Validation and Verification of ANSYS Internal ...

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

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Definitions • Verification – Verify, that model is implemented correctly – Characteristics • Simplified geometry • Focused on single physical model • Compare to analytical or other CFD

• 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 Wednesday, October 10, 2012


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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


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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 Wednesday, October 10, 2012


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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 Courtesy: BMW Wednesday, October 10, 2012


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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


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Demonstration : Direct Injection Gasoline Engine • Simulations – Cold flow run – Charge motion • Plus spray injection • Plus particle tracking

– Combustion • Plus ignition • Plus flame front propagation



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Demonstration : Direct Injection Gasoline Engine • Cold flow simulation – Results for CFX and Fluent – Cylinder averaged values of pressure and temperature


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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

CA 330

CA 440

CA 555



CA 715

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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


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Demonstration : Direct Injection Gasoline Engine • Burned flow simulation – Cylinder averaged values • Pressure • Temperature • Mixture fraction

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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)

Validation: Bosch Spray Box • Two cases based on experimental data from ROBERT BOSCH GmbH • Details of experimental setup Setup # 1

Setup # 2

Gas param eters

Gas type Temperature [K] Pressure [MPa]

N2 300

0.11

0.00275 m 0.56

Fuel Properties

Fuel type Density [kg/m3] Surface tension [kg/s2]

0.03 m

Heptane 614.2 0.0201

Available data

Spray parameters Initial temperature [K] Nozzle diameter [mm] Injection pressure [MPa] Injection velocity [m/s] Particle mass flow rate [g/s]

300 0.151 10 138 1.5

Injection rate, single pulse [ms] Estimated initial spray angle [deg] Injection Weber number

1.5 5.2 85

sampling point (0, 0.00275, 0.03)

12 450

• 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 • Mesh dependence study Number of cells

Size of the cell near the nozzle [m 2] (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

Grid

Coarsest

Coarse


Medium

Fine


Finest

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Validation: Bosch Spray Box • • • •

Mass penetration Mesh dependence study Fluent simulation Setup #2



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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



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Validation: Bosch Spray Box Mass penetration Comparison of break-up models CFX simulation Setup # 2 E xperiment 0.1

Penetration Depth [m]

• • • •

0.08

No breakup R eitz &D iwakar S chmehl T AB E T AB C AB

0.06 0.04 0.02 00

0.0005

0.001

Medium grid (4000 nodes) dt = 2e-6 s 0.0015 0.002

Time [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] Droplets type

4.62

• Evaporating spray – Liquid penetration at 90% spray mass fraction

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.

Liquid penetration Length

Validation: Koss Spray Box • Breakup model comparison – TAB – ETAB – CAB – Reitz • CFX run


Validation: Koss Spray Box • Comparison – Fluent KH-RT model – CFX TAB model




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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


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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

Combustion Validation: Pancake Engine • • • •

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

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Combustion Validation: Pancake Engine • Average cylinder pressure • G equation combustion • Comparison – CFX – Fluent



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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


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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


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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 Inner port diameter Outer port diameter Valve opening Cylinder length Cylinder diameter Wednesday, October 10, 2012


132 mm 16 mm 34 mm 10 mm 300 mm 120 mm 44

ICE Validation: Port Flow • Comparison – RANS  SST model – LES  SAS model

• CFX results

Isosurface S 2  2  106 Color – eddy viscosity Wednesday, October 10, 2012


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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 –

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“A Strategy for Evaluation of LES Applied to Diesel Engine InCylinder 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

Validation: Bosch Engine • RANS simulation – Flow characteristics  swirl Rs 

z 2 N

  r  V  v dV  2 r  dV V

5 Swirl Ratio [-]

4 3 2 1

Average swirl on planes Simulation Experiment (plane data) Experiment SwirlICE ration in cylinder CFX Swirl

0 -1 360

450


540

630

720

[cad] 2012 Automotive Simulation World Congress

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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



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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



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Validation: Wisconsin Engine • Riccardo Hydra Base • Modern DISI engine architecture

Engine Specifications

Single-cylinder direction-injection spark-ignition engine used for measurements Wednesday, October 10, 2012

Engine Type

4-Stroke, 4-Valve, SI

Chamber Geometry

Pentroof

Fueling type

Spray-guided directinjection

Displacement

692.9 cm3

Compression Ratio

12:1

Injection Pressure

11 MPa


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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


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Validation: Wisconsin Engine • Motored Engine Measurements • Repeatability • Influence of coolant temperature Cylinder Pressure [bar]

2

10

8 6 4 2

1

8 6

4

5

6 7 8 9

2

3

4

5

6 7 8 9

0.1

1 Volume [L]

In-cylinder pressure for 2000 rpm 80 kpa, 80 oC intake, 80 oC coolant Wednesday, October 10, 2012


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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 • 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 Wednesday, October 10, 2012


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Validation: Ducati Engine • Simulation with CFX – Efficient multi-cycle methodology • Single-cycle initialization / multi-cycle initialization

– Influence of mesh resolution & types



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Validation: Ducati Engine

cylinder pressure [bar] Average EXP. MEAN IN-CYLINDER PRESSURE [bar]

• Simulation with Fluent – Variation of combustion models / turbulent flame speed models and settings


140

10000 rpm Cyl_Horiz 10000 rpm Cyl_Vert ECFM - cycle 1

120

C-eqn - cycle 1

100

G-eqn - cycle 1 G-eqn zcd - cycle 1

80

G-eqn p - cycle 1

60

G-eqn pc - cycle 1

40 20

0 -360 -20

-270

-180

-90

0

90

180

270

CRANK ANGLE [deg. ATDC] Crank Angle [deg]


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360

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



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Validation: Engine Cooling Simulation Transient combustion simulation in diesel engine in-cylinder

Steady state conjugate heat transfer of cylinder head

Time-averaged Heat Flux profile on cylinder head

Iterative Process

Temperature profile on the firedeck

Validation: Engine Cooling Simulation Import: temperature data

Iteration process

Export: time-averaged heat flux from IVC to EVO

Validation: Engine Cooling Simulation • Heat Flux • n-heptane 1 step mechanism • Effect of mesh resolution

y+~ 200

y+~ 20 Wednesday, October 10, 2012


y+~ 30

y+~ 1 62

Validation: Engine Cooling Simulation • Heat Flux • n-heptane 1 step mechanism • Effect of combustion and turbulence model

K-epsilon

Laminar Finite Rate

SST K-w

Laminar Finite Rate Wednesday, October 10, 2012


K-epsilon

Finite Rate - Eddy

SST K-w

Finite Rate - Eddy 63

Validation: Engine Cooling Simulation • Temperature data at locations of thermocouples – Heat Flux n-heptane 1 step mechanism + SST k model (Laminar Finite Rate)



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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 Wednesday, October 10, 2012


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Any Questions ?



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