Validation and Verification of ANSYS Internal Combustion Engine Software
Martin Kuntz, ANSYS, Inc.
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 2
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 3
Definitions • Verification – Verify, that model is implemented correctly – Characteristics
• Simplified geometry • Focused on single physical model • Compare to analytical or other CFD
2012 Automotive Simulation World Congress 4 Wednesday, October 10, 2012
• Validation – Demonstrate simulation accuracy – Characteristics
• Realistic geometry • A combination of physical models • Compare to experimental data
• Demonstration – Illustrate application of software to generic case – Characteristics
• Realistic geometry • A combination of physical models • No comparison to data
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 5
IC Engine Simulations Types
• Component simulations
– Intake port, intake manifold, water jackets, fuel injectors
– Spray bomb
• IC engine simulations
– Cold flow • Charge motion
– Combustion • Thermal management
• Emissions
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 6
ICE Simulation Workflow
• Internal combustion engine simulation components – Preprocessing
• Geometry decomposition • Initial meshing • Simulation parameter definition
– Moving deforming meshes • Smoothing, remeshing, layering
– Particle tracking • Injection, tracking, evaporation, wall-interaction
– Combustion • Ignition, flame front propagation
– Post-processing • Automatic processing of monitor and solution data
2012 Automotive Simulation World Congress 7 Wednesday, October 10, 2012
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 8
Demonstration : Direct Injection Gasoline Engine
• Complete cycle setup – Initial conditions and boundary
conditions provided by 1D simulation
– Material Iso-octane
– Spray injection • 6-hole injector
• Double injection
• Transient mass flow
• Prescribed diameter distribution
– Liquid evaporation model
– Spark ignition
– G equation combustion
• Testcase provided by BMW
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 9
Courtesy: BMW
Demonstration : Direct Injection Gasoline Engine
• Initialization
– Burned conditions at EVO
• Boundary condition
– Specified temperature
• Mesh size: cell count
– 800.000 (TDC) to 1.600.000 (BDC)
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 10
Demonstration : Direct Injection Gasoline Engine
• Simulations
– Cold flow run
– Charge motion
• Plus spray injection
• Plus particle tracking
– Combustion • Plus ignition
• Plus flame front propagation
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 11
Demonstration : Direct Injection Gasoline Engine
• Cold flow simulation – Results for CFX and Fluent – Cylinder averaged values of pressure and temperature
Wednesday, October 10, 2012 12
Demonstration : Direct Injection Gasoline Engine
• Cold flow simulation – Results for CFX and Fluent – Swirl ratio, tumble ratio
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Demonstration : Direct Injection Gasoline Engine
• Velocity vector plots
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CA 330
CA 715 CA 555
CA 440
Demonstration : Direct Injection Gasoline Engine
• First injection
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Demonstration : Direct Injection Gasoline Engine
• Evaporation
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Demonstration : Direct Injection Gasoline Engine
• Second injection
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Demonstration : Direct Injection Gasoline Engine
• Total particle mass
• Influence of wall film model
Demonstration : Direct Injection Gasoline Engine
• Combustion simulation
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 19
Demonstration : Direct Injection Gasoline Engine
• Burned flow simulation – Cylinder averaged values
• Pressure • Temperature • Mixture fraction
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress
20
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 21
Validation: Particle Tracking
• Particle injection – Primary / secondary breakup – Injection type: cone / hollow
cone
• Tracking – Particle-wall interaction – Wall film modeling
• Evaporation
• Testcases – Bosch spray box (cold spray) – Hiroyasu spray box (cold spray) – Koss spray (hot spray)
• Two cases based on experimental data from ROBERT BOSCH GmbH
• Details of experimental setup
Setup # 1 Setup # 2
Gas parameters
Gas type N2
Temperature [K] 300
Pressure [MPa] 0.11 0.56 Fuel Properties
Fuel type Heptane
Density [kg/m3] 614.2
Surface tension [kg/s2] 0.0201
Spray parameters
Initial temperature [K] 300
Nozzle diameter [mm] 0.151
Injection pressure [MPa] 10
Injection velocity [m/s] 138
Particle mass flow rate [g/s] 1.5
Injection rate, single pulse [ms] 1.5
Estimated initial spray angle [deg] 5.2 12
Injection Weber number 85 450
sampling point (0, 0.00275, 0.03) 0.03 m
0.00275 m
Available data
• Spray penetration over time
• Sampling point (0, 0.00275, 0.03)
- Droplet diameter distribution
- Droplet velocity distribution
Kumzerova, E. and Esch, T., “Extension and Validation of the CAB Droplet Breakup Model to a Wide Weber Number Range”, Proc. of the 22nd Europ. Conf. on Liquid Atomization and Spray Systems, Paper ILASS08-A132, Como Lake, 2008.
