Control of PCCI Combustion Using Physical and Chemical Characteristics of Mixed Fuel

Control of PCCI Combustion Using Physical and Chemical Characteristics of Mixed Fuel

著者（英） Yoshimitsu Wada journal or

publication title

国際セミナー「次世代クリーンエンジンのための燃 料研究の最新動向」

page range 1‑34

year 2007‑12‑05

権利（英） Research Center for Energy Conversion System of Doshisha University

URL http://doi.org/10.14988/re.2017.0000015668

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Doshisha Univ. - Energy Conversion Research Center

International Seminar on Recent Trend of Fuel Research for Next-Generation Clean Engines

Control of PCCI Combustion using Physical and Chemical

Characteristics of Mixed Fuel

Doshisha Univ. – Energy Conversion Research Center Postdoctoral fellow Yoshimitsu WADA

December 5th, 2007

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Progress in CI Engine Combustion

*n-heptane, reaction time=1ms 7

6 5 4 3 2 1

1000 1400 1800 2200 2600 3000 0 Temperature [K]

Equiv a lence ratio [-]

1%

10% 15% 5%

20%

25%

Soot

5000ppm

NO

Low temp. rich combustion

PCCI

MULDIC and MK combustion 500ppm D es ira bl e pat h

Ref) Kitamura, T. et al.,

Int. J. Engine Res., 2002 PCCI combustion

has the potential to be highly efficient and to produce low PM and NO

emissions.

However, diesel fuel…

having low volatility, causes wall-wetting and poor mixture preparation.

In addition,

well-mixed mixture ignites simultaneously

and the operation is limited by the steep

pressure rise.

Effect of Charge Heterogeneity on PCCI Combustion

Ref) Kumano, K. and Iida N., SAE Paper 2004-01-1902

Steep combustion of HCCI

is mitigated by employing

charge heterogeneity

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Effect of Charge Heterogeneity on PCCI Combustion

Experimental results

Ref) Sjöberg, M. and Dec, J. E., SAE Paper 2006-01-0629

Computational results using CHEMKIN-Z

* Therefore, partial fuel-stratification is effective for fuels exhibiting two-stage ignition (LTR and HTR), such as gas oil.

Staged combustion event is achieved

by employing partial fuel-stratification

because the timing of hot ignition is

sensitive to local φ .

☺ Partial fuel-stratification is effective to reduce maximum pressure rise rate due to staged combustion event !

Staged combustion event is achieved by fuels exhibiting two-stage ignition (LTR and HTR) !

However . . .

☹ Fuels exhibiting two-stage ignition such as diesel fuel have low volatility…

How can we get fuels having high ignitability and

high volatility ??

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Ignition Characteristics of Mixed Fuel

Rapid Compression and

Expansion Machine P

=15MPa ρ

=17.8kg/m

T

=750K

Single component fuel

Mixed fuel of n-C ₁₃ H ₂₈ / n-C ₅ H ₁₂

Mole fraction of n-Pentane

13 11 9 7 5

Carbon number

Ignition delay τ [ms]

0.75 1.75

0.5 1.0 1.25 1.5

0.0 0.25 0.5 0.75 1.0

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Pressure-Temperature Diagram of Mixed Fuel

Two Phase Region

High B.P.

Component Low B.P.

Component

Liquid Phase

Super Critical Region

Temperature

Pressure

Dew point curve Bubble point curve

Gas Phase Mixed Solution

Mixed Solution

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Flash Boiling Phenomena

Nozzle internal flow

∆ T

Atomization Bubble growth = Evaporation

Temperature

Pressure

P

∆ T

Temperature

Pressure

P

∆ T

Advantage of Flash Boiling for Early Timing Injections

Crank angle

Fuel condition In-cylinder condition

∆ T

∆ T

∆ T

Pressure

Temperature

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Test fuel :

n-tridecane + i-pentane T _f =310K 345K 380K 410K

1.75 1.5 1.25 1.0 0.75 0.5 0.25 0.0

Pressure [MPa]

320 360 400 440 480

Temperature [K]

X _iC5 =0.8 X _iC5 =1.0

X _iC5 =0.0 435K

∆ ^T _bub

( ) _a

bub f

bub T T p

T = −

∆

Ambient and Fuel Conditions, plotted on P-T diagram

of Mixed Fuel

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Superheating from bubble point ∆ T

[K]

T

310K 345K 380K 410K 435K 50

40

30

20

θ Spray cone angle [degree]

10

-90 -60 -30 0 30 60 90 120

θ

= θ

’+ θ

”

