In-Cylinder Engine Calculations: New Features and Upcoming ...mdx2.plm.automation.siemens.com/sites/default/files/Presentation/... · 04/12/2013 · •Extended Zeldovich Mechanism

In-Cylinder Engine Calculations:

New Features and Upcoming

Capabilities Richard Johns & Gerald Schmidt

Contents • Brief Review of STAR-CD/es-ice v4.20

Combustion Models

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 Models

• Combustion Models

ECFM-3Z - Multi-fuel capability

ECFM-CLEH - further development of emissions models -

NORA NOx model, CO, soot

PVM-MF - First Release

Open Format for Fuel Libraries – User chemistry mechanism

• Why do we have 3 combustion models?

ECFM-CLEH will become the successor to ECFM-3Z

PVM-MF combines the G-equation and flamelet concepts

Spray Models – Wall Impingement

• Spray Models - Senda Droplet-Wall Interaction Model

• Developed by Prof. Senda at Doshisha University, Japan

• Covers three boiling heat transfer regimes with distinct

submodels and extensive validation

Temperature = 398 K, Pressure = 0.5 MPa

2.1 ms

2.5 ms

2.9 ms

Liquid Phase Vapor Phase

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


Group

Local flow field influence:

4th fastest 16th slowest

LES - 3D Results Insight:

A B

A B

A B

A B

GRUppoMOtori


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


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


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

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


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


711.5

oC

A

Diesel PV NG T

712oC

A

710oC

A

708oC

A


717oC

A

Diesel PV NG T

720oC

A

715oC

A

713oC

A


Fuel-1: Diesel Fuel-2: Natural gas


Combustion progress variable Temperature


• 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)


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



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


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

Spray-induced heat transfer

• Cylindrical chamber, stationary mesh

• 20 mg of liquid C8H18 sprayed toward the

bottom wall

• 3 runs to validate the 1D CHT model

• BASELINE: bottom wall at a fixed temperature of

450 K

• CHT: 5 mm aluminum slab at bottom wall for 3D

conjugate heat transfer calculation

• 1DCHT: BASELINE mesh with 1D CHT model

activated at bottom wall

• 3 runs to examine the effect of material

property on wall temperature change

• 1.0k: standard aluminum property

• 0.5k: conductivity reduced by 50%

• 0.1k: conductivity reduced by 90%

• 20 mg of C8H18

• Tfuel = 293 K• Duration = 5 ms• Nozzle size = 0.2 mm

Tair = 350 KPair = 1 bar

Twall = 350 K

Twall = 350 K

Twall = 450 K (BASELINE)Conduction (CHT)Tbulk = 450 K (1DCHT)

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

Combustion induced heat transfer

• Cylindrical chamber, stationary

mesh

• Premixed air & C8H18, ignition at

chamber center

• 3 runs to validate the 1D CHT

model with 1.25mm BaTiO3

(barium titanate) layer • BASELINE: bottom wall at a fixed

temperature of 500 K

• 1DCHT: BASELINE mesh with 1D CHT

model activated at bottom wall

• CHT: slab at bottom wall for 3D

conjugate heat transfer calculation

• 2 runs to examine the effect of

material property on wall

temperature change • BaTiO3 (1.25 mm)

• Aluminum (5 mm)

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

BaTiO3 Aluminum

Density [kg/m3] 5840 2702

Thermal conductivity [W/mK] 2.6 237

Heat capacity [J/kgK] 434 903

Thickness [mm] 1.5 5.0

t = 2.5 ms t = 5.0 ms t = 15.0 ms

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

• Multiple solid layers with contact resistance at solid-solid interfaces

• 1D energy balance on each solid cell

• Boundary conditions:

• Given heat flux (QF) from the fluid side (computed inside STAR-CD)

• Specified bulk temperature (TB) at the solid side (specified by user)

• Resulting equations give a tri-diagonal system which is solved very

efficiently

• Works with all existing STAR-CD models:

Liquid Film

Spray

Combustion

Boiling etc.

• Available early 2014

Summary of 1D CHT Model

• 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

Period: TDC > 30o ABDC (210o)

Total of 6 meshes

Max cells ~ 1.5M at BDC


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


Spray-adapted mesh between

80o BBDC > 50o BBDC

Total of 7 meshes

Max cells ~ 1.5M at BDC

Gasoline Spray-Adapted Mesh

Scalar Field from Intake Flow

Overset Mesh

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+

Documents

In-Cylinder Engine Calculations: New Features and Upcoming ...mdx2.plm.automation.siemens.com/sites/default/files/Presentation/... · 04/12/2013 · •Extended Zeldovich Mechanism