OpenFoam project at Politecnico di Milano

G. D’Errico

Dipartimento di EnergeticaPolitecnico di Milano

Some information:

•Politecnico di Milano is a public university.

•About 40.000 students in 2003/2004 (25.000 studentsin the Engineering Faculties, 4.000 students in the Design Faculty, 11.000 students in the ArchitectureFaculty).

•300 new PhD students per year.

•In 2004 Politecnico has 1.133 academics (396 full professors, 390 associate professors and 347 lecturers) and 870 administrative and technicalemployes.

•Graduated in engineering at Politecnico representabout 12,7% of all the graduated in engineering of Italy.

The Department of Energetics:(Dipartimento di Energetica)

Research and teaching in the following fields:

• Internal combustion engines• Powerplants and energy systems• Turbomachinery• Aerospace Propulsion• Thermodynamics• Acoustics

Internal combustion engine group (www.engines.polimi.it)Staff: Prof. Giancarlo FerrariProf. Angelo OnoratiDr. Gianluca D’Errico

Post-doc researchers: Gianluca Montenegro, Tarcisio Cerri, Federico Piscaglia

PhD students: Tommaso Lucchini, Marco Miglioli

MSc students (≈15-20 thesis per year)

Calculation of exhaust gas composition by means of multi-zone combustion models.

1D and 3D thermo-fluid dynamic modelingof S.I. engines (gasoline, natural gas, hydrogen)and C.I. engines (Diesel, HCCI) GASDYN, OpenFoam

Simulation of wave motion and chemical species transport, with reactions in the gas and solid phase in the exhaust ducts of a s.i. engine.Prediction of catalyst conversion efficiency and light-

off time during a warm-up.

Thermo-fluid dynamic modeling of i.c. engines

Silencers

Exhaust after-treatment system (3way CC, deNOx SCR, Diesel oxi-cat, DPF, etc.)

Air injection system

Intake system

Combustion

1D Thermo-fluid dynamic modeling of i.c. engines

Lamborghini 6.2 L V12 S.I. engine

Thermo-fluid dynamic simulation of the Lamborghini 6.2 L V12 S.I. engine.

Modeling of the intake system for the prediction of the volumetric efficiency, performances and emissions.

Companies, research centres and universities currently involved in the development and application

of the 1D GASDYN model:

• LAMBORGHINI• SEATEK• ELASIS• BMW• MVAGUSTA-CAGIVA• FAURECIA• LAFRANCONI SILENCERS• MIVV EXHAUST SYSTEMS• ART ENGENEERING• ISTITUTO MOTORI (CNR)• UNIVERSITY OF MODENA• POLITECNICO DI TORINO• UNIVERSITY OF ROME (Tor Vergata)• UNIVERSITY OF PERUGIA• UNIVERSITY OF PARMA• UNIVERSITY OF BOLOGNA

Companies, research centres and universities currently involved in the development and application

of the 1D GASDYN model:

• LAMBORGHINI• SEATEK• ELASIS• BMW• MVAGUSTA-CAGIVA• FAURECIA• LAFRANCONI SILENCERS• MIVV EXHAUST SYSTEMS• ART ENGENEERING• ISTITUTO MOTORI (CNR)• UNIVERSITY OF MODENA• POLITECNICO DI TORINO• UNIVERSITY OF ROME (Tor Vergata)• UNIVERSITY OF PERUGIA• UNIVERSITY OF PARMA• UNIVERSITY OF BOLOGNA

OpenFoam - GASDYN

MultiDMultiD Research topicsResearch topics

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

DEVELOPMENT: ENGINE MESHDEVELOPMENT: ENGINE MESH

FOUR STROKE ENGINES: FOUR STROKE ENGINES: Mesh motion MOVIE. Section of a 3D engine withMesh motion MOVIE. Section of a 3D engine withvertical valvesvertical valves

Layer addition/removalLayer addition/removalon the on the pistonpiston patchpatch

Layer Layer addition/removaladdition/removalon the on the valveTopvalveTop andandvalveBottomvalveBottom patchespatches

slidingInterfaceslidingInterfacecontinuoslycontinuoslyattached andattached anddetacheddetached

Switching Switching beetweenbeetweendeformation deformation and layeringand layering

MultiDMultiD Research topicsResearch topics

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

ChemicalChemical modelsmodels

Development of a reduced kinetic scheme for the evaluation of the main chemical species (particularly NO and CO) in premixed turbulent flame.

