Airflow and Fuel Spray Interaction in a Gasoline DI Engine

Instituto Brasileirode Petróleo e Gás

UniversityUniversity ofof

BrightonBrighton

Airflow and Fuel Spray Interaction in a Gasoline DI

Engine

Professor Morgan HeikalProfessor Morgan HeikalInternal Combustion Engines GroupInternal Combustion Engines Group

University of BrightonUniversity of Brighton&&

Ricardo UK LtdRicardo UK Ltd

2

Presentation outline

Area of StudyTest Equipment and

Methods• Mie scatter studies • Backlighting studies• CFD analysis

Results evaluationConclusions

3

Area of Study

Airflow and Fuel Spray Interaction• Early injection regimes• Variation of spray characteristics with

injection timing• Distortion of fuel jet by air flow

Comparison of experiment with CFD analysis• To check on experimental findings

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Test EngineRicardo ‘Hydra’ G-DI research engineSingle-cylinder, wall-guidedFull-quartz optical cylinder linerHeated Piston

throttle

intake plenum

cam box

cam pulleys

cylinder head

exhaust

cylinder liner

timing belt

flywheel

piston head

piston extension

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Engine Combustion ChamberTop entry, pent roof

construction Injector

• side mounted• swirl atomiser • 70o included angle

Spark Plug• centrally located

2d piston profile75mm stroke74mm bore

New diagram including piston profile and spark plug

Get bette

r image and re

-do layo

ut

Get bette

r image and re

-do layo

ut

6

Optical Methods IMie scatter

• 1000 rev/min, WOT, SOI ATDC 20, 40, 60o

Nd:YAG Lasershuttercontrol

Computer CCD Camera

45o mirror

sheet optics

beam dump

Combustionchamber

Nd:YAG Lasershuttercontrol

Computer CCD Camera

45o mirror

sheet optics

beam dump

Combustionchamber

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Optical Methods II

Backlighting studies• 1000 rev/min• WOT• SOI

• ATDC 20, 40, 60o

Computer

Combustionchamber

flash lamps

Flash trigger

ImaconHigh Speed Camera

Light diffuser

Computer

CombustionchamberCombustionchamber

flash lamps

Flash trigger

ImaconHigh Speed Camera

Light diffuser

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CFD AnalysisCFD Code

Ricardo VECTIS Fuel spray model

Discrete droplet model (DDM) Ensemble of droplet parcels Introduction rate given by

injection rate spray angle droplet size distribution

Secondary break-up sub-models Droplet turbulence interaction and impingement Secondary break-up model – Reitz-Diwakar

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Mie Scatter Results I

(a)

Raw average image

(b)

Thresholded image

Masked image

(c)

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Mie Scatter Results II

(a) (b) Edge detection

Injection progress

(c)

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Mie Scatter Results III

6CA 9.6CA

13.2CA 16.8CA

SOI = 20CA ATDC SOI = 20oATDC

SOI = 40A

ATDC SOI = 40oATDC

SOI = 60oATDC

SOI = 60CA ATDC

SOI = 80oATDC

SOI = 80A ATDC

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Backlighting Results I

Averaged imageintake valves

Edge detectedintake valves

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Backlighting Results IISpray width intensity profile analysis

30 pixel

60 pixel

90 pixel

30 pixel

60 pixel

90 pixel

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CFD Analysis Ispray shadow

central planend2

air speedvapour

air speed on valve CL

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CFD Analysis IIMie Scattering CFD nd2 – 1mm CFD spray chop 1mm CFD whole spray CFD vapour phase CFD velocity J18 CFD velocity J26 CFD velocity J34

24.8o

24.8o

24.8o

24.8o

24.8o

24.8o

24.8o

26.0o

26.0o

26.0o

26.0o

26.0o

26.0o

26.0o

27.2o

27.2o

27.2o

27.2o

27.2o

27.2o

27.2o

28.4o

28.4o

28.4o

28.4o

28.4o

28.4o

28.4o

29.6o

29.6o

29.6o

29.6o

29.6o

29.6o

29.6o

Comparison of results of CFD analysis with experiment

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CFD Comparison with Experiment

SOI 60o CA8o ASOI

SOI 60o CA21o ASOI

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0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

0

0.1

0.2

0.3

0.4

0.5

0.6

Fu

el In

jectio

n R

ate

20CA

FuellingRate

SOI EOI

Intensity variation with SOI

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

0

0.1

0.2

0.3

0.4

0.5

0.6

Fu

el In

jectio

n R

ate

20CA

40CA

FuellingRate

SOI EOI

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

0

0.1

0.2

0.3

0.4

0.5

0.6

Fu

el In

jectio

n R

ate

20CA

40CA

60CA

FuellingRate

SOI EOI

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

0

0.1

0.2

0.3

0.4

0.5

0.6

Fu

el In

jectio

n R

ate

20CA

40CA

60CA

80CA

FuellingRate

SOI EOI

Analysis of Mie Scatter Data

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Backlighting evidenceAverage spray width at 3 depths

•For 1.2, 1.6, 2.0, 2.4, 2.9ms ASOI•Width decreases with later SOI

0

5

10

15

20

25

30 40 50 60 70 80 90SOI

Sp

ray

wid

th (

mm

)

30 pixel

60 pixel

90 pixel

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0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

20CA

40CA

60CA

80CA

SOI EOI

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

20CA

40CA

60CA

80CA

SOI EOI

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35Crank Angles ASOI

N

orm

alis

ed

Inte

nsi

ty

20CA

40CA

60CA

80CA

SOI EOI

Comparison with CFDCFD nd2 values

• Similar increase with SOI• Similar fluctuations CFDMie scatterCFD

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Intensity Increase with SOI

Central plane intensity onlyJet squeezed by incoming air from valvesPlume shape changed

• Flattened in cross-tumble plane• Broadened in tumble plane

More fuel is maintained in central planeDue to increased valve lift and air flow with later

SOICould have been due to changes in droplet size

• Checked against Begg(2003) and eliminated

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Intensity Irregularity with SOI

Comes from jet flapping• Seen in

vapour distribution

• Valid indicator for early stages

• Clearest visualisation

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Measured Jet flapping

Video representation• Jet flap at start• As CFD image• Despite average

image• Rotational

oscillation?• Takes fuel in and

out of central plane

• Explains intensity fluctuation with SOI

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Backlighting ImageOscillation also seen in this

plane

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Backlighting ImageOscillation also seen in this

plane

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ConclusionFor early injection, incoming air acts on fuel jet

• Air flow from two valves flatten jet• Fuel squeezed towards central pane• Effect increases with SOI delay

• Shows as increasing Mie signal coverage and intensity • Due to increasing air flow as valve opening and piston speed increase

• Narrowing seen in other plane • Fuel jet is deflected downwards

Jet is seen to oscillate• Visible from Mie and backlighting data perspective• Manifests as irregularity in Mie signal through injection process

CFD Analysis • Confirms effect if air inflow on jet• Predicts oscillation of jet• Is in general good agreement with experiment

Single plane data can be difficult to interpret

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Close

Thank you for your attention!Any questions?