Topic 1 – Internal flow

Presenter: Marco Arienti, Sandia National Laboratories

Support by Sandia National Laboratories’ LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National

Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin

Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

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Spray C/D (4 contributors)

•Politecnico di Milano - OpenFoam: Ehsanallah Tahmasebi, Tommaso Lucchini and Gianluca D'Errico

•ANSYS-FLUENT: Saeed Jahangirian, Aleksandra Egelja-Maruszewski, and Huiying Li

•Università di Perugia - Converge:Michele Battistoni

•CMT - CavitatingFoam (OpenFoam)Pedro Martí

3

Spray C Spray D

Common rail fuel injector Bosch 3-22

Fuel injector nominal diameter 0.20 mm

Nozzle K factor K=0

Nozzle shaping 5% hydroerosion

Flow with 10 MPa pressure drop 200 cc/min

Number of holes 1 (single hole)

Common rail fuel injector Bosch 3-22

Fuel injector nominal diameter 0.186 mm

Nozzle K factor K=1.5

Nozzle shaping Hydroerosion to Cd=0.86

Flow with 10 MPa pressure drop 228 cc/min

Number of holes 1 (single hole)

Axial coordinate

Radius

Wireframe of the tangentially-averaged interior wall of the sac

4

Institution/Code Uni-PGConverge

ANSYS-FLUENT

PolimiOpenFOAM -cavitatingFoam

CMT OpenFOAM -cavitatingFoam

Cavitation Model Homogenous Relaxation

Zwart-Gerber-Belamri

Homogenous Equilibrium

Inclusion of turbulent viscous energy generation

Y Y Y

TurbulenceLES Dynamic sgs

RANS:SST k-ωwith compress.

RANS:SST k-ω

RANS:- k-epsilon- SST k-ω

Spatial discretization 2nd order- QUICK for void fraction - 2nd order

2nd order 2nd order

Solver PISO Steady-State Coupled PIMPLE

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Uni-PGConverge

ANSYS-FLUENT PolimiOpenFOAM -cavitatingFoam

CMT OpenFOAM -cavitatingFoam

[1] Salvador et al., Mathematical and Computer Modelling 52 2010

[1] Desantes et al., SAE l Paper 2014-01-1418

[2] Khasanshin, et al. Int. J. of Thermophysics 24(5) 2003

[1] Caudwell et al., Int. J. of Thermophysics 25(5) 2004

[2] To match Khasanshin, et al. Int. J. of Thermoph. 24(5) 2003

[3] Zwart et al. ICMF 2004

EOS models

Schmidt et al., Int. J. of Multiphase Flow (2010)

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InstitutionCode

Uni-PGConverge

ANSYS-FLUENT

PolimiOpenFOAM

CMT OpenFOAM

Inlet boundary P = 150 MPa T = 343 K

Outlet boundary P = 20 MPa T = 303 K

Fixed fully open needle configuration

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InstitutionCode

Uni-PGConverge

ANSYS-FLUENT

PolimiOpenFOAM -cavitatingFoam

CMT OpenFOAM -cavitatingFoam

Dimensionality3D, full axis-

symmetric model 2D axis-

symmetric3D

5o wedge2D axis-

symmetric

Cell Type

- Cartesian cut cells- Wall functions, y+ = 30

Hex mesh with 10 boundary layers (from 1 μm)

Hex & tets quads

Cell count (total interior and exterior) 2.5 m 20k (79k in

adapted mesh)51k (Spray C) 54k (Spray D)

Submerged N Y Y Y

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Internal flow: sharp (spray C) vs. smooth (spray D) pressure decrease

Spray C Spray D

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Without cavitation, Spray D produces a slightly longer liquid core length and a narrower cone angle

Spray C

Spray D

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This effect is recognized in new measurements of the spray width and length

*from Fredrik Westlye’s presentation

From spray boundary contrast (threshold 0.37 KL) using the diffuse backlit illumination (DBI) technique:*

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[g/s]

• CONVERGE and FLUENT-ANSYS simulations are the only that capture the increase between spray C and D

• In the aggregate, there is more variation amongst models for the same spray type than between the sprays for the same model

Comparison against measured mass flow rate

12

Comparison against measured momentum

[N]

• CONVERGE and FLUENT-ANSYS simulations are the only to capture the increase between spray C and D (by a rather small margin)

13

SPRAY CExperimen

t(*)Uni-PG

ConvergeANSYS-FLUENT

PolimiOpenFOAM k-ω SST

CMT OpenFOAM

k-ε

CMT OpenFOAM k-ω SST

Mass flow rate (g/s)

