Validation Verification Internal Combustion Ansys

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




Spray box

Combustion




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




Spray box

Combustion




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


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


Contents

Definitions




Spray box

Combustion




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


Initialization

Burned conditions at EVO

Boundary condition

Specified temperature

Mesh size: cell count

800.000 (TDC) to 1.600.000 (BDC)



Simulations

Cold flow run

Charge motion

Plus spray injection

Plus particle tracking

Combustion Plus ignition

Plus flame front propagation



Cold flow simulation Results for CFX and Fluent Cylinder averaged values of pressure and temperature

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Cold flow simulation Results for CFX and Fluent Swirl ratio, tumble ratio

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Velocity vector plots


CA 330

CA 715 CA 555

CA 440


First injection



Evaporation



Second injection



Total particle mass

Influence of wall film model


Combustion simulation



Burned flow simulation Cylinder averaged values

Pressure Temperature Mixture fraction

Wednesday, October 10, 2012 2012 Automotive Simulation World Congress

20

Contents

Definitions




Spray box

Combustion




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


Mesh dependence study


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


Mass penetration

Mesh dependence study

Fluent simulation

Setup #2



Local spray results at sampling point

Droplet diameter distribution

Local velocity distributions

KH-RT breakup model

Setup #1


Local spray results at sampling point

Droplet diameter distribution

Local velocity distributions

KH-RT breakup model

Setup #2


Mass penetration

Comparison KH-RT and SSD break-up model

Fluent simulation

Setup #2



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


Breakup model comparison

TAB

ETAB

CAB

Reitz

CFX run

Wednesday, October 10, 2012


Comparison

Fluent KH-RT model

CFX TAB model

Wednesday, October 10, 2012

Contents

Definitions




Spray box

Combustion




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


Average cylinder pressure

Mesh sensitivity study Fluent, 2d quad meshes

Comparison CFX vs. Fluent



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


Combustion Validation: Pancake Engine


G equation combustion

Comparison

CFX

Fluent


Contents

Definitions




Spray box

Combustion




ICE Validation


Public engine cases

Collaborations with customers

Benchmark for customers

Of interest

Valuable experimental data

No confidentiality

No restrictions for publication


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


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



Comparison

RANS SST model

LES SAS model

CFX results


Isosurface

Color eddy viscosity

622 10S


Plane @ 20 mm

Mean Axial Velocity Axial Velocity Fluctuation


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 PIV11, Kobe, Japan, July 21-23, 2011

NR zs

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


RANS simulation

Flow characteristics swirl

Average swirl on planes

Experiment (plane data)

Swirl ration in cylinder



Scale Resolving Models

LES Large Eddy Simulation

DES Detached Eddy Simulation

SAS Scale Adaptive Simulation

Grid size:

1.2 6.8 106 nodes



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


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




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



Motored Engine Measurements

Repeatability Influence of coolant temperature


In-cylinder pressure for 2000 rpm 80 kpa, 80 oC intake, 80 oC coolant

4

6

81

2

4

6

810

2

Cyl

inder

Pre

ssure

[bar]

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


Publication Flexible Meshing Process and Multi-cycle Methodology for

Simulating Reacting Flows in High Performance SI Engines with ANSYS CFX International Multidimensional Engine Modeling Users Group Meeting

2010 (IMEM 2010), Detroit, April 12th, 2010


Simulation with CFX

Efficient multi-cycle methodology

Single-cycle initialization / multi-cycle initialization

Influence of mesh resolution & types



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



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


Import: temperature data

Export: time-averaged heat flux from IVC to EVO

Iteration process


y+~ 200 y+~ 30

y+~ 20 y+~ 1

Heat Flux

n-heptane 1 step mechanism

Effect of mesh resolution



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


Finite Rate - Eddy

K-epsilon


Temperature data at locations of thermocouples

Heat Flux n-heptane 1 step mechanism + SST k model (Laminar Finite Rate)


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


Any Questions ?


Documents

Validation Verification Internal Combustion Ansys