=

A

’ A

”

θ

θ

A

’ A

”

0 to 2mm

nozzle spray

d

Measured Spray Cone Angle

as a Function of ∆T _bub ⁽ P _inj =50MPa, d _n =0.20mm)

Spray Images for each Superheating from Bubble Point ( T _a = 445K, ρ _a =2.0kg/m ³ , P _inj =50MPa, d _n =0.20mm)

T

=310K T

=345K T

=380K T

=410K T

=435K 0

45

90 22.5

67.5

Ax ial distance from nozzle tip [mm]

-30.7 4.3 39.3 69.3 94.3

∆ T

[deg.] =

Time after Corrected Start of Injection:0.45ms

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Experimental Setup

Resistance thermometer AVL 415S

Charge amplifier

Surge tank

Rotary encoder

Electric Heater Injector MEXA-1500D

Pressure transducer

Dynamometer

Surge tank

Laminar flow meter

Dehumidified air PC

Heated hose

Engine Common rail

Supply pump

EDU

ECU

Doshisha University

-20 -15

-10 -5 TDC 5 Crank angle

[deg. CA. ATDC]

180 150 120 90 60 30 0 Apparent heat release rate [J/deg.]

T

=310K, ∆ T

= -30.7K T

=345K, ∆ T

= 4.3K T

=380K, ∆ T

= 39.3K T

=410K, ∆ T

= 69.3K φ =0.30, ε =13

θ

=-80deg.CA ATDC

150 120 90 60 30 0 Apparent heat release rate [J/deg.]

θ

=-70deg.CA ATDC θ

=-80deg.CA ATDC

θ

=-90deg.CA ATDC θ

=-100deg.CA ATDC

φ =0.30, T

=410K, ε =13

Effect of Superheating Degree and Injection Timings on Combustion Phasing (Included Spray Angle = 60deg.)

Higher superheating degree Early ignition

Earlier injection timings

late ignition

Experimental Condition for the Case of Single Injection

Fuel n-C

H

+ i-C

H

(X

=0.8)

Injection pressure [MPa] 50.0

Effective equivalence ratio φ

[-] 0.41

Nozzle hole diameter [mm] 0.20 (L

/d

= 4) 310, 410

Bore × Stroke 100 × 106

Cooling System water cooled (353K)

Fuel injection system direct injection (common-rail)

[mm]

Compression ratio [-] 10.0 : 1

Intake temperature [K] varied

Fuel temperature T

[K]

Number of holes 4

50% burned crank angle 5.5

[deg. CA ATDC] (adjusted by intake air temperature)

Included spray angle [deg.] 100

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Experimental Condition for the Case of Single Injection

Fuel n-C

H

+ i-C

H

(X

=0.8)

Injection pressure [MPa] 50.0

Effective equivalence ratio φ

[-] 0.41

Nozzle hole diameter [mm] 0.20 (L

/d

= 4)

Fuel temperature T

[K] 310, 410

Bore × Stroke [mm] 100 × 106

Cooling System water cooled (353K)

Fuel injection system direct injection (common-rail)

Compression ratio [-] 10.0 : 1

Number of holes 4

Intake temperature [K] varied

50% burned crank angle 5.5

[deg. CA ATDC] (adjusted by intake air temperature) φ

: Effective equivalence ratio calculated

from effective injection quantity Q

Q

: Injection quantity calculated from

carbon balance method

Included spray angle [deg.] 100

300

Temperature [K]

330 360 390 420 450

1.0

0.8

0.6

0.4

0.2

0

Pressure [MPa]

T _f =310K T _f =410K

Start of injection [BTDC]

55deg.CA 60deg.CA 70deg.CA 80deg.CA 90deg.CA 100deg.CA

Relation among Two-Phase Region, In-Cylinder Pressure

and Fuel Temperature

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Combustion and Emissions Characteristics (Single Inj.)

18

-100 -90 -80 -70 -60 -50

Injection timing θ

[deg.CA ATDC]

15 12 9 6 3 0 Amount of wall-wetting fuel [%]

10 8 6 4

8 6 4 2

Fuel carbon into THC [%] 0 Fuel carbon into CO [%]

0 0.25 0.5 0.75

NO

[g/g

]

Spray images at 80deg.CA BTDC

Axial distance from nozzl e exit [mm]

0

15 7.5

T

=310K ( ∆ T

= -30.7deg.)

