Topic 1 – Internal flow Presenter: Marco Arienti, Sandia National Laboratories Support by Sandia...

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

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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

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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

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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)

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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

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Spray C: noticeable differences in boundary thickness between simulations

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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

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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.

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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

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Mass flow rate during opening transient*

*After removing all injection delays

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Momentum flow rate during opening transient

37

Jet penetration during opening transient

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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

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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

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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