1D laminar flame

validationvalidation

QuasiQuasi--D and CFD D and CFD combustion in combustion in CNG enginesCNG engines

CFD CFD analysisanalysis of of methane and methane and

air steady air steady turbulent flameturbulent flame

SAE 2005-01-1123

ReducedReduced kinetickinetic schemescheme

To remove O-O2 equilibrium assumption

To characterize the kinetically controlled species

To assume partial equilibrium for the species whose reactions are much faster

To achieve a computational time efficiency

Paper # 2005-01-1123

Closure of the chemical systemClosure of the chemical system

The proposed chemical scheme considers:4 elements: O, N, C, H 11 chemical species: N2, H2O, CO2, CO, O2, H2, H,

O, OH, NO, HO2. NO, CO and H are computed kinetically, O, OH, H2 are in partial equilibriumHO2 is derived by the steady-state assumption.

The remaining species, N2, H2O, O2 and CO2 can be derived applying the element conservation

Paper # 2005-01-1123

CFD Combustion ModelCFD Combustion Model

The proposed chemical scheme was first embedded into the multidimensional code OpenFOAM

Weller combustion model

Solve the transport equations for mass, momentum, energy chemical species and turbulence properties, an equation representing the average position of the interface is solved

Paper # 2005-01-1123

CFD Combustion ModelCFD Combustion Model

The evolution of the combustion process is defined by the normalized fuel mass fraction:

( ) ( ) |~|~~~~bSbDbU

tb

uuu ∇Ξ−=∇∇−∇+∂∂ ρρρρ

The wrinkle factor can be derived by solving the following transport equation:

( ) ( ) Ξ⋅−+Ξ−−Ξ=Ξ∇+∂Ξ∂ )0,max(1 stRGUt

σσ)

Paper # 2005-01-1123

1D validation for Laminar Flow1D validation for Laminar Flow

Detailed chemical code, FlameMaster

A lean mixture of air and methane (Φ=0.8) is considered at atmospheric pressure with an initial unburned gas temperature equal to 400 K.

The chemical composition is evaluated in the post-flame zone and the proposed scheme is compared with the full kinetic scheme and with the standard approach

Paper # 2005-01-1123

1D validation for Laminar Flow1D validation for Laminar Flow

NO concentration profiles in a 1D laminar

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 0.002 0.004 0.006 0.008 0.01distance [mm]

mol

ar c

once

ntra

tion/

10-5

NO complex kinetics

NO proposed model

NO Zeld. + equilibrium

Paper # 2005-01-1123

1D validation for Laminar Flow1D validation for Laminar Flow

O concentration profiles in a 1D laminar

0.000

0.001

0.001

0.002

0.002

0.003

0.003

0.004

0 0.002 0.004 0.006 0.008 0.01distance [mm]

mol

ar c

once

ntra

tion

O complex kinetics

O proposed model

O equilibrium

Paper # 2005-01-1123

CFD validation for Turbulent FlowCFD validation for Turbulent Flow

Turbulent confined flame in a high velocity premixed flow of methane and air, ignited by a parallel flow of hot

Air is preheated up to 600 K, the inlet velocity is approximately 55 m/s and the equivalence ratio Φ=0.8. Coarse mesh of 9100 cells.

Paper # 2005-01-1123

CFD validation: velocity profilesCFD validation: velocity profiles

Ux ( x = 0.039 m )

0

0.02

0.04

0.06

0.08

0.1

0 30 60 90 120 150Axial velocity [m/s]

Wal

l dis

tanc

e [m

] EXPERIMENTALCALCULATED

Paper # 2005-01-1123

CFD validation: velocity profilesCFD validation: velocity profiles

Ux ( x = 0.250 m )

0

0.02

0.04

0.06

0.08

0.1

0 30 60 90 120 150 180Axial velocity [m/s]

Wal

l dis

tanc

e [m

] EXPERIMENTALCALCULATED

Paper # 2005-01-1123

CFD validation: velocity profilesCFD validation: velocity profiles

Ux ( x = 0.450 m )

