Overview of Turbulent Reacting Flows

Overview of Turbulent Reacting Flows

Outline Various Applications Overview of available reacting flow models LES 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 High-speed jet engines (Ramjet, Scramjet) Coupled solver with combustion models Chemical Vapor Deposition Detailed/Global Surface chemistry multi-component diffusion Aftertreatment (Automotive) Detailed/Global Surface chemistry

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 EBU Combustion Energy Industry (Coal and Biomass combustion) Multiple Coal Types and gas-fuel in a single simulation 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 PPDF Equilibrium Flamelet Premixed Combustion CFM (Choice for Laminar flame speed) PEBU Partially-Premixed Combustion PCFM Equilibrium Flamelet EBU Surface Reactions with and without DARS-CFD

Reacting Flow Models in STAR-CCM+ Non-Premixed Combustion EBU Complex Chemistry PPDF PVM TFM Standard EBU Hybrid EBU Combined Time Scale EBU Kinetics Only EBU Operator Splitting Solves for Complex Chemistry using DARS-CFD Model. Turbulence-chemistry Interactions using Eddy Dissipation (EDC). Adiabatic /Non-Adiabatic Equilibrium Infinitely fast chemistry. Heat loss can be considered for non-adiabatic version Adiabatic /Non-Adiabatic Flamelet Used when non-equilibrium and scalar dissipation rate effects are important Look-up table generated using DARS steady Flamelets. PVM Model Along with Mixture Faction, a progress variable (chemical enthalpy) shows the progress of combustion. DARS constant pressure reactor used to generate look-up table based on initial conditions and detailed chemistry. TFM Model Used only with LES. Increases flame thickness by using a flame thickening factor. Computationally less intensive way of incorporating realistic chemistry.

Reacting Flow Models in STAR-CCM+ Premixed Combustion PEBU Complex Chemistry CFM TFM Fuel mass fraction tracked on the grid. Species mass fractions obtained using 1-step global scheme. Used when detailed chemistry description is desired. Solves ODEs and is computationally intensive. Flame area density and fuel mass fraction tracked on the grid. Uses 1 step global reaction scheme. Different flame speed models available: Guilder method, Metghalchi method, or User Defined Used in 3-D LES calculations for gas turbine combustors. Preferred with premixed combustion. Typical choice of flow model is segregated.

Reacting Flow Models in STAR-CCM+ Partially-Premixed Combustion EBU Homogeneous Reactor PCFM PVM TFM Standard EBU Hybrid EBU Combined Time Scale EBU Kinetics Only EBU Operator Splitting Solves for Complex Chemistry using DARS- CFD. Turbulence-chemistry Interactions can be accounted using Eddy Dissipation (EDC). Adiabatic /Non-Adiabatic Premixed combustion process handled with Coherent Flame Model, Non-premixed combustion process simulated using PPDF. Both Equilibrium and Flamelet models available for PPDF. PVM Model Along with Mixture Faction, a progress variable (chemical enthalpy) shows the progress of combustion. DARS constant pressure reactor used to generate look-up table based on initial conditions and detailed chemistry. TFM Model Used only with LES. Increases flame thickness by using a flame thickening factor.

Emission Models in STAR-CCM+ Emissions Model Soot - Flamelet based model. - Uses method of moments to calculate particle size distribution function. NOx Models NOx transport equation. Thermal NOx 4different models available based on 3- step extended Zeldovich mechanism. - Basic Zeldovich model - PPDF Equilibrium - PPDF Flamelet - Flamelet library Prompt NOx Needed under fuel rich conditions and in low temperature regions. Fuel NOx Used for fuels with nitrogen content. Can be used for a gaseous fuel, or liquid/coal in the Lagrangian phases. CO CO transport equation solved with PVM Combustion Model

Perspective view (endwall open) into furnace Mesh size is 35 Million cells 02/01/12 adapco Report 531-0015-001 Page 11

Burner installed geometry Tile Tertiary (premixed) gas tips Gas tips drilled per Zeeco GA 02/01/12 adapco Report 531-0015-001 Page 12

Temperature shown in two planes in the furnace 02/01/12 adapco Report 531-0015-001 Page 13

