42
Contents • Extensive new capabilities available in STAR-CD/es-ice
v4.20
Combustion Models – see Marc Zellat presentation
Spray Models
LES
• New Physics Developments in v4.22
Combustion Models – PVM-MF
Crank-angle resolved Conjugate Heat Transfer
• New Meshing Technologies
Morphing/remeshing/mapping
Overset Mesh
Combustion – PVM-MF
• The PVM-MF model has been enhanced particularly for dual-
fuel combustion
• An example is shown here of diesel/gas combustion based
on the Westport combustion system
Picture source: http://www.westport.com/is/core-technologies/combustion
PVM-MF Dual-Fuel Combustion
• Engine Details
– Bore 130
– Stroke 150
– Conrod 260
– Compression ratio 18
• Operating Condition
– Engine speed 1500 rev/min
– AFR-NG 30.3, AFR-Diesel 273
– EGR 2.5%
– Fuel injection
• SOI Diesel 707oCA, Duration 3o
• SOI Gas 711oCA, duration 16o
Cylinder pressure and temperature
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
0.0E+00
2.0E+06
4.0E+06
6.0E+06
8.0E+06
1.0E+07
1.2E+07
1.4E+07
1.6E+07
1.8E+07
2.0E+07
600 630 660 690 720 750 780
Tem
pe
ratu
re (K
)
Pre
ssu
re (
Pa)
Crankangle (deg)
Pressure
Temperature
PVM-MF Dual-Fuel Combustion
Heat release rate
0.0E+00
2.0E+05
4.0E+05
6.0E+05
8.0E+05
1.0E+06
1.2E+06
1.4E+06
1.6E+06
1.8E+06
2.0E+06
700 710 720 730 740 750 760 770 780 790 800
He
at r
ele
ase
rat
e (J
/sec
)
Crankangle (deg)
Diesel Natural gas
PVM-MF Dual-Fuel Combustion
711.5
oC
A
Diesel PV NG T
712oC
A
710oC
A
708oC
A
PVM-MF Dual-Fuel Combustion
717oC
A
Diesel PV NG T
720oC
A
715oC
A
713oC
A
PVM-MF Dual-Fuel Combustion
Fuel-1: Diesel Fuel-2: Natural gas
PVM-MF Dual-Fuel Combustion
Combustion progress variable Temperature
PVM-MF Dual-Fuel Combustion
• Emissions models available in PVM-MF:
– Thermal Nitric Oxide
• Extended Zeldovich Mechanism (Daulch et al. 1973 , Flower et al.1975,
Monat et al. 1979)
– NO mass fraction (used in example)
• Flamelet Library (Lartsson et al. 1998)
– NO mass fraction
– Soot
• Das-Houtz-Reitz (1999) model implemented within ECFM-3Z
– Soot Mass (used in example)
• Moment Method (Lartsson et al. 1998)
– Soot Number Density
– Soot Volume Fraction
– Soot Surface Density
– Soot Mean Diameter
– Carbon Monoxide CO (Hautman et al. 1981)
• CO-CO2 Kinetics Chemistry implemented within ECFM-3Z
– CO mass fraction(used in example)
PVM-MF Dual-Fuel Combustion
Emissions
0.00E+00
1.00E-03
2.00E-03
3.00E-03
4.00E-03
5.00E-03
6.00E-03
7.00E-03
8.00E-03
9.00E-03
800
900
1,000
1,100
1,200
1,300
1,400
1,500
1,600
1,700
700 710 720 730 740 750 760 770 780 790 800
Emis
sio
ns
mas
s fr
acti
on
Tem
pe
ratu
re (K
)
Crankangle (deg)
Temperature
Nox * 10
Soot
CO
PVM-MF Dual-Fuel Combustion
Crank-angle resolved Conjugate Heat Transfer
Purpose of the Model:
• To have an easy-to-use capability for crank-angle resolved
changes in surface temperature. Important for:
Spray impingement – reduced surface temperature
and hence fuel evaporation rate which affects mixture
distribution
Surface coatings of high thermal resistance
• Easy-to-use by specifying a few simple parameters about
the near-surface conducting layer – 1D heat flow
assumption does not need an additional mesh
Crank-angle resolved Conjugate Heat Transfer