0.00

0.02

0.04

0.06

0.08

0.10

0 30 60 90 120 150 180 210Axial velocity [m/s]

Wal

l dis

tanc

e [m

] EXPERIMENTALCALCULATED

Paper # 2005-01-1123

CFD validation: velocity profilesCFD validation: velocity profiles

Ux ( x = 0.650 m )

0

0.02

0.04

0.06

0.08

0.1

0 30 60 90 120 150 180 210 240Axial velocity [m/s]

Wal

l dis

tanc

e [m

]

EXPERIMENTALCALCULATED

Paper # 2005-01-1123

CFD validation: NO profilesCFD validation: NO profiles

NO ( x = 0.222 m )

0

0.02

0.04

0.06

0.08

0.1

0.E+00 1.E-05 2.E-05 3.E-05 4.E-05 5.E-05 6.E-05Molar fraction

Wal

l dis

tanc

e [m

]

Experimental

Proposed mechanism

Equilibrium + Zeldovich

Paper # 2005-01-1123

CFD validation: NO profilesCFD validation: NO profiles

NO ( x = 0.322 m )

0

0.02

0.04

0.06

0.08

0.1

0.E+00 1.E-05 2.E-05 3.E-05 4.E-05 5.E-05 6.E-05Molar fraction

Wal

l dis

tanc

e [m

]

Experimental

Proposem mechanism

Equilibrium + Zeldovich

Paper # 2005-01-1123

CFD validation: NO profilesCFD validation: NO profiles

NO ( x = 0.522 m )

0

0.02

0.04

0.06

0.08

0.1

0.E+00 1.E-05 2.E-05 3.E-05 4.E-05 5.E-05 6.E-05 7.E-05Molar fraction

Wal

l dis

tanc

e [m

]

Experimental

Proposed mechanism

Equilibrium + Zeldovich

Paper # 2005-01-1123

CFD validation: NO profilesCFD validation: NO profiles

NO ( x = 0.692 m )

0

0.02

0.04

0.06

0.08

0.1

0.E+00 1.E-05 2.E-05 3.E-05 4.E-05 5.E-05 6.E-05 7.E-05Molar fraction

Wal

l dis

tanc

e [m

]

Experimental

Proposed mechanism

Equilibrium + Zeldovich

Paper # 2005-01-1123

Engine simulationEngine simulation

Engine thermoEngine thermo--fluid dynamic modelfluid dynamic model

It is possible to predict: • engine performances• cylinder emissions

exhaust system warm-upcatalyst efficiencytailpipe emissionstailpipe noise

Integrated simulation (thermodynamic, fluid dynamic and chemical) of the whole engine system, considering pre-catalysts, catalysts and silencers (GASDYN)

Paper # 2005-01-1123

Paper # 2005-01-1123

Engine simulation: Fiat Engine simulation: Fiat LanciaLancia 2.0L VIS2.0L VIS

Fuelled with Gasoline and CNG

Engine simulation: Fiat Engine simulation: Fiat LanciaLancia 2.0L VIS2.0L VIS

Engine simulation: Fiat Engine simulation: Fiat LanciaLancia 2.0L VIS2.0L VIS

Engine simulation: Fiat Engine simulation: Fiat LanciaLancia 2.0L VIS2.0L VIS

Engine simulation: Fiat Engine simulation: Fiat LanciaLancia 2.0L VIS2.0L VIS

NonNon--equilibrium emission modelequilibrium emission model

MultiDMultiD Research topicsResearch topics

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

3D fluid dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

GDI SPRAY MODELLINGGDI SPRAY MODELLING

SPRAYSPRAY

LagrangianLagrangian descriptiondescription

Cell to Cell Tracking according to the mass,Cell to Cell Tracking according to the mass,momentum and energy exchange with the GAS momentum and energy exchange with the GAS ((EulerianEulerian) phase) phase

PARCELSPARCELS

ADDITIONAL MODELSADDITIONAL MODELS

ATOMIZATIONATOMIZATION: initial droplets size and spray angle: initial droplets size and spray angle

