Auto-Ignited Kernels during Knocking Combustion

in a Spark-Ignition Engine

Okayama University Nobuyuki KAWAHARA Eiji TOMITA

End-gasEnd-gas320 340 360 380 400

0.0

1.0

2.0

3.0

4.0

Crank angle, deg.

Pre

ssu

re,

MP

a Knocking cycle

Standard cycle

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Background

Requirements of spark-ignition (SI) engine - Lower fuel consumption - Reduced emission of pollutants.

Higher thermal efficiencies

Engine knocking due to higher compression ratio

Heater

Out

Mixturetank

Thermocouple

SolenoidValve-closure signal

Elongated piston

Electric motor

FlywheelTDC signalCrank angle pulse

Rotary encoder

Pressure transducer

ValveValve-stopper

WaterIn

Spark electrode

Bore: 78 mmStroke: 85 mmCompression ratio: 9.02Engine speed: 600 rpm

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Compression-expansion engine

Bore: 78 mmStroke: 85 mmCompression ratio: 9.0Engine speed: 600 rpm

180

Crank angle, deg.

210 240 270 300 330 360(TDC)(BDC)

Side viewTop view

Timing chartValve closing Ignition

In

Water Out Burned gasUnburned gas

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Compression-expansion engine

Knock intensity: KInt

H.P.F2.5kHz

360 380 4000

1

2

3

4

Pre

ssu

re,

MP

a

Inte

nsi

ty,

MP

aCrank angle, deg.

0 0.005 0.01 0.015-0.4-0.2

00.20.4

Time from ignition, s

KInt

0 5 10 15Time from ignition, ms

Experimental condition

Fuel (Octane number)Equivalence ratio, φ Initial pressure, P0

Spark ignition timing, θIT　　

n-C4H10 (94)1.0

40, 50, 60kPa335～ 355deg.

H2

1.040kPa

335～ 360deg.

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Experimental condition

Use of Ar&O2 mixture instead of air

Mirror

Flywheel

Electric motor

PC

Cassegrain　 optics

Pressure Transducer

Valve

CylinderMeasurementpoint

Spark electrode

Experimental methods

Shimadzu Hyper vision, HPV-1Nac Image Technology, MEMRECAM GX1

High-speed video camera

320 340 360 380 400

Pre

ssu

re,

MP

a

Crank angle, deg.320 340 360 380 400

0.0

1.0

2.0

3.0

4.0

320 340 360 380 400

P0=50kPaΘIT=350deg. P0=60kPaΘIT=340deg. P0=60kPaΘIT=345deg.

Standard cycle KInt=0.434MPa

n-Butane(Φ=1.0) Rec.Speed:32kf.p.s Rec.Expose:1/8

KInt=0.180MPa

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Knock image (n-Butane)

P0=50kPaIT=350deg.

P0=60kPaIT=345deg.

Normal cycle

Knocking cycle

A B C D E F G

a b c d e f g

Flame frontAuto-ignited kernel

350 360 370 3800

1

2

3

4

Pre

ssu

re, M

Pa

Crank angle, deg.350 360 370 3800

1

2

3

4

A B C D E F G H I

361 362 363 3642.5

3.0

3.5

4.0

Pre

ssu

re, M

Pa

Crank angle, deg.

350 355 360 365 3700

1.0

2.0

3.0

4.0

Rec.speed:63kfps

KInt=0.491MPa

360.0deg. ～366.4deg.

Φ=1.0 P0=60kPa,ΘIT=345deg.

A

B

C

E F G H ID

B Flame front

Auto-ignitedkernel

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Knock image and pressure history (n-Butane)

A B C D E F G H I

361 362 363 3642.5

3.0

3.5

4.0

Pre

ssu

re, M

Pa

Crank angle, deg.

350 355 360 365 3700

1.0

2.0

3.0

4.0

Rec.speed:64kfps

360.0deg. ～366.4deg.

Φ=1.0 P0=60kPa,ΘIT=345deg.

A

B

C

D E F G H I

KInt=0.491MPa

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Knock image and pressure history (n-Butane)

320 340 360 380 400 420 320 340 360 380 400 420

= 1.0 , P0=60kPa , T0=323K , Rec.speed : 20kfps.

Crank angle , deg. Crank angle , deg. Crank angle , deg.

Pre

ssur

e ,

MP

a

C4H10 , ΘIT=345deg.

Kint=0.07MPa

C4H10 , ΘIT=360deg.

Non-knock condition

CH4 , ΘIT=340deg.

Non-knock condition

320 340 360 380 400 420

4

3

2

1

0

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Knock image and pressure history (n-Butane)

0

1

2

3

360 365 370 375 380

Pre

ssu

re, M

Pa

Normal cycle

Crank angle, deg.

H2-Air 　　 φ=1.0 P0=60kPa T0=323K θi=360deg.

Kint=0.03MPa

1

2

3

375 380

Knocking cycle

0360 365 370

Crank angle, deg.

H2-O2-Ar φ=1.0 P0=40kPa T0=323K θi=360deg.

Kint=1.53MPa

Compared normal cycle with knocking cycle

Rec. speed=60,000fps Rec. speed=60,000fps

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Pressure wave

Auto-ignition

0

1

2

3

330 340 350 360 370

CA, deg.

Pre

ssu

re, M

Pa

H2-O2-Ar φ=1.0 θi=340deg. Rec. speed=250,000fps Exposure time=2s Kint=0.99MPa

Knocking cycle

Visualization of pressure wave and estimation of the frequency

1

1.5

2

345 345.5 346 346.5

CA, deg.

Pre

ssu

re, M

Pa

136s

A1

A2B1

B2

Frequency=7.35kHz

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