Transcript Dia 1 - UGent

Ghent University-UGent
Department of Flow, Heat and Combustion Mechanics
Analysis of pre-tabulated chemistry models in flame simulations
R. De Meester1, B. Naud2, U. Maas3, B. Merci1
University – UGent, Dept. of Flow, Heat and Combustion Mechanics, Ghent, Belgium
2Modeling and Numerical Simulation Group, Energy Dept., Ciemat, Madrid, Spain
3Institute for Technical Thermodynamics, Karlsruhe University (TH), Germany
1Ghent
Table: 1D↔2D
Tabulated Chemistry Models
• Reduce detailed chemical mechanisms to lower dimensional table
Temperature
Production of CO2
• Parameterization:
 Mixture
 Mass
fraction Z: mixing of fuel and oxidizer
1D table
fraction Y(CO2): progress of reaction
2D table
• Effect of diffusion on the chemistry included through spatial gradients
obtained from laminar diffusion flame calculations
Test Case
Numerical Framework
• Swirling Bluff Body Flame
• Fuel Jet: CH4
1D: r   P ( Z ).r ( Z ).dZ
2D: r   P( Z , YCO2 ).r ( Z , YCO2 ).dZ .dYCO2
Mean Density
Mean Viscosity
Swirling Annulus: Air
Coflow: Air
• Bluff Body: creates recirculation zone
• Highly rotating collar: region of high shear
→separates 2 recirculation zones + local extinction
FLOW FIELD
COMPOSITION
RANS
Finite Volume
Scalar PDF
Monte Carlo
Chemistry
table
1D: Z
2D: Z + Y(CO2)
Mean Velocities
Mean Turbulent properties
• Stoichiometric mixture fraction: 0.054
Flame Structure in Physical Space
Tangential Velocity
Mixture Fraction
Mass Fraction of CO2
Mass Fraction of OH
Flame Index
Premixed flame:
→ reaction
Diffusion flame:
→ mixing
+
reaction
• 1D↔2D: ≠ flow field
≠ T, r and composition fields
≠ flame structure
Flame Structure in Composition Space
Experiment
Calculation
Monte Carlo
Connection between physical and composition space
Evolution of computational particles
REACTION
REACTION
PREMIXED
FLAME
MIXING
MIXING
MIXING
REACTION
REACTION
MIXING +
REACTION
DIFFUSION
FLAME
MIXING
• 1D: only Z independent parameter
forced diffusion flame structure of 1D table
• 2D: extra independent parameter Y(CO2)
diffusion and premixed flame structures
MIXING
Conclusions
• The progress variable in the 2D table
possible to describe mixing of 2 gases at any point of reaction progress
• 1D table ↔ 2D table : forced diffusion flame structure ↔ diffusion and premixed flame structures
• Work in progress: extension to tabulated chemistry for spray combustion