BREAKUPBREAKUP: droplets deformation due to the aerodynamic forces: droplets deformation due to the aerodynamic forces

EVAPORATIONEVAPORATION: energy exchange with the gas phase: energy exchange with the gas phase

COLLISIONCOLLISION: droplet/droplet interaction: droplet/droplet interaction

TommasoTommaso LucchiniLucchini Ph.D. thesisPh.D. thesis

GDI SPRAY EVOLUTIONGDI SPRAY EVOLUTION

PRESSUREPRESSURE--SWIRL SWIRL INJECTORINJECTOR

FUEL LIQUID SHEETFUEL LIQUID SHEET

PRIMARY BREAKUPPRIMARY BREAKUP

LIQUID SHEETLIQUID SHEETINSTABILITYINSTABILITY

LIGAMENTSLIGAMENTS

DROPLETSDROPLETS

SECONDARY BREAKUPSECONDARY BREAKUP

EVAPORATIONEVAPORATION

PRESSURE SWIRL INJECTORPRESSURE SWIRL INJECTOR

m&

x

z

αβ

αβ

x

z

INJECTOR DATAINJECTOR DATA

Diameter (Diameter (dd00))

Spray angle (Spray angle (αα))

Mass flow rate ( )Mass flow rate ( )

Injection pressure (Injection pressure (pp))

Initial Droplet Initial Droplet Velocity (Velocity (UU))

lv

pkUρ∆

=2

Initial Spray Initial Spray Angle (Angle (θθ))

βαθ ⋅−+= )1,1(2

rnd

Initial Sheet Initial Sheet Thickness (Thickness (hh))

)( hdUhm l −=πρ&

ATOMIZATION MODELATOMIZATION MODEL

LISA MODEL (LISA MODEL (Linear Instability Analysis of a Viscous Liquid Linear Instability Analysis of a Viscous Liquid SheedSheed))

AERODYNAMIC INSTABILITYAERODYNAMIC INSTABILITY WAVE GROWTHWAVE GROWTH

The growth rate (The growth rate (ωω) and the wave number () and the wave number (kk) are related) are related

fuelfuel

airfuelfuels

kkUkkρσ

ρρννω

322422 42 −++−=

ΩΩss, maximum growth rate is responsible for the , maximum growth rate is responsible for the breakupbreakup

⎟⎟⎠

⎞⎜⎜⎝

⎛Ω

=0

ln1ηητ b

S

BreakupBreakupTimeTime

τVL =

BreakupBreakupLengthLength

LigamentsLigamentsDiameterDiameter

sL K

hd 8= ( ) 6/13188.1 Ohdd LD +=

DropletsDropletsDiameterDiameter

hh, liquid sheet half, liquid sheet half--thickness calculated by mass conservationthickness calculated by mass conservation

SECONDARY BREAKUPSECONDARY BREAKUP

KHRT MODELKHRT MODEL

TWO DIFFERENT BREAKUP MECHANISMSTWO DIFFERENT BREAKUP MECHANISMS

KelvinKelvin--HelmoltzHelmoltz: : child parcels child parcels are stripped off are stripped off from the parent from the parent parcelparcel

RayleighRayleigh--Taylor: Taylor: catastrophic catastrophic breakupbreakup, much , much smaller droplets smaller droplets creationcreation

EVAPORATION MODELEVAPORATION MODEL

( ) gasdropletev pTp >

Droplet diameter reduction after the primary Droplet diameter reduction after the primary breakupbreakupInitial spray cone angle is increasedInitial spray cone angle is increased

FUEL HEATED BY THE INJECTORFUEL HEATED BY THE INJECTOR

DROPLET FLASH EVAPORATION (DROPLET FLASH EVAPORATION (TTdroplet,surfacedroplet,surface > > TTgasgas))

( )( )b

dropletboilingdropletsfd TL

ATTGm

−==α

&

( ) ⎥⎦⎤

⎢⎣

⎡ −⎟⎠⎞

⎜⎝⎛ ++

+= ∞

b

bf

fp TLhh

GG

GGNur

ckG 11ln

/12 0πGGm fd +=&

DROPLET SUPERHEAT EVAPORATION (DROPLET SUPERHEAT EVAPORATION (TTdroplet,surfacedroplet,surface < < TTgasgas))

