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Combustor Model Simulation for Turbulent Mixing and Combustion Fundamentals

Explore the accurate analysis of velocity fields and turbulent mixing alongside chemical kinetics to define combustion processes. Utilize CFD software to simulate velocity and temperature distribution in a combustor, validating with available results. Learn more about NOx prediction and gas turbine combustor simulation through the presented combustion model. Progress through formulating Fluent simulation problems, mesh generation, solver selection, and simulation initiation. References include NOx modeling evaluations and Fluent tutorials.

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Combustor Model Simulation for Turbulent Mixing and Combustion Fundamentals

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

  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.

  3. As-Is…… • Combustor geometry : • Fuel : C3H8 i.e. Propane . • Oxidant : O2+N2i.e. Air O2- 21% , N2- 79 % • Basic requirement in formulation is to look for the Fluent Models available for combustion

  4. Basics : • One step global mechanism for Propane oxidation C3H8+ 5(CO2+3.76 N2)= 3CO2 + 4H20 + (5x3.76) N2 • Reaction Rate : A=4.836 e+09 ,E= 1.256 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

  5. Combustor & Meshing Exhaust Air Fuel Combustor Layout As the flow is axisymmetric 2D Quadrilateral Mesh is generated

  6. Fluent Formulation • Solver : • 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

  7. Fluent Formulation • Materials : • 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

  8. Fluent Formulation • Initialization : • Temperature : 1500 K • Solution Model : Solved for • Energy Equation • Turbulence • Reaction rates for elements • Iterations : • Convergence took 600 iterations.

  9. Results : Velocity contours • Two circulation zones • Central recirculation zone created by the fuel jet • Confined within annular recirculation zone by the air jet

  10. Results : Velocity radial spread

  11. Results : Temperature Contours • Follows the velocity contours • High temperature is formed along the axis

  12. Results : Temperature Axial spread • Rapid burning of fuel in very small section of the combustor.

  13. Results : Mass fraction Contours O2 N2 C3H8

  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.

  15. What Next ? • Simulation of Gas turbine combustor….

  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.

  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 483-91. • FLUENT Tutorials • Dr. Kirk , Class Notes .

  18. Thanking You ! Combustion Fundamentals Final Project presentation. Presented By :Sudhir Kulkarni Dec. 13, 2005.

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