10.07±0.11 10.3 10.8 12.8 10.3 10.4

Momentum (N)

5.83±0.06 6.29 6.49 7.69 6.30 6.79

SPRAY DExperimen

tUni-PG

ConvergeANSYS-FLUENT

PolimiOpenFOAM k-ω SST

CMT OpenFOAM

k-ε

CMT OpenFOAM k-ω SST

Mass flow rate (g/s)

11.72±0.15 10.9 11.3 11.6 10.2 10.5

Momentum (N)

7.03±0.11 6.41 6.62 6.27 6.24 6.69

Mass flow rate and momentum values

(*) std. dev. from the CMT measurements on 5 different specimens

14

Spray C: noticeable differences in boundary thickness between simulations

15

Spray CSpray CSpray DSpray D

Spray D vs. spray C at the exit orifice

• Similar velocity/density profiles are obtained for spray D• Cavitation displaces mass flow toward the orifice axis in spray C

16

The effect of cavitation for spray C• Note the different models’ effectiveness in generating

cavitation at the orifice’s wall liquid core boundary

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Conclusions• Relatively small variations in the amount of cavitation at the

wall result in differences of mass flow rate and momentum for spray C simulations• Even when the variation is correctly predicted, its magnitude is

underestimated

• The trend in spray penetration/width from spray C to spray D is correctly captured by the only non-submerged simulation (UniPG with Converge)• Cannot quantify agreement for lack of averaged data

• Passing pockets of vapor in the liquid core are shown in the only LES simulation (UniPG with Converge)• A frequency analysis of this feature is recommended

Topic 1.2 – Spray A needle transient opening

Presenter: Marco Arienti, Sandia National Laboratories

Support by Sandia National Laboratories’ LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National

Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin

Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

19

Two of the remaining questions for Spray A from ECN3:

1.What is the exit temperature of the fuel?

2.Is the injection transient modeled realistically?

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Spray A (3 contributors)

•CMT - OpenFOAM w/ Eulerian Spray AtomizationPedro Martí

• Bosch - Cascade Technologies Edward Knudsen, Eric Doran (Bosch Research & Technology Center)

•SNL - CLSVOFMarco Arienti

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Institution:Code:

BoschCascade Technologies

CMT OpenFOAMESA

SNLCLSVOF

Equation of State for the liquid phase Peng-Robinson

Non-linear (P,T)(Payri et al., Fuel 2011)

Tait eqn. calibrated for n-dodecane; new e(P,T)

Moving mesh N N/Y (axial only) Y

InletStatic pressure increases from 0.5Pinj to Pinj at t = 0

Time-varying static pressure Constant pressure

Turbulence LES Dynamic sgs model

RANSSST k-ω No turbulence model

Inclusion of turbulent viscous energy generation? Y Y N

Spatial Discretization 2nd order 1srorder 1st / 2nd order

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Spray A ANL SNL

Liquid T [K] 363 333 343

Gas 0% O2 N2 N2

Gas T [K] 900 303 440

Back-pressure [MPa] 6 2 3

Density kg/m3 22.8 22.8 22.8

Bosch*, CMT+ SNL+

At SNL and ANL, ambient density is matched at cooler, non-vaporizing conditions. From Lyle et al. SAE 2014-01-1412

*Tfuel,intern.< 363 K+Tfuel,intern. = 343 K

Spray A reference and actual laboratory conditions

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Exit temperature predictions from ECN3

T < 0T << 0T << 0T = 0

ANLConverge

SandiaCLSVOF

UMassHRMFoam

CMTESA

IFPC3D

Incompressible Non-linear function of p,T

Const. compressibility

Non-linear function of p,T

Stiffened gas EOS

turbulent viscous energy generation

turbulent viscous energy generation

T [K]

T ≅ 0

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Contributions to T = Texit-Tinlet

•Expansion through the orifice

•Viscous energy dissipation

•Heat transfer through injector’s wall T

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Peng-Robinson Calibrated Tait

100% C12H26

Tc = 658 K c =226 kg/m3

p = 2000 bar

= 0(T ), p0 = 1 bar

Liquid phase compression

[Caudwell et al., Int. J. of Thermophysics, 2004]

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p = -1440 bar T = -22 K from calibrated Tait EOS T = 0 K from isobaric EOS T = -217 K from adiabatic p.g. EOS ( =1.4)

Isentropic expansionupper bound:

787 kg/m3

363 K 1500 bar646 kg/m3

341 K60 bar

adiabatic p.g.: = 1.4

Density[ kg/m3]

Tem

pera

ture

[K]

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Adiabatic w.Adiabatic w.

