant improvement potential for global oxy-fuel reaction mechanisms and, thus, a need to develop a refined global reaction mechanism.
• Simply adjusting the reaction parameters to compensate for quantitative errors (such as over-predicted CO concentration or
b ti t t ) l d t i th ti d icombustion temperature) may lead to errors in the reaction dynamics
• A qualitatively incorrect behavior reduces the generic nature and li bilit f th h iapplicability of the mechanism.
Fredrik Normann
3rd Oxyfuel Combustion Conference, Ponferrada, Spain, 2013
Evaluation of Global Reaction Mechanisms Evaluation of Global Reaction Mechanisms
for CFD Modelling of Oxy-Fuel Combustion
Fredrik Normann
Chalmers University of TechnologyChalmers University of Technologyhttp://www.chalmers.se/en/projects/Pages/forbrannings
--och-koldioxidinfangningstekniker.aspx