Reacting Flow Applications in STAR-CCM+
Outline Various Applications Overview of available reacting flow models Latest additions Example Cases Summary
Reacting Flows Applications in STAR-CCM+ Ever-Expanding application coverage – Gas turbine, process heaters, burners, and furnaces • Partially-premixed combustion models • LES – Chemical Vapor Deposition • Detailed/Global Surface chemistry • multi-component diffusion – Aftertreatment (Automotive) • Detailed/Global Surface chemistry • Coupled with liquid film and porous media – Energy Industry (Coal and Biomass combustion) • Multiple Coal Types and gas-fuel in a single simulation
Reacting Flows Applications in STAR-CCM+ – Chemical Process Industry (liquid-liquid reactions) • Finite-rate chemistry model with a flexibility to modify EOS • EMP inter/intra-phase reactions • Moment methods • Surface Chemistry – Rocket Engines (Solid, Liquid, and Hybrid) • Particle Reactions in Lagrangian • Real – Gas model with all Combustion Models • Coupled Solver – High-speed jet engines (Ramjet, Scramjet) • Coupled solver with combustion models – Oil and Gas • Multiple-Phase reactions (intraphase and interphase)
Spray Physics for Liquid Fuels Primary and Secondary Break-up Turbulence Dispersion Mass Transfer Collisions/Coalescence Droplet-Wall Interactions & Fluid-Film Formation
Reacting Flow Models in STAR-CCM+ Non-Premixed Combustion – EBU • Standard, Hybrid, Finite-Rate • User Defined – PPDF (Multi-stream) • Equilibrium • Flamelet – PVM (Chemistry Table) Premixed Combustion – CFM (Choice for Laminar flame speed) – PEBU Partially-Premixed Combustion – PCFM • Equilibrium • Flamelet – EBU – PVM Finite-Rate Chemistry Calculation using DARS-CFD – EDC – ISAT – Dynamic Load Balancing Surface Reactions with and without DARS-CFD Soot and Nox Emission Models
Latest Additions (v 8.02/v 8.04) Surface Chemistry – Global mechanisms Combustion Models with Real Gases – SRK and Peng-Robinson EOS Soot Model – MBH Model – Soot absorption properties Eulerian Multi-phase Reaction Model – Flexibility to add user defined reactions Complex Chemistry Model (DARS-CFD) – ISAT Further enhancements and testing for LES – Dynamic Procedure
Surface Chemistry After-treatment devices: - Three-Way Catalytic Converters (TWC) - Diesel Oxidation Catalyst (DOC) - Diesel Particulate Filter (DPF) - Selective Catalytic Reduction (SCR) Challenges in After treatment Calculations - Complex Geometry of Channels - Conjugate Heat Transfer - Gas-Phase Chemistry - Surface Chemistry involving Catalyst - Transient Effects
Results – Uniformity Calculations Flow ow Direc ection ion is from om left to o righ ght • Solid id Cone ne Spray ray with h 70 o , not ot much h • turb urbule ulent nt disper persion ion Therm ermolysi olysis cons nsum umes Urea ea quit ite rapidl apidly • Conv nvers rsion ion Efficien iciency & U Unif iform rmity ity Index ndex of • NH3 and nd H2O O can n be deduc educed ed from rom this is analys alysis is. This is can n help lp opt ptimiz imize injecti jection n strat rateg egy for or • UWS upstream eam of SCR system em.
Detailed Chemistry with Porous Media
Two-Step SCR Model Kinetics Parameters
Built-in Surface Chemistry Model Surface chemistry interface manual setup User has an option of setting the surface species and components manual as well.
Results – NOx Reduction Comparison Two-Step Model Detailed Surface Chemistry
Real Fluid Modeling in STAR-CCM+ - Real Fluid Physics in STAR-CCM+ - Van der Waals - Redlich-Kwong (RK) - Peng-Robinson (PR) - Soave-Redlich-Kwong (SRK, available in 8.02) - Modified Soave-Redlich-Kwong (MSRK, available in 8.02) - All above Equation of Sates are Cubic
Real Fluid Thermodynamic Departures En Enthalpy halpy : Spec ecific ific Heat t : Entro ropy py : Speed ed of Sound nd :
Results (Compressibility Factor, Z) p = Z Z ρ RT, Z = = 1 for id ideal l gas PR PR SRK Depa parture ure from m Ideal al Gas beha havi vior or is is Sig Signific ifican ant !
