Ismail - openfoam internal combustion engines

Harun M. Ismail1, Xinwei Cheng1, Hoon Kiat Ng1, Suyin Gan1 and Tommaso Lucchini2

1 Department of Mechanical, Materials and Manufacturing EngineeringUniversity of Nottingham (Malaysia Campus)

2 Dipartimento of Energia, Politecnico di Milano, Italy

Meeting on Internal Combustion Engine Simulations Using OpenFOAM, Milan, Italy , 2011

Numerical Study on the Combustion and Emission

Characteristics of Different Biodiesel Fuel Feedstocks and

Blends Using OpenFOAM

Introduction

Motivation

� Both conventional petroleum industry and bio-fuel industry (Palm Oil) is a multi-million dollar business in

Malaysia (biggest Palm Oil exporter in the world )

� Limited petroleum resources and increasing emission standards

� Bio-fuels still at its infancy stage, the development of theories to understand its combustion and emission nature

is not widely available

Objectives of this work

� Development and applications fuel thermo-physical and transport properties of Coconut (CME), Palm (PME) and

Soy methyl-esters (SME) for in-cylinder (IC) spray combustion CFD modelling

� Development and applications of generic reduced combustions kinetics suitable for CME, PME and SME for CFD ,

IC engine applications

� Analyse the influence and relation between fuel properties and fuel spray structures for different biodiesel/diesel

blend levels (B0 – B100) and fuel type

� Investigate combustion and emission characteristics for different blend levels and fuel type (CME, PME and SME)

1Meeting on Internal Combustion Engine Simulations Using OpenFOAM, Milan, Italy , 2011

Biodiesel Thermo-physical & Transport Properties

� Properties calculated using “Group contribution method”

� Evaluation of fuel thermo-physical properties & transport properties up to the critical temperature

of a respected fuel


Type ofFatty-acids

Chemical Formula

Soy %

Palm %

Coconut %

Saturated C12H26O2 - - 48Saturated C15H30O2 - - 17Saturated C11H22O2 - - 9Saturated C17H34O2 18 42 8Saturated C19H38O2 7 5 -Unsaturated C19H36O2 10 41 18Unsaturated C19H34O2 60 10 -Unsaturated C19H32O2 10 2 -

Property CME PME SME

Critical Temperature (K) 773.5 789.2 721.2

Critical Pressure (bar) 14.0 13.0 15.3

Critical Volume (ml/mole) 1064.0 1084.0 885.0

Bio-fuel components

•Based on information

compiled from open

literature and lab fuel test

•Five largest contributing

components of ME are

identified for properties

computation

Biodiesel Thermo-physical & Transport Properties

6Meeting on Internal Combustion Engine Simulations Using OpenFOAM, Milan, Italy, 2011

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

280 380 480 580 680 780

Vap

our

Th

erm

al C

ond

uctiv

ity /

[W/m

-K]

Temperature (K)

DieselCMEPMESME

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

280 380 480 580 680 780

Vap

our

Diff

usiv

ity /

log[

m^2

/s]

Temperature (K)

DieselCMEPMESME

0.0E+00

2.0E-05

4.0E-05

6.0E-05

8.0E-05

1.0E-04

1.2E-04

1.4E-04

1.6E-04

280 380 480 580 680 780

Vap

our

vis

cosi

ty (P

a-s)

Temperature (K)

B20

B50

B80

Diesel

0

50

100

150

200

250

300

350

400

450

280 380 480 580 680 780

Late

nt h

eat o

f vap

oriz

atio

n (k

J/m

ol)

Temperature (K)

B20

B50

B80

Diesel

Some examples of the PME blends (B0 –B100) as compared to

diesel for illustration

Biodiesel ThermoBiodiesel Thermo--physical & Transport Properties physical & Transport Properties Implementations in OpenFOAM Implementations in OpenFOAM

7

� Snippets of properties implemented in

OpenFOAM fuel library

Interpolate function

were utilised to estimate

fuel properties at

different temperatures


Experimental Setup (Nottingham Research Engine)

� Experimental engine consists of 4-hole injector at 90o apart

� A 90o 3D-model of the combustion chamber is generated

� The mesh set with 1 injector hole at 45o from X and Y axis.

