Reacting cting Flow Modeling ling in n STAR-CC -CCM+ Rajesh sh - - PowerPoint PPT Presentation

Reacting cting Flow Modeling ling in n STAR-CC

• CCM+

Rajesh sh Rawat at

Latest est Addit itions ions (v 7.02/v v 7.04)

Eulerian ian Multi-phase phase Reacti ction

• n Model

el Soot

• t Model

el

– Moment Methods

PPDF Flamel elet – Multi-stream model Comple plex x Chemi mistr stry Model (DARS ARS-CFD) CFD) – EDC (additional modifications) – Dynamic Load Balancing – ISAT Further her enhancem ncemen ents ts and testi ting ng for LES Best st Practi tices ces for LES Misc

– Non-transported Passive Scalars – Permeable fixed flux or fixed species Boundary Conditions

Lagrangian rangian Multi tiphas phase e Capabilit bilites es

Par Particle cle radiation iation Mul ulti-co component ponent drop

• ple

let t evapora porati tion

• n

Genera neral l Par Particle cle Reacti tions

• ns

eros

• sion

ion mode dels Inject jector

• r Model

dels

– Part, Point, Hollow Cone and Surface Injectors

Primar ary y Atomi mizati zation

• n Model

del

– Pressure Swirl Injector (Lisa model)

Secondar condary Break akup Model del

– KHRT – Reitz-Diwakar – TAB

Inner er Angle le Outer er Angle le Orig igin in Axis is

Par Particle ticle React action ion Mo Model el

Par Particle cle Reacti ction

• n Model

del is available ble through

• ugh Lagrangi

rangian an Mul ultiphase phase frame mewor

• rk of STAR

AR-CC CCM+ M+ Two

• Reacti

ction

• n Models

dels are available: ble: Par Particle cle Devolatil atiliza izati tion

• n and Par

Particle cle Comb mbusti ustion

• n

Can simulat ate

– Particle Devolatilization, Sublimation, Melting – Particle Combustion, Oxidation, Pyrolysis

Particle Combustion

In partic icle le combustion mbustion modeli

• deling,

ng, a solid d particle cle reacts ts with th a gas-pha phase se species cies to form rm solid id and/or /or gas-phase phase produc ducts ts Three ree different rent meth ethod

• ds

s are available ble for speci cify fying ing the e react ction ion rates: es:

– First Order Combined Rate – Half Order Combined Rate – User-Defined Rate

The e combine mbined d rate consid nsiders gas-speci pecies es diffusi fusion

• n to the

e particl icle.

• e. The

e Diffusion usion Coef efficient cient can be speci cified ied by the us user as scalar ar profile. le.

Example Reactions

Par Particle cle Devolati tiliza izati tion

• n Model

del

• - CaCO3  CaO + CO2

Par Particle cle Comb

• mbusti

ustion

• n Model

del

• - 2Ca (s) + O2 (g)

(g)  2CaO (s)

• - NaOH (s) + HF (g)  NaF

F (s) + H2O (g)

• - Fe

Fe2O3 (s) + 3H2 (g) (g)  2Fe e (s) + 3H2O O

7

LES

• 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-reflec

reflecting ing bounda undary y condit ndition ion

• 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

lgebraic braic Varian riance ce and d SDR

Sandia dia D Flame ame

Mesh count: 4.1 M Polyhedrals in the vicinity of inlet Extruded Polyhedrals elsewhere Volumetric control in the flame region Approximately 0.18 mm of mesh size in radial direction

Temperat perature ure – Insta tantan ntaneou eous s & Mean

Movie e - Temperatu perature re

Comparis parison

• n with

th Exp xperi erimen ment t – C Cent nterl erlin ine e Axial ial Veloc

• city

ity

RMS Axia ial l Vel Mean an Axia ial l Vel

Compari parison

• n with

th Exp xperi eriment ment – Cent nterl erlin ine e Mixt xture ure Fr

LES S Best st Prac actices tices

Librar rary Based ed Models ls

STAR-CCM+

Transport Equations

H298 Source Term Premixed Flame (CFM)

Properties

Emissions source terms (Nox/soot)

PVM/Flamelet Library

The progress gress varia iable ble model el

15

• A precomputed table is used to store the effects of detailed

chemistry on combustion: selected species, source term to chemical enthalpy, mixture NASA polynomials, and molecular weight

• The combustion state is described using a progress variable

based on chemical enthalpy

• h298 is the chemical enthalpy for the mixture, while

h298|c= 0 and h298|c= 1 are the chemical enthalpies at the initial conditions and equilibrium state, respectively.

Premix emixed ed Gas Turbine bine

PVM DARS-CFD with GRI-Mech

Temperat perature ure Compar arison ison

Soot Model Validation

Centerline Temperature Profile

Centerline Soot Profile

Radial Profiles for Soot (x = 0.347)

Soot Distributions

Multi ti-Stream tream PPD PDF

Temperat perature ure & Lagrangian rangian Trac acking king

Comple plex x Chemistr emistry

• Can read

ad Chemk emkin in format rmat and no limit t on num umber ber of species cies

• Online

ne tabulati tion

• n us

using g ISAT is available ble

– Factor of 2-5 speedup is commonly observed

• Dynami

amic c load d balanc ncing ing is available ble to achieve scalabil bilit ity y for r chemis emistr try y calcula ulati tion

• n with

h large e num umbe ber r of process cessor

• rs.

s.

• DAR

ARS-Ba Basi sic c provide ides s tool

• l to reduc

duce e the e chemis emistr try y that t can be imp mpor

• rted

d in STAR AR-CC CCM+ M+ for fur urth ther er speedup eedup for comple plex chemis emistr try y calcula ulati tion

• ns.

s.

Dy Dyna nami mic Load Balancing ancing

20 40 60 80 100 120 140 Dynamic balancing Time (hours) Transient run

Transient run with load balancing

8p 16p 32p

Same non-premi premixed ed flame me but with more det etailed ailed mechanism hanism with h 53 speci ecies es tested ed for transient sient run Presen ented: ed: compl mplex x chemi mistr stry CPU time after 200 iterati tion

• ns

130 Hrs 60 Hrs 25 Hrs

The EDC model el

27

• The total space is divided into two zones
• Fine structures

 All the chemical reactions takes place  Represents the smallest turbulence scales

• Bulk structure

 No reactions occur

• The sub-grid chemistry scales don't need to be resolved at a

cell level.

Fine e stru ructures ctures

28

• Governing equations for the species and enthalpy
• * : quantities in the fine structure
• < > : the cell mean values.
• The residence time: how long the species remain in the fine

structures

• Mass fraction of fine structures in the cell:

Temperature Profiles

CH4 Profiles

SCR SCR

• 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 turbule urbulent nt disper persion ion

• Therm

ermolysi

• lysis

s 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.

Resu sults lts – NOx Reduct uction n Compari parison

• n

Two-Step Model Detailed Surface Chemistry

Conclusions lusions

Euler eria ian Multi-Phas Phase e wit ith Rea eacti tions

• ns

LES ef effec ecti tive e but expe pensiv ive Fi Finit ite-rate e kin inet etic ics

– Library-based – Direct chemistry coupling

Spe peed edup up

– Load balancing – Clustering – ISAT