Validation: Bosch Spray Box
Validation: Bosch Spray Box
• Mesh dependence study
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 24
Grid Number of
cells
Size of the cell near the
nozzle [m2]
(radial x axial length)
Coarsest 364 12.8e-4 x 12.8e-4
Coarse 735 6.4e-4 x 6.4e-4
Medium 1450 3.2e-4 x 3.2e-4
Fine 2880 1.6e-4 x 1.6e-4
Finest 5824 8e-5 x 8e-5
Fine Finest
Medium Coarse Coarsest
Validation: Bosch Spray Box
• Mass penetration
• Mesh dependence study
• Fluent simulation
• Setup #2
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 25
Validation: Bosch Spray Box
• Local spray results at sampling point
– Droplet diameter distribution
– Local velocity distributions
– KH-RT breakup model
– Setup #1
Validation: Bosch Spray Box
• Local spray results at sampling point
– Droplet diameter distribution
– Local velocity distributions
– KH-RT breakup model
– Setup #2
Validation: Bosch Spray Box
• Mass penetration
• Comparison KH-RT and SSD break-up model
• Fluent simulation
• Setup #2
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 28
Validation: Bosch Spray Box
• Mass penetration
• Comparison of break-up models
• CFX simulation
• Setup # 2
T i m e [ s ]
P e n
e t r a
t i o n D
e p t h
[ m ]
0 0 . 0 0 0 5 0 . 0 0 1 0 . 0 0 1 5 0 . 0 0 2 0
0 . 0 2
0 . 0 4
0 . 0 6
0 . 0 8
0 . 1 E x p e r i m e n t N o b r e a k u p R e i t z & D i w a k a r S c h m e h l T A B E T A B C A B
M e d i u m g r i d ( 4 0 0 0 n o d e s ) d t = 2 e - 6 s
Validation: Hiroyasu Spray Box
Case 1 Case 2 Case 3
Gas parameters
Gas type N2
Temperature [K] 300 300 300
Pressure [MPa] 1.1 3.0 5.0
Fuel Properties
Fuel type C12H26
Density [kg/m3] 840
Surface tension [kg/s2] 0.0205
Spray parameters
Initial Temperature [K] 300 300 300
Injection Velocity [m/s] 102 90 86
Particle Mass Flow
Rate [g/s] 6.05 5.36 5.13
Nozzle diameter [mm] 0.3 0.3 0.3
Injection rate, single
pulse, ms 2.5 4 4
Validation: Hiroyasu Spray Box
• Mass penetration
• Case 1, 2 and 3
• Fluent simulation
Validation: Koss Spray Box
Gas Temperature [K] 800
Gas Pressure [MPa] 5
Gas Type N2
Particle Mass Flow Rate [g/s] 4.62
Droplets type nHeptane (C7H16)
Density [kg/m3] 684
Surface tenstion [N/m2] 0.02
Nozzle diameter [mm] 0.2
Injection rate [ms] 1.3
Droplet diameter [mm] 0.2
Injection Velocity [m/s] 215
Initial spray angle [deg] 10.1
Measurements: H. Koss, D. Bruuggemann, A. Wiartalla, H. Backer, and A. Breuer, Results from Fuel/Air Ratio Measurements in an N-Heptane Injection Spray, IDEA periodic report, RWTH Aachen, 1992.