� Dynamic mesh with cell size of 1mm

8

Nottingham Research Engine SpecificationsEngine Type Light-Duty DieselPiston Type Bowl-in-pistonDisplacement Volume per-cylinder 347cm3

Compression Ratio 19 : 1Stroke 69 mmBore 80 mmConnecting Rod Length 114.5 mmIntake Valve Closing (IVC) -140o ATDCExhaust Valve Opening (EVO) 140o ATDCEngine Speed 1500 – 3500 rev/min


Experimental Setup (Chalmers HP/HT Rig)

� Cell size increased from 0.25 to 2 mm

� Chamber size fit to (60 x 60 x 150) mm

� Chamber air density maintained to

match experimental condition at 20.89

kg/m3

9

Fuel Injection

Point

Exhaust Gas Heat

Exchanger

Pressurised Air Inlet

Regulator

Air Heaters

Optically Accessed Chamber

Air Flow Controller

Gas Exit

Raul et al. (SAE 2008-01-1393)

Meeting on Internal Combustion Engine Simulations Using OpenFOAM, Milan, Italy, 2011

Chalmers High Pressure/High Temperature Rig Type Constant Volume

Volume 2.0 l Injection Period 3.5 ms

Injection Pressure 1200 bar Fuel Temperature 313.15 K

Chamber Pressure (constant) 50 barChamber Initial Temperature 830 K

Fuel of Interest Diesel(B0), Palm methyl-ester (B100)

Increasing cell size

Utilised OpenFOAM ICE-Lib (Polimi) Models

10

Atomisation•HuhGosman

Evaporation•standardEvaporationModel

Heat Transfer•RanzMarshall

Wall Model•BaiGosman

Break-up Model•Reitz-KHRT

Dispersion Model•stochasticDispersionRAS

Injector Model•huhInjector

Drag Model•standardDragModel

Injector Type•unitInjector

Collision Model•off

Turbulence Model•RNG-k-epsilon

Combustion Model•PSR model

Wall Heat Transfer Model

•turbulentHeatFlux


Validations of Fuel Thermo-physical & Transport Properties Using OpenFOAM

The thermo-physical and

transport properties validated

against experimental liquid &

vapour axial penetration length


� The simulated spray structure matches with

experimental data with good accuracy

� Fuel spray structure could be simulated using the

developed fuel properties

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Axi

al P

enet

ratio

n Le

ngth

/ [m

]

Time / [ms]

MeasuredDiesel MeasuredPME

SimulatedDiesel SimulatedCME

SimulatedPME SimulatedSME

VpMeasuredDiesel VpMeasuredPME

VpSimulDiesel VpSimulCME

VpSimulPME VpSimulSME

Difference in liquid

penetration length

between diesel B(0) and

biodiesel (B100) fuels

Validations of Fuel Thermo-physical & Transport Properties Using OpenFOAM


� Illustration of the four fuel species distribution contour plot

Biodiesels (B100) have longer

spray penetration length due

to higher viscosity and surface

tension

Biodiesel fuel tends to have

SIMILAR spray and

evaporation structure, but

NOT SAME

The dissimilarities can

be clearly seen in fuel

evaporation simulation

without combustion

Effects of Fuel Thermo-physical & Transport Properties (Fuel Type Comparison)


0.0E+00

1.0E-07

2.0E-07

3.0E-07

4.0E-07

5.0E-07

6.0E-07

7.0E-07

8.0E-07

9.0E-07

-11 -9 -7 -5 -3 -1 1

Eva

po

rate

d M

ass

/ [kg

]

Crank Angle

EvapMassIDEA (B0)

EvapMassCME (B100)

EvapMassPME (B100)

EvapMassSME (B100)

Rate of Evaporation:

Diesel (IDEA) > CME > SME > PME

Mass of fuel injected equal for all fuel

0

10

20

30

40

50

60

70

80

90

100

CME PME SME

Fue

l Co

mp

osi

tion

/ [%

by

vol]

Fuel Type

SaturatedUnsaturated

CAD range before start

of combustion (SOC)

% of Unsaturation

SME > PME > CME

% of individual

composition

that makes up

SME and PME

- 5o CAD

0

50

100

150

200

250

300

350

400

450

500

280 380 480 580 680 780

Hea

t of V

apo

risa

tion

/ [kJ

/kg]

Temperature (K)

DieselCMEPMESME

Effects of Fuel Thermo-physical & Transport Properties (Fuel Type Comparison)


Rate of Evaporation:

Diesel (IDEA) > CME > SME > PME

Mass of fuel injected equal for all fuel

Heat of Vaporisation:

From T = 280 – 650 K

SME < PME

SME can be evaporated

significantly faster

Suggests the importance

of % individual

composition that makes

up SME and PME

0

10

20

30

40

50

60

70

80

90

100

CME PME SME

Fue

l Co

mp

osi

tion

/ [%

by

vol]

Fuel Type

SaturatedUnsaturated

% of Unsaturation

SME > PME > CME

Effects of Fuel Thermo-physical & Transport Properties (Palm B0-B100)


0.0E+00

1.0E-07

2.0E-07

3.0E-07

4.0E-07

5.0E-07

6.0E-07

7.0E-07

8.0E-07

9.0E-07

-11 -9 -7 -5 -3 -1 1

Eva

po

rate

d M

ass

/ [kg

]

Crank Angle

EvapMassIDEA (B0)

EvapMassPME (B20)

EvapMassPME (B50)