SPRAY EVOLUTION IN THE SPRAY EVOLUTION IN THE OpenFoamOpenFoam CODECODE

MESHMESH((fvMeshfvMesh))

SPRAYSPRAY((sprayspray))

SPRAY FUNCTIONSSPRAY FUNCTIONS((spraySubModelsspraySubModels()()))

inject(), inject(), atomizationLoopatomizationLoop()()

breakupLoopbreakupLoop(), (), evaporate(), evaporate(),

collide()collide()

………………

VALIDATIONVALIDATION

--INFLUENCE OF INJECTION PRESSUREINFLUENCE OF INJECTION PRESSURE

--DROP SIZE PREDICTIONDROP SIZE PREDICTION

--INFLUENCE OF AMBIENT PRESSUREINFLUENCE OF AMBIENT PRESSURE

--INFLUENCE OF FUEL TEMPERATUREINFLUENCE OF FUEL TEMPERATURE

INFLUENCE OF INJECTION PRESSUREINFLUENCE OF INJECTION PRESSURE

DROP SIZE PREDICTIONDROP SIZE PREDICTION

R

Z

DROP SIZE PREDICTIONDROP SIZE PREDICTION

Z=7.5

R=3

DROP SIZE PREDICTIONDROP SIZE PREDICTION

Z=10

R=2

Z=10

R=3

INFLUENCE OF AMBIENT PRESSUREINFLUENCE OF AMBIENT PRESSURE

AMBIENTAMBIENT PRESSURE 1 barPRESSURE 1 bar

t = 0.5 mst = 0.5 ms t = 1.0 mst = 1.0 ms t = 1.5 mst = 1.5 ms

t = 2.0 mst = 2.0 ms t = 2.5 mst = 2.5 ms t = 3.0 mst = 3.0 ms

INFLUENCE OF AMBIENT PRESSUREINFLUENCE OF AMBIENT PRESSURE

INFLUENCE OF FUEL TEMPERATUREINFLUENCE OF FUEL TEMPERATURE

INFLUENCE OF FUEL TEMPERATUREINFLUENCE OF FUEL TEMPERATURE

T = 375 K (T = 375 K (∆∆TTSHSH = 0 K)= 0 K)

T = 405 K (T = 405 K (∆∆TTSHSH = 30 K)= 30 K)

MultiDMultiD Research topicsResearch topics

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

Intake and Exhaust Fluid Dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

Mesh modifiers with topological change

Combustion modeling with reduced kinetic schemes

Spray modeling (GDI, Diesel, HCCI)

Intake and Exhaust Fluid Dynamics:steady flows of complex devices1D-3D couplingSilencer modeling

Noise analysis

Expansion chamber

Noise analysis

0

2

4

6

8

10

12

14

0 100 200 300 400 500 600 700 800 900 1000

frequenza [Hz]

TL [d

B]

Teoria classica FoamHz 6122

00 ==

La

f

Computed and theoretical transmission loss

Noise analysis

Column resonator

Noise analysis

-5

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500 3000

frequenza [Hz]

TL [d

B]

Teoria classica Foam

Computed and theoretical transmission loss

Noise analysis

Helmholtz

resonator

-5

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000 2500 3000

frequenza [Hz]

TL [d

B]

Teoria classica Foam

Computed and theoretical transmission loss

Noise analysis

Hz 6122

0 0 ==

La

f alelongitudin Hz 9272

0 0 ==

ha

f etrasversal

Expansion chamber with non-axial inlet-outlet

0

5

10

15

20

25

30

35

40

45

0 500 1000 1500 2000 2500 3000

frequenza [Hz]

TL [d

B]

Gasdyn FoamHz 612 0 =alelongitudinf

Hz 927 0 =etrasversalf

Politecnico di Milano – Dipartimento di Energetica

Expansion chamber at 860 Hz

1D-3D coupling

Same solver (HLLC Riemann solver) is usedin the two domains

OpenFoam: 1D-3D couplingOpenFoam: 1D-3D coupling

Future projectsFuture projects

4 stroke engine with lateral valves

Design and optimization of a new Diesel engine

HCCI modeling

Any idea ???

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