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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.
2
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
5
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)
6
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
7
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
8
Internal flow: sharp (spray C) vs. smooth (spray D) pressure decrease
Spray C Spray D
9
Without cavitation, Spray D produces a slightly longer liquid core length and a narrower cone angle
Spray C
Spray D
10
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:*
11
[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
17
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?
20
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
21
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
22
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
23
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
24
Contributions to T = Texit-Tinlet
•Expansion through the orifice
•Viscous energy dissipation
•Heat transfer through injector’s wall T
25
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]
26
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]
27
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
28
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]
29
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:
30
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
31
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
32
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
33
The measured Rate of Injection (ROI) and Rate of Momentum (ROM) of Spray A
Diagram from SAE 2013-24-0001
34
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]
41
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
42
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
44
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