EvapMassPME (B80)

EvapMassPME (B100)

B0 B20B50

B80

B100

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100

No

rmal

ised

Eva

pora

ted

Mas

s / [

kg/k

g]

% Blends (PME)

NormalisedEvapMass(B0-B100)

Suggests the

strong influence

of IDEA fuel

(Diesel) up to

80% biodiesel

mixture (B80)

- 5o CAD

Increasing

% of

biodiesel

Development & Applications of Generic Reduced Biodiesel Fuel Surrogate Combustion Kinetics

Motivation

� Computational resources (time & cost)

� Lack of widely available biodiesel

mechanism validated for Palm, Coconut

and Soy methyl-esters

� To investigate the combustion and

emission characteristics of Palm, Soy

and Coconut biodiesel fuels.


Adapted from C.K Law et al. [AIAA 2008-969]

Detailed LLNL methyl-

ester mechanism with

301 species and 1516

reactions

� Reduced and validated for 48 shock-tube

conditions (STC) during entire mechanism

reduction process with comparison the

detailed mechanismReduced mechanism 77 species 212 reactions

0-D (PSR) Validations of Generic Reduced Biodiesel Fuel Surrogate Combustion Kinetics

18

0

1

10

100

1,000

0.60 0.80 1.00 1.20 1.40 1.60

Igni

tion

Tim

e/ [m

s]

1000/T

modifiedLLNL-EQ=0.5

Reduced-EQ=0.5

modifiedLLNL-EQ=1.0

Reduced-EQ=1.0

modifiedLLNL-EQ=1.5

Reduced-EQ=1.5

0.01

0.1

1

10

100

1000

0.60 0.80 1.00 1.20 1.40 1.60

Igni

tion

Tim

e/ [m

s]

1000/T

modifiedLLNL-EQ=0.5

Reduced-EQ=0.5

modifiedLLNL-EQ=1.0

Reduced-EQ=1.0

modifiedLLNL-EQ=1.5

Reduced-EQ=1.5


Gas Phase (PSR) Validations at 48-STC

� Error in ID less than 13 % during 0-D reductions process as compared to LLNL mechanism

� Combine with modified skeletal n-heptane mechanism to match energy content and C/H/O ratio

� ID shown here based on Nottingham Research Engine calibrations

P= 13.5, Ø = 0.5 -1.5

77 species, 212 reactions

P= 41.0, Ø = 0.5 -1.5

77 species, 212 reactions

3-D CFD Validations of Reduced Biodiesel Fuel Surrogate Combustion Kinetics Using OpenFOAM


Diesel

PME SME

� Pressure trace comparison for engine conditions

at 2000 rpm and power 1.5kW

� The simulated spray combustion matches with

experimental data with good accuracy

� Future test will be conducted on constant fuel

mass and constant ID to study the combustion an

emission characteristics for CME, PME and SME

Legend

Measured

Simulatied

Combustion and Emission Characteristics of Palm, Soy and Coconut (B100) Biodiesel Fuels


SOI EOI

� NO plot for engine conditions at 2000rpm

and 1.5 kW of power.

� Start of injection (SOI) and end of injection

(EOI) for all cases are the same

- 4o CAD

ATDC

Change in fuel type leads to

change in NO distributions

Combustion and Emission Characteristics of Palm, Soy and Coconut (B100) Biodiesel Fuels


SME PME- 4o CAD ATDC

NO mass fraction at -4o CAD ATDC

SME > PME

Soot mass fraction at -4o CAD ATDC

SME > PME

• Similar to trend observed in experimental studies

• Three possibilities for the observed trend :

� Mass of fuel injected (SME > PME)

� Ignition Delay (SME > PME)

� Level of usaturation in the fuel (SME > PME)

Conclusions


Conclusions

• Main objectives of development and implementations of biodiesel fuel properties and

combustion kinetics were achieved

• As for preliminary validations, good level of agreement was achieved between computed and

measured data for both fuel properties and combustion kinetics

• Effects of fuel properties and chemical kinetics could be isolated using CFD studies to better

understand the combustion and emission characteristics of biodiesel fuel in CI engines

Acknowledgments


• Authors would like to thank Dr. Tommaso Lucchini for his helpful suggestions and guidance

• Authors would like to thank Internal Combustion Engine (ICE) Group PoliMi for the collaborative

effort given during the research work

• This research work is currently funded by Ministry of Science of Technology (MOSTI) of Malaysia.

Meeting on Internal Combustion Engine Simulations Using OpenFOAM, Milan, Italy, 2011

THANK YOU

Contact email: [email protected]

Internal Combustion Engine GroupEnergy, Fuel and Power Technology Research Division

Department of Mechanical, Materials and Manufacturing EngineeringUniversity of Nottingham (Malaysia Campus)

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Ismail - openfoam internal combustion engines