Fluid Cell
Solid Layer 1
Solid Layer 2
FSI
SSI
contact resistance
QFF
1
2
3
4
5
6
7
8
B
0
5
10
15
20
25
30
35
40
0.0 1.0 2.0 3.0
Tem
per
atu
re In
crea
se [K
]
Distance from surface [mm]
Temperature Increment vs Time
Time = 1 ms
Time = 5 ms
Time = 10 ms
Minimum temperature on bottom wall as a function of time:
No major differences between the CHT & 1DCHT predictions,
justifying the use of the 1D CHT model
444
445
446
447
448
449
450
0 5 10 15
Min
imu
m W
all T
em
pe
ratu
re [K
]
Time [ms]
BASELINE
CHT
1DCHT
BASELINE CHT 1DCHT
Predicted wall temperature at 15 ms after SOI
432
434
436
438
440
442
444
446
448
450
0 5 10 15
Min
imu
m W
all T
em
pe
ratu
re [K
]
Time [ms]
2.50_80_1.0k
2.50_80_0.5k
2.50_80_0.1k
Thermal properties of the solid has a substantial effect
on wall temperature, with low-conductivity material
experiencing the largest temperature drop
Wall temperature distribution at 15 ms after SOI:
No major differences between the CHT & 1DCHT predictions
Spray-induced heat transfer
Maximum wall temperature increase as a function of time:
No major differences between the CHT & 1DCHT
predictions; verifying the validity of the 1D CHT model
500.0
502.0
504.0
506.0
508.0
510.0
512.0
514.0
0 5 10 15 20 25 30 35 40 45 50
Max
. Wal
l Te
mp
era
ture
[K]
Time [ms]
1DCHT_BaTiO3_1.25mm
1DCHT_Al_5.00mm
BASELINE CHT 1DCHT
Predicted wall temperature 25 ms after SOI
500.0
502.0
504.0
506.0
508.0
510.0
512.0
514.0
0 5 10 15 20 25 30 35 40 45 50
Max
. Wal
l Te
mp
era
ture
[K]
Time [ms]
Maximum Wall Temperature vs Time
BASELINE
CHT_1.25mm
1DCHT_1.25mm
Thermal properties of the solid has a strong effect on wall temperature increase, must be properly accounted for in order to achieve accurate combustion and emissions predictions
Wall temperature distribution 25 ms after SOI:
No major differences between the CHT & 1DCHT predictions
Combustion induced heat transfer
Tair = 800 KPair = 5 barΩ = 2000 rpmYC8H18 = 0.0623
Twall = 500 K (BASELINE)Conduction (CHT)Tbulk = 500 K (1DCHT)
Twall = 500 K
Twall = 500 K
LES
• LES – Collaboration with University of Modena
• Focus on real-engine application:
Cycle-by-cycle variations – COV prediction
Ignition process – AKTIM and ISSIM models
Knock sensitivity – critical for highly rated and
downsized engines
Effect of non-uniform wall temperature – CHT
solution
GRUppoMOtori
Internal Combustion Engine Research
Group
LES – multicycle flame development
2 nd 3 rd 1 st 4 th 5 th
7 th 8 th 6 th 9 th 10 th
12 th 13 th 11 th 14 th 15 th
17 th 18 th 16 th 19 th 20 th
GRUppoMOtori
Internal Combustion Engine Research
Group
Local flow field influence:
4th fastest 16th slowest
LES - 3D Results Insight:
A B
A B
A B
A B
GRUppoMOtori
Internal Combustion Engine Research
Group
LES – Correlation Coefficient
)
)var()var(
),cov((),(
j
jji
YX
YXabsYX
0
0.2
0.4
0.6
0.8
1
ER_local VMAG_local TE_local
Correlation Coefficient (FSD_transition, Yj)
FSD_transition VS Yj (20 cycles)
CCV itself relevantly depends on the FSD_transition CCV. This parameter (thus the transition between the ignition model and the FSD equation) is mostly influenced by equivalence ratio and velocity fields close to the spark plug at the spark time occurrence.