SNL results show limited temperature increasewith adiabatic walls

TL,exit = +3 K TL,exit = +18 K L,exit = 716 kg/m3 L,exit = 720 kg/m3

343 351 359 367 375 383

Temperature [K]

720 736 752 768 784 800

Density [kg/m3]Constant TW = 383 K Constant TW = 383 K

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CMT results also show small T except near the wall

Adiabatic343 K

Constant TW = 363 K

Adiabatic343 K

ConstantTW = 363 K

Temperature [K] Density [kg/m3]

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The viscous dissipation of turbulent energy is the main source of temperature increase

273 K 303 K 323 K

343 K 363 KAdiabatic

Orifice cross-sections:

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However, the opening transient displays a bulk temperature increase

• Interpretation: the fuel heats up while passing through the narrow gap between needle and injector

Simulation with moving needleTw = 383 K

• This effect disappears once the passage is fully open

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Independent study: transient and non-isothermal modeling of cavitation with GFS*

*By Salemi, McDavid, Koukouvinis, Gavaises, and Marengo, in ILASS 2015

350 K

500 K

Minimum gap: 5 m(with standard wallfunction)

Minimum cell sizex = 0.5-0.83 m

Variation of the outlet temperature in one injection cycle

Steady-state temperature field

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Conclusions on T = Texit-Tinlet

1.Expansion through the orifice:• Moderate but constant during injection• Potentially under-estimated depending on EOS

2.Viscous energy dissipation:• Potentially large but transient• Puts under scrutiny the choice of standard wall

function in micron-size gap

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The measured Rate of Injection (ROI) and Rate of Momentum (ROM) of Spray A

Diagram from SAE 2013-24-0001

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Vgas = 0.065 mm3 (1/3of the sac)Tdelay = (339-330)s = 9 s

Tdelay = 3 s (instantaneous opening)Vgas = 4 m3 (half orifice)At t < 0 the pressure in the sac is ~Pinj/2

Fully open fuel passage

Time of apparent injection

Initial conditions: injection delay as a function of partially filled sac/orifice

35

Mass flow rate during opening transient*

*After removing all injection delays

36

Momentum flow rate during opening transient

37

Jet penetration during opening transient

38

T = 353 K

Pressure [MPa]

Spee

d of

sou

nd [m

/s]

• Example: speed of sound calculation for liquid n-dodecane1. Khasanshin et al., Int. J. of Thermophysics, 24(5) 20032. Padilla-Victoria, Fluid Phase Eq. 2013

3.

A request: establish a common set of properties and reliable EOS correlations

39

Backup

40

++

++

Temperature [K]

Inte

rnal

Ener

gy[k

J/kg

]

300 400 500 600 700-600

-400

-200

0

200

400

600

P = 0.1 MPaP = 20 MPaP = 140 MPa

New fit:

NIST data:P = 0.1 MPaP = 20 MPaP = 140 MPaSupercriticalSupercritical

Note 3: Dependence of internal energy on pressure

[JSAE 20159137 SAE 2015-01-1853]

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Experiment set-up and reference parametersFuel n-dodecane

Inlet pressure 150 MPa

Ambient pressure 6 MPa

Fuel Temperature 363 K

Vapor sound speed (m/s) 134.59

Liquid sound speed (m/s) 1037.8

Liquid saturation density (kg/m3) 697.13

Vapor density (kg/m3) 0.071548

Saturation pressure (Pa) 12622

Liquid viscosity (Pa.s) 5.6 e-4

Vapor viscosity (Pa.s) 5.44 e-6

Thermodynamic properties from NIST web-book (for dodecane):

Cav 0.042

Re 26k/32k

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Details of mesh preparation

43

MeshingNew meshing tool by Bosch-Cascade •Start from CAD surfaces•Seed domain with points•Build Voronoi diagram, connectivity

• No sliver cells at boundaries• Face normals point to cell centers• Minimal cell skew• More ‘sampling’ than hexes

Flow Domain

Voronoi Mesh

Chamber: 45 mm Long

Institution Bosch

Dimensionality 3

Cell Type 14-faced polyhedra

Cell count (total) 3x106

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Institution CMT

Dimensionality 2

Cell Type Quad

Cell count (total) 67.4K

Geometry 12x6 mm

Institution SNL

Dimensionality 3

Cell Type Cube

Cell count (total) 7x107 to 21x107

Geometry 1.7x1.7x15.3 mm