Reacting Flow Applications in STAR-CCM+ Outline Various - - PowerPoint PPT Presentation

Reacting Flow Applications in STAR-CCM+

Various Applications Overview of available reacting flow models Latest additions Example Cases Summary

Outline

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+

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)

Primary and Secondary Break-up Turbulence Dispersion Mass Transfer Collisions/Coalescence Droplet-Wall Interactions & Fluid-Film Formation

Spray Physics for Liquid Fuels

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

Reacting Flow Models in STAR-CCM+

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
• w Direc

ection ion is from

• m left to
• righ

ght

• Solid

id Cone ne Spray ray with h 70o, not

• t much

h turb urbule ulent nt disper persion ion

• Therm

ermolysi

• lysis 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

• r

UWS upstream eam of SCR system em.

Detailed Chemistry with Porous Media

Two-Step SCR Model Kinetics Parameters

Surface chemistry interface

manual setup

User has an option of setting the surface species and components manual as well.

Built-in Surface Chemistry Model

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)

PR PR SRK p = Z Z ρRT, Z = = 1 for id ideal l gas Depa parture ure from m Ideal al Gas beha havi vior

• r is

is Sig Signific ifican ant !

Results (Density Comparison)

PR PR SRK Ideal al Gas

Soot modeling

Two-Equation Soot Model

Transp nsport

• rt 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 PAH inception Acetylene inception

C2H2, , C6H6, , C6H5, , H2 C2H2 Co Compute ute fro rom: m:

• 1. Species

ies li list

• 2. Empir

irical ical (non- premix mixed) d) Current approach

“Soot Source Term” on

“User Specified Processes” can n be user er-specified pecified fie ield ld functi tion

• ns

Two-eq equat uation ion model del with ithout ut radiat diation ion Mome ments nts model del with ith radiation diation Two-eq equat uation ion model del with ith radiat diation ion All t ll the scaling aling factors tors for sour urce e terms rms are e 1.0

Compa mparis rison n of prof

• files

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

• nsidered

idered

Centerline Temperature Comparison (EBU)

Centerline Temperature Comparison (Flamelet)

Centerline Soot Profile Comparison (EBU)

Centerline Soot Profile Comparison (Flamelet)

Inter-Phase Reactions with EMP

28

• 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.

Inter-Phase Reactions with EMP

29

• Following Options are

Provided

• First-order combined rate
• Half-order combined rate
• Second-order combined

rate

• User reaction rate

Gas phase reaction setup in STAR-CCM+

30

• When using the built-in

reaction rate expression, input

• the temperature exponent
• activation energy
• pre-exponent, and
• the diffusion coefficient.

Gas phase reaction mechanism

31

• 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.

Temperature of Catalyst and Gas Phase

32

Mass Fractions of Gas Oil and Gasoline

33

General Overview of Furnace Flow

Ore e / Cok

• ke

e Layer yer

• Fall

lls s down wn very y slowly. wly.

Gas Gas

• Hot

t gas s inje jecti ction

• Flow

w upwa ward rd throu rough ore / coke ke laye yers rs

• Lost

st of heat t into to ore / coke ke laye yers

• Chemica

ical l react ctio ions s with th

• re / coke

ke

Cohesive hesive Zone ne

• Ore laye

yer r tempera ratu ture re incr crease ses

• Blocke

cked gas s passa ssage due to melte ted ore

• Cohesive

sive zone of larg rge volu lume

Fe2O3 Fe3O4 FeO Fe

Eulerian porous media approach

35 35

• 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

Chemical reactions

36 36

• 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.

Coke and Ore particle area

37 37

Conversion of Ore into Fe

38 38

Eulerian multiphase: 2-phase model

39 39

• Full size furnace:
• 25m height
• 7.2m hearth diameter
• 2D axisymmetric model
• Multi-component Eulerian phases:

 Gas phase: CO, CO2, N2  Solid phase: Ore, Coke, Fe, Fe2O3, C

• Two reactions:

 Fe2O3 + 3CO -> 2Fe + 3CO2  C + CO2 -> 2CO

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

• file

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

45

LES

• Dynam

namic ic Proc

• cedure

dure

• All

ll Yplu lus treat eatmen ment

• Seco

cond nd order der im implic licit it tim ime diff ifferenc rencing ing

• Both CD and

d BCD

• Non-re

reflect lecting ing boundar undary condition ndition

• Synt

nthet hetic ic turbulen bulence ce for in inflo low BC BC

• Reac

acti ting ng Flo low

• Thick

icken ened ed Fla lame me Model del

• Alg

Algebr braic aic Va Variance riance and d SD SDR

Soot Material & Model Properties

User Specified Soot Material Properties: Soot Absorption Coefficient (New Addition) Soot Density (default value: 1800 kg/m3) Soot Molecular Weight (default value: 24 kg/kg-mol) Soot Molecular Diffusivity Soot Turbulent Schmidt Number

Soot Radiation

• Soot Model can now influence the DOM Radiation Model by contributing

to the Absorption Coefficient

• Soot Absorption Coefficient Property now appears under Soot Material
• There are three ways user can specify the soot absorption coefficient
• Constant
• Planck Mean Coefficient (built in)
• Field Function (User-Specified)

Planck’s Mean Coeff (Soot)

Ka_soot = 3.8322 (C0)(fv)(T)/C2

Where, C2 = 0.014388 m-K and C0 = 4.9 (constant that user can change)

References:

• Brooke and Moss, “Predictions of Soot &

Thermal Radiation properties in Confined Turbulent Jet Diffusion Flames, C&F, 1999

• Modeling soot formation in turbulent

kerosene/air jet diffusion flames, Wen et. al, C&F 2003

• Radiative Heat Transfer, Modest 2003

An Example Validation Case*

*Reference: “Temperature and Soot Volume Fraction in Turbulent Diffusion Flames: Measurements of Mean and Fluctuating Values,” A. Coppalle & D. Joyeux, Combustion & Flame, 96: pp 275-285, 1994

Geometry

Fuel Inlet Axis Overall Boundary Conditions:

• Fuel Inlet: 29.5 m/s @ 322 K
• Axis
• All other boundaries are Pressure Outlet

Pressure Outlet (Air) Velocity Inlet (C2H4) r = 2 mm

Close-Up View at Fuel Inlet

Axis

Physics Continuum Models

• Axis-Symmetric
• Steady
• k-w SST Turbulence Model
• Non-Premixed Combustion
• Flamelet Model* and EBU 1-Step Model (2 cases)
• DOM Radiation (WSGG Method)
• Soot Radiation with Planck’s Mean Coeff
• Soot Moments Model*

* Flamelet Table based on lumped PAH n-heptane mechanism (209 species). Flamelet

Library was generated using DARS-Basic with input conditions from the experimental

• study. The fuel stream was C2H4 and the oxidizer stream was Air.

EBU Results – Total Absorption Coeff Comparison

No Soot Radiation With Soot Radiation

Results – Temperature Comparison

No Soot Radiation (EBU) With Soot Radiation (EBU) With Soot Radiation (Flamelet)