1. Combustor Model Simulation
Combustion Fundamentals
Final Project presentation.
Presented By :Sudhir Kulkarni
Dec. 13, 2005.
11/17/2018

2. Motivation
Accurate analysis of velocity field represents flow characteristics & turbulent mixing properties ,when coupled with chemical kinetics defines combustion process which represents temperature distribution in flow.
To utilize CFD software FLUENT coupling turbulence mechanism with chemical kinetics to simulate velocity and temperature distribution in a combustor.
Check the simulation output with the available results.
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3. As-Is…… Combustor geometry : Fuel : C3H8 i.e. Propane .
Oxidant : O2+N2 i.e. Air
O2- 21% , N2- 79 %
Basic requirement in formulation is to look for the Fluent Models available for combustion
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4. Basics : R C3H8=A exp(-E/RT) [C3H8]0.1 [O2]1.65 Ữt = ρCỮ k2/ε
One step global mechanism for Propane oxidation
C3H8+ 5(CO N2)= 3CO2 + 4H20 + (5x3.76) N2
Reaction Rate :
A=4.836 e+09 ,E= e+08
Arrhenius Law, Boltzman Constant, Rate Factors
Turbulent Viscosity:
R C3H8=A exp(-E/RT) [C3H8]0.1 [O2]1.65
Ữt = ρCỮ k2/ε
k: Turbulent Kinetic energy
ε : Dissipation rate
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5. Combustor & Meshing Combustor Layout
Air
Exhaust
Fuel
Combustor Layout
As the flow is axisymmetric 2D Quadrilateral Mesh is generated
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6. Fluent Formulation Solver : Viscous Model : Species Model
Steady state , Axisymmetric, Segregated
Viscous Model :
K-Epsilon Model : RNG model Opted for simulation
Reynolds Stress equation
Species Model
Species Transport : Being General , Opted for simulation .
Premixed
Non-Premixed
Partially Premixed
Turbulence and chemistry interactions
Eddy-dissipation/Finite rate : Opted for simulation
Eddy dissipation
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7. Fluent Formulation Materials : Boundary conditions :
Propane –air Mixture :
To utilize the mixture properties from fluent database
Heat capacities of individual fluid are set for temperature dependent polynomial considering the temperature variation in the zone.
Boundary conditions :
Air-Inlet :- Axial Component of velocity : 0.75
-Radial component of velocity : 0.25
[ To match with the geometry of the combustor ]
- Turbulent specification :
Intensity & hydraulic diameter : Opted for simulation
Intensity & length scale
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8. Fluent Formulation Initialization : Solution Model : Solved for
Temperature : 1500 K
Solution Model : Solved for
Energy Equation
Turbulence
Reaction rates for elements
Iterations :
Convergence took 600 iterations.
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9. Results : Velocity contours
Two circulation zones
Central recirculation zone created by the fuel jet
Confined within annular recirculation zone by the air jet
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10. Results : Velocity radial spread
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11. Results : Temperature Contours
Follows the velocity contours
High temperature is formed along the axis
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12. Results : Temperature Axial spread
Rapid burning of fuel in very small section of the combustor.
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13. Results : Mass fraction Contours
C3H8
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14. What Next ? Prediction Of NOx
NOx concentration depends mainly on the temperature distribution and hence on the turbulence as well.
Formulation of This combustion model with velocity and temperature can be well utilised for NOx evaluation.
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15. What Next ?
Simulation of Gas turbine combustor….
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16. Learning's……
Formulating the combustion problem for the Fluent simulation.
Preparation of geometry and mesh formation in Gambit (in consideration with the fluent facilities)
Set the combustion problem in Fluent .Initiate and solve the simulation.
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17. References ……
Lei-Yong Jiang and Ian Campbell .”A critical evaluation of NOx modeling in a model combustor”. J. Engineering for gas turbine and power July 2005 Vol 127 P
FLUENT Tutorials
Dr. Kirk , Class Notes .
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18. Thanking You ! Combustion Fundamentals Final Project presentation.
Presented By :Sudhir Kulkarni
Dec. 13, 2005.
11/17/2018