GRUppoMOtori
Internal Combustion Engine Research
Group
Mapped Wall Temperature • Conjugate Heat Transfer (CHT)
analyses in Star-CCM+ to calculate the
local heat transfer
• A realistic point-wise wall thermal field
is applied to LES knocking
combustion
Mapped Wall Temperatures
Piston Crown Combustion Dome
GRUppoMOtori
Internal Combustion Engine Research
Group
Effect of Mapped Wall on Knock
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
730 740 750 760 770 780 790 800
[W]
Crank Angle
Heat Release Rate - Autoignition
Uniform Wall - Fast Cycle Uniform Wall - Medium Cycle Uniform Wall - Slow Cycle
Mapped Wall - Fast Cycle Mapped Wall - Medium Cycle Mapped Wall - Slow Cycle
• A more accurate prediction of knock is obtained
• Knock onset and intensity prediction benefit from the point-wise
thermal field SAE Paper 2013-01-1088
• Meshing technology is critical to the ease-of-use
and accuracy of in-cylinder calculations
• In addition to the existing es-ice meshing
methodology new methods have been developed for
use with IC Engine flows
• The options that will become available are:
More automation of the existing es-ice meshing
Technology based on morphing/remeshing/mapping –
available in 2014
Overset mesh – STAR-CCM+ technology
Meshing for IC Engines
Excellent quality 2D mesh…
Improved fully automatic 2D meshing
Aligned mesh between parallel features improves quality
Improved fully automatic 2D meshing
Fully automatic 3D template generation
2D with Features
Fully automatic 3D template generation
3D Automatic
Fully automatic 3D template generation
3D Automatic
Period: TDC > 30o ABDC (210o)
Total of 6 meshes
Max cells ~ 1.5M at BDC
Period: TDC > 30o ABDC (210o)
Scalar Flow & Mixing
Morphing/Remeshing/Mapping - Setup
Mesh generated at this time
Mesh morphed
in - time Mesh morphed
in + time
Solution mapped
to next mesh
• Different types of meshes may be used at different
stages of the calculation
Meshing Options
Constrained Polyhedra Core Cartesian Mesh Prism Layers Polyhedral Mesh
Local Coordinate Systems
and Local Mesh Refinement
Variable number
of prism layers
Example: 4-valve Gasoline Engine
Details around valve at low and high lifts
2-valve Gasoline with polyhedral mesh
2-valve Gasoline with polyhedral mesh
Inclusion of Spray-Adapted Mesh
The same concept can be used
to embed a local coordinate
system for eg a spray-adapted
mesh in a gasoline engine
Selected morphing used to
control mesh motion
Gasoline Spray-Adapted Mesh
Period: TDC > 30o ABDC (210o)
Spray-adapted mesh between
80o BBDC > 50o BBDC
Total of 7 meshes
Max cells ~ 1.5M at BDC
Gasoline Spray-Adapted Mesh
Period: TDC > 30o ABDC (210o)
Spray-adapted mesh between
80o BBDC > 50o BBDC
Total of 7 meshes
Max cells ~ 1.5M at BDC
STAR-CCM+ Meshing Developments for ICE Simulation
Overset Mesh - the volumes are meshed and motions are
applied to each moving region
STAR-CCM+ Meshing Developments for ICE Simulation
Intake charge scalar animation
ICE in STAR-CCM+
• CD-adapco is accelerating the development of full
Internal Combustion Engine capabilities in STAR-CCM+
• Development and
Support of ICE in
STAR-CD will
continue indefinitely
Summary
• Significant Developments in all key areas:
Combustion models – multi-fuel, emissions developments
Fuels – open format for fuel chemistry libraries
Sprays – wall impingement models
Crank-angle resolved conjugate heat transfer
LES
• New automated and accurate meshing technologies
• Accelerated development of full ICE capability in
STAR-CCM+