Temperature Contours at 6 intervals: Open end perspective view Note: Movies play in presentation mode (SHIFT-F5) 02/01/12 adapco Report 531-0015-001 Page 14

Tube Heat Fluxes (Btu/hr/ft2) This is the left coils (relative to Page 11) viewed from the flame side Tube 10, upper coil Tube 10, lower coil 02/01/12 adapco Report 531-0015-001 Page 15

Heater Geometry: Elevation View Looking East Convection Section Arch Tubes Outlet Tubes Radiant Tubes Radiant Inlet Tubes Air Inflow 09/20/11 Center Wall

09/20/11 adapco Report 1167- Page 17 Temperature Contours (vertical planes through center of burners 1 and 5 from East Wall) West

LES Algebraic and Dynamic Models Second order implicit time differencing Both CD and Bounded CD Non-reflecting boundary condition Synthetic turbulence for inflow BC Reacting Flow - Thickened Flame Model - Algebraic approach for Mix Fr Variance 18

Sandia-D Flame LES Simulation in STAR-CCM+ Mesh count: 4.1 M Polyhedrals in the vicinity of inlet Extruded Polyhedral elsewhere Full 360 o Pilot (1880 K) Fuel (CH4, 300 K)

Animation - Temperature

Comparison with Experiment Centerline Axial Velocity RMS Axial Vel Mean Axial Vel

Comparison with Experiment Centerline Mixture Fr RMS Mix Fr Mean Mix Fr

LES (Bluff Body - Vortex Shedding) Alternate Vortex Shedding Cold Flow Symmetric Vortex Shedding Reacting Flow

Pool Fire with LES T=1.5 sec T=2 sec T=2.5 sec T=3 sec T=3.5 sec T=4 sec

Partially-Premixed Gas-Turbine Combustion PVM DARS-CFD with GRI-Mechanism

Temperature Comparison PVM DARS-CFD with GRI-Mechanism

Latest Additions in Reacting Flows (v 7.06+) Advanced Emissions Modeling Soot Model with Moment Methods (up to 4 moments) CO emissions with PVM model PPDF Flamelet/Equilibrium Multi-stream (up to three streams) model Complex Chemistry Model (DARS-CFD) Dynamic Load Balancing ISAT Further enhancements and Best Practices for LES Detailed/Global Surface Chemistry within STAR-CCM+ Eulerian Multi-Phase reactions (interphase and intraphase) Real Gases with EBU Combustion Models (v8.02)

Soot Model Features - The Soot Model is based on Moments Method & uses Flamelet Library. - It can be used with all Combustion Models available in STAR-CCM+ - Up to four Moments can be solved - Soot source terms take into account the phenomena of particle inception, surface growth, fragmentation, oxidation, condensation & coagulation Soot Moment Model Calculates: - Soot Volume Fraction - Soot Mass - Soot Mean Diameter - Soot Surface Density - Soot Size Dispersion

Soot Model Validation Centerline Soot Profile

Soot Model Validation Radial Profiles for Soot (x = 0.347)

Multi-Stream (three) PPDF Approach

Inter-phase reactions in Eulerian Multi-Phase For each reaction reaction rate option as Half-order combined rate First-order combined rate Second-order combined rate User reaction rate 32

Complex Chemistry using DARS-CFD Complex Chemistry Model Features (DARS-CFD) Dynamic Load Balancing ISAT Online tabulation using ISAT is available Factor of ~5 speedup is commonly observed

Speed up with Dynamic Load Balancing Total solver CPU time no load balancing Time (sec) with load balancing Number of CPUs Dynamic load balancing achieves scalability for chemistry calculation with large number of processors

Time(s) Speed up with ISAT (82 Reactions, Unsteady) Total Complex Chemistry CPU time 25000 20000 15000 NO_ISAT 10000 ISAT 5000 0 1 Algorithm

Conclusions Comprehensive Set of Reacting flow models LES Looks Promising Finite-rate kinetics Library-based (PPDF Flamelet, PVM) Direct complex chemistry coupling (DARS-CFD) Global Kinetics (EBU) Speedup with Complex Chemistry Load balancing ISAT Advanced Emissions Models (NOx, Soot, CO)

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