Results (Density Comparison) PR PR SRK Ideal al Gas
Soot modeling Two-Equation Soot Model Transp nsport ort equation tions s are solve lved for two wo soot variab iables les – Soot number er densit ity y (N) N) and Soot t Mass s densit ity y (M) Key physical processes are : – Nucleation – Coagulation – Soot growth – Soot oxidation
Nucleation Acetylene PAH inception inception C 2 H 2 C 2 H 2 , , C 6 H 6 , , C 6 H 5 , , H 2 Current Co Compute ute fro rom: m: approach 1. Species ies li list 2. Empir irical ical (non- premix mixed) d)
“Soot Source Term” on “User Specified Processes” can n be user er-specified pecified fie ield ld functi tion ons
Two-eq equat uation ion model del with ithout ut radiat diation ion All t ll the scaling aling factors tors for sour urce e terms rms are e 1.0 Two-eq equat uation ion model del with ith radiat diation ion Mome ments nts model del with ith radiation diation
Compa mparis rison n of prof ofiles iles alo long ng the center nter lin line For r Two-equa quation ion model del radiat diation ion effec ects ts are e not cons onsidered idered
Centerline Temperature Comparison (EBU)
Centerline Temperature Comparison (Flamelet)
Centerline Soot Profile Comparison (EBU)
Centerline Soot Profile Comparison (Flamelet)
Inter-Phase Reactions with EMP Three reactions • Gas Oil -> Gasoline Gas Oil -> Coke Gas Oil -> Light Gases Reaction rates are in Arrhenius form • All reactions are second order Deactivation by the deposition of Coke on the catalyst surface is also included. 28
Inter-Phase Reactions with EMP Following Options are • Provided First-order combined rate • Half-order combined rate • Second-order combined • rate User reaction rate • 29
Gas phase reaction setup in STAR-CCM+ When using the built-in • reaction rate expression, input the temperature exponent • activation energy • pre-exponent, and • the diffusion coefficient. • 30
Gas phase reaction mechanism Three reactions • Gas Oil -> Gasoline Gas Oil -> Coke Gas Oil -> Light Gases Reaction rates are in Arrhenius form • All reactions are second order Deactivation by the deposition of Coke on the catalyst surface is also included. 31
Temperature of Catalyst and Gas Phase 32
Mass Fractions of Gas Oil and Gasoline 33
General Overview of Furnace Flow Fe 2 O 3 Ore e / Cok oke e Layer yer Fe 3 O 4 - Fall lls s down wn very y slowly. wly. FeO Fe Gas Gas Cohesive hesive Zone ne - Hot t gas s inje jecti ction - Flow w upwa ward rd throu rough ore / - Ore laye yer r tempera ratu ture re coke ke laye yers rs incr crease ses - Lost st of heat t into to ore / coke ke - Blocke cked gas s passa ssage due laye yers to melte ted ore - Chemica ical l react ctio ions s with th - Cohesive sive zone of larg rge ore / coke ke volu lume
Eulerian porous media approach Gas Phase • Three components: CO/CO2/N2 Porous media • Three components: Fe/Ore/Coke Boundary conditions: • Outlet boundary: Pressure outlet Inlet boundary: Mass fraction of the gas phase: CO/N2=0.8/0.2. Velocity = 15 m/s, Temperature = 2000K 35 35
Chemical reactions Two reactions • C + CO2 -> 2CO Fe2O3 + 3CO -> 2Fe + 3CO2 Time step: 1 sec The model is stable and fast: 32 processors, one hour, simulated around 3000 seconds in the physical time. 36 36
Coke and Ore particle area 37 37
Conversion of Ore into Fe 38 38
Eulerian multiphase: 2-phase model Full size furnace: • 25m height • 7.2m hearth diameter • 2D axisymmetric model • M ulti-component Eulerian phases: • Gas phase: CO, CO2, N2 Solid phase: Ore, Coke, Fe, Fe2O3, C Two reactions: • Fe2O3 + 3CO -> 2Fe + 3CO2 C + CO2 -> 2CO 39 39
Volume Fractions 40
Temperatures 41
Complex Chemistry • Can read Chemkin format and no limit on number of species • Online tabulation using ISAT is available – Factor of 2-5 speedup is commonly observed • Dynamic load balancing is available to achieve scalability for chemistry calculation with large number of processors. • DARS-Basic provides tool to reduce the chemistry that can be imported in STAR-CCM+ for further speedup for complex chemistry calculations.
High-Speed Jet Engines (Ramjet, Scramjet) Fuel: el: H2 at 134 K Oxid idize izer: r: H2O,O2,N O2,N2 at 1187 87 K Coupled upled solver lver PPDF Equilib uilibrium rium Compa mparis rison n of H2O Prof ofile ile with ith experim perimen en
Conclusions Eulerian Multi-Phase with Reactions LES effective but expensive Finite-rate kinetics – Library-based – Direct chemistry coupling Speedup – Load balancing – Clustering – ISAT
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