• Evaporating spray
– Liquid penetration at 90% spray mass fraction
Liquid penetration Length
Validation: Koss Spray Box
• Breakup model comparison
– TAB
– ETAB
– CAB
– Reitz
• CFX run
Wednesday, October 10, 2012
Validation: Koss Spray Box
• Comparison
– Fluent KH-RT model
– CFX TAB model
Wednesday, October 10, 2012
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 35
Validation: Hamamoto Testcase
• Premixed combustion in a closed vessel with fixed wall
• Propane/air mixture:
– Equivalence ratio =1.0
• Measured data
– Optical access
– Pressure transducer
– Described in • Hamamoto et al. (1988)
• Ewald (2005) Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 36
Validation: Hamamoto Testcase
• Average cylinder pressure
– Mesh sensitivity study Fluent, 2d quad meshes
– Comparison CFX vs. Fluent
Validation: Hamamoto Testcase
• Average cylinder pressure
– Comparison of mesh size and types
– 3D hexahedral and tetrahedral meshes
• Premixed combustion • Flat head, flat piston, SI ICE • Fuel: C3H8
• References: – Alkidas (1980) – Han and Reitz (1997)
• Simulated interval [-30;30 CA] ATDC • Piston motion
Displacement [m3] 0.82 x 10-3
Bore x Stroke [mm] 105.0 x 95.25
Compression ratio 8.56
Connecting rod length [mm] 158
TDC clearance [mm] 12.6
Equivalence ratio 0.87
Engine speed [rpm] 1500
Spark timing [deg. ATDC] -27
Volumetric efficiency 40
Combustion Validation: Pancake Engine
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 39
Combustion Validation: Pancake Engine
• Average cylinder pressure
• G equation combustion
• Comparison
– CFX
– Fluent
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 40
Contents
• Definitions
• Internal Combustion Engines
• Demonstration example
• Validation & verification
– Spray box
– Combustion
– Port flow applications
– IC engine applications
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 41
ICE Validation
• IC engine applications
– Public engine cases
– Collaborations with customers
– Benchmark for customers
– Of interest
• Valuable experimental data
• No confidentiality
• No restrictions for publication
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 42
ICE Validation: Engine Applications
• Port flow simulation
– Thobois generic engine
• Cold flow simulation
– Bosch: direction injection diesel engine with PIV data
• Partially premixed combustion
– Wisconsin: direct-injection spark-ignition engine
• Premixed combustion
– Ducati: premixed engine setup
• Diesel combustion
– Engine cooling simulation
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 43
ICE Validation: Port Flow
• Steady intake flow conditions • Testcase defined in – Large Eddy Simulations in IC Engine Geometries
• Thobois, Rymer, Souleres, Poinsot • SAE Paper, 2004-01-1854
Port length 132 mm Inner port diameter 16 mm Outer port diameter 34 mm Valve opening 10 mm Cylinder length 300 mm Cylinder diameter 120 mm
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 44
ICE Validation: Port Flow
• Comparison
– RANS SST model
– LES SAS model
• CFX results
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 45
Isosurface
Color – eddy viscosity
622 10S
ICE Validation: Port Flow
• Plane @ 20 mm
• Mean Axial Velocity • Axial Velocity Fluctuation
ICE Validation: Port Flow
• Plane @ 70 mm
• Mean Axial Velocity • Axial Velocity Fluctuation
Validation: Bosch Engine
• Experiment – Investigation of Diesel engine in-cylinder flow with Particle Image
Velocimetry (PIV) and High-Speed PIV – Generation of a comprehensive and high-quality database for Large
Eddy Simulation • Simulation – RANS & Scale resolving turbulence models, e.g. LES, DES – CFX simulation
• Publications – “A Strategy for Evaluation of LES Applied to Diesel Engine In-
Cylinder Flow – Joint Effort of Simulation and Experimental PIV Flow Analysis” – Les Rencontres Scientifiques de l'IFP – LES for Internal
Combustion Engine Flows - 18-19 November 2010 – Analysis of In-Cylinder Air Motion in a Fully Optically Accessible
2V-Diesel Engine by Means of Conventional and Time Resolved PIV – 9TH INTERNATIONAL SYMPOSIUM ON PARTICLE IMAGE
VELOCIMETRY – PIV’11, Kobe, Japan, July 21-23, 2011
NR z
s
2
V
V
Vr
Vvr
d
d
2
-1
0
1
2
3
4
5
360 450 540 630 720
[cad]
Sw
irl R
ati
o [
-]
Simulation
Experiment
CFX ICE Swirl
Validation: Bosch Engine
• RANS simulation
– Flow characteristics swirl
Average swirl on planes
Experiment (plane data)
Swirl ration in cylinder
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 49
Validation: Bosch Engine
• Scale Resolving Models
– LES – Large Eddy Simulation
– DES – Detached Eddy Simulation
– SAS – Scale Adaptive Simulation
• Grid size:
– 1.2 – 6.8 · 106 nodes
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 50
Validation: Bosch Engine
• Comparison of velocity profiles – Sample line: -10mm below
dome – Exp: 2D-2C absolute velocity
Sim: 3D-2C absolute velocity
Sample Line
Validation: Wisconsin Engine
• Research project conducted at University of Wisconsin sponsored by ANSYS Inc. – “Characterization of Direct-Injection
Spark-Ignition Operation and Investigation of Particulate Matter Formation"
– Research work of single-cylinder direct-injection spark-ignition engine
– November 2011 – November 2013
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 52
• Riccardo Hydra Base
• Modern DISI engine architecture
Engine Specifications
Engine Type 4-Stroke, 4-Valve, SI
Chamber Geometry Pentroof
Fueling type Spray-guided direct-
injection
Displacement 692.9 cm3
Compression Ratio 12:1
Injection Pressure 11 MPa
Single-cylinder direction-injection spark-ignition engine used for
measurements
Validation: Wisconsin Engine
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 53
Validation: Wisconsin Engine
• Phase 1 single cylinder metal engine – Motored operation – Fired homogeneous (fully vaporized) spark-ignition
operation with premixed air/fuel mixtures – Direct-injection spark-ignition operation
• Phase 2 detailed investigations – Detailed spray characterization measurements in a
spray vessel – Laser-based in-cylinder measurements to characterize
the velocity field or fuel distribution – Detailed measurements of particulate matter number
count
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 54
Validation: Wisconsin Engine
• Motored Engine Measurements
• Repeatability • Influence of coolant temperature
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 55
In-cylinder pressure for 2000 rpm 80 kpa, 80 oC intake, 80 oC coolant
4
6
81
2
4
6
810
2
Cyl
ind
er
Pre
ssu
re [
ba
r]
5 6 7 8 9
0.12 3 4 5 6 7 8 9
1
Volume [L]
Validation: Ducati Engine
• 4-stroke S.I. P.F.I. race engine
• Premixed combustion
• Validation / verification
– Pressure trace
• Collaboration
– University of Bologna, Ducati Motor Holding & ANSYS
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 56
• Publication – ”Flexible Meshing Process and Multi-cycle Methodology for
Simulating Reacting Flows in High Performance SI Engines with ANSYS CFX” • International Multidimensional Engine Modeling User’s Group Meeting
2010 (IMEM 2010), Detroit, April 12th, 2010
Validation: Ducati Engine
• Simulation with CFX
– Efficient multi-cycle methodology
• Single-cycle initialization / multi-cycle initialization
– Influence of mesh resolution & types
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 57
Validation: Ducati Engine
• Simulation with Fluent
– Variation of combustion models / turbulent flame speed models and settings
-20
0
20
40
60
80
100
120
140
-360 -270 -180 -90 0 90 180 270 360
EX
P.
MEA
N I
N-C
YLIN
DER
PR
ES
SU
RE
[bar]
CRANK ANGLE [deg. ATDC]
10000 rpm -Cyl_Horiz10000 rpm -Cyl_VertECFM - cycle 1
C-eqn - cycle 1
G-eqn - cycle 1
G-eqn zcd - cycle 1
G-eqn p - cycle 1
G-eqn pc - cycle 1
Ave
rage
cyl
ind
er p
ress
ure
[b
ar]
Crank Angle [deg] 2012 Automotive Simulation World Congress 58 Wednesday, October 10, 2012
Validation: Engine Cooling Simulation
• Perform Engine Cooling Simulation
– Requires simultaneous simulation • IC engine simulation
• Cylinder head coolant channel simulation
– Thermal inertia of two models is orders of magnitude different two separate simulations
2012 Automotive Simulation World Congress 59 Wednesday, October 10, 2012
Validation: Engine Cooling Simulation
Temperature profile on the firedeck
Time-averaged Heat Flux profile on cylinder
head
Steady state conjugate heat
transfer of cylinder head
Transient combustion
simulation in diesel engine
in-cylinder
Iterative Process
Validation: Engine Cooling Simulation
Import: temperature data
Export: time-averaged heat flux from IVC to EVO
Iteration process
Validation: Engine Cooling Simulation
y+~ 200 y+~ 30
y+~ 20 y+~ 1
• Heat Flux
• n-heptane 1 step mechanism
• Effect of mesh resolution
2012 Automotive Simulation World Congress 62 Wednesday, October 10, 2012
Validation: Engine Cooling Simulation
• Heat Flux
• n-heptane 1 step mechanism
• Effect of combustion and turbulence model
Laminar Finite Rate
K-epsilon
Finite Rate - Eddy
SST K-w SST K-w
Laminar Finite Rate
2012 Automotive Simulation World Congress 63 Wednesday, October 10, 2012
Finite Rate - Eddy
K-epsilon
Validation: Engine Cooling Simulation
• Temperature data at locations of thermocouples
– Heat Flux n-heptane 1 step mechanism + SST k model (Laminar Finite Rate)
Wednesday, October 10, 2012 2012 Automotive Simulation World Congress 64
Summary
• Validation and verification examples related to internal combustion engines – Basic spray and combustion cases – Port flow applications – Cold flow IC engine applications – Combustion IC engine applications
• Good agreement of results for most cases in different application areas
• Ongoing work in the ICE validation project at ANSYS – Continuation of work with existing engines – Collection of new validation cases – Reference cases for current ICE software and future
software developments
2012 Automotive Simulation World Congress 65 Wednesday, October 10, 2012
Any Questions ?
2012 Automotive Simulation World Congress 66 Wednesday, October 10, 2012