T

=410K

( ∆ T

= 69.3deg.) -60

-70 -80

-90 -100

Injection timing θ

[deg.CA ATDC]

400 350 300

Intake temp. [K] T

=310K (W/O flash boiling)

T

=410K (W/ flash boiling)

Combustion and Emissions Characteristics (Single Inj.)

18

-100 -90 -80 -70 -60 -50

Injection timing θ [deg.CA ATDC]

15 12 9 6 3 0 Amount of wall-wetting fuel [%]

10 8 6 4

8 6 4 2

Fuel carbon into THC [%] 0 Fuel carbon into CO [%]

0 0.25 0.5 0.75

NO

[g/g

]

Spray images at 80deg.CA BTDC

Axial distance from nozzl e exit [mm]

0

15 7.5

T

=310K ( ∆ T = -30.7deg.)

T

=410K

( ∆ T = 69.3deg.) -60

-70 -80

-90 -100

Injection timing θ

[deg.CA ATDC]

400 350 300

Intake temp. [K] T

=310K (W/O flash boiling)

T

=410K (W/ flash boiling)

inj real

inj eff inj

real wet

wall

Q

Q Q Q

,

,

,

−

−

=

Q

: Measured injection quantity

Q

: Injection quantity calculated from

carbon balance method

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Experimental Condition for the Case of Two-Stage Injection

Fuel n-C

H

+ i-C

H

(X

=0.8)

Injection pressure [MPa] 50.0

Total supplied energy [J] 1335

Nozzle hole diameter [mm] 0.20 (L

/d

= 4) 410

Compression ratio 10.0 : 1

Fuel temperature T

[K]

[-]

Number of holes 4

Intake temperature [K] 307

50% burned crank angle

[deg. CA ATDC]

3.75

(adjusted by EGR ratio) 1st injection timing [deg.CA ATDC] -80

( φ =0.43 without EGR)

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

30 20 10 0 200 150 100 50

0.4 0.5 0.6 0.7 EGR ratio [%] NO

[ppm] Maximum pressure rise rate [ M Pa/deg.]

-50 -40 -30 -20 -10

2nd injection timing θ [deg.CA BTDC]

1st injection only

1st injection only (NO

)

1st injection only

0.09 0.06 0.03 0

Smok e [FSN]

Combustion and Emissions Characteristics ( θ _inj,1st =-80deg.CA ATDC, Q _inj,2nd =30%)

θ

is out-of-control

after θ

= -10deg.

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

30 20 10 0 200 150 100 50

0.4 0.5 0.6 0.7 EGR ratio [%] NO

[ppm] Maximum pressure rise rate [ M Pa/deg.]

-50 -40 -30 -20 -10

2nd injection timing θ

[deg.CA BTDC]

1st injection only

1st injection only (NO

)

1st injection only

0.09 0.06 0.03 0

Smok e [FSN]

Combustion and Emissions Characteristics ( θ _inj,1st =-80deg.CA ATDC, Q _inj,2nd =30%)

θ

is out-of-control after θ

= -10deg.

Rich

early ignition more NO

Lean

late ignition

less NO

Combustion and Emissions Characteristics

( θ _inj,1st =-80deg.CA ATDC, θ _inj,2nd =-20deg.CA ATDC)

30 20 10 0 200 150 100 50

0.4 0.5 0.6 0.7

1st injection only

1st injection only EGR ratio [%] NO

[ppm]

Maximum rate of pressure rise [M Pa/deg.]

10 20 30 40 50

Percentage of 2nd injection quantity [%]

1st injection only (NO

)

0.09 0.06 0.03 0

Smok e [FSN]

-15 -10 TDC 10 Crank angle [deg.CA ATDC]

200

150

100

50

Apparent heat release rate [J/deg.] 0

-5 5 15

Q

=30%

Q

=10%

Q

=20%

Q

=40%

Q

=50%

Histories of Apparent Heat Release Rate

( θ _inj,1st =-80deg.CA ATDC, θ _inj,2nd =-20deg.CA ATDC)

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Combustion and Emissions Characteristics

( θ _inj,1st =-80deg.CA ATDC, θ _inj,2nd =-20deg.CA ATDC)

1st injection only

99 96 93

1st injection only

10 20 30 40 50

Percentage of 2nd injection quantity [%]

Combustion efficiency [%]

3 2 Fuel carbon into THC [%] 1

3 2 Fuel carbon into CO [%] 1

1st injection only

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Combustion and Emissions Characteristics

( θ _inj,1st =-80deg.CA ATDC, θ _inj,2nd =-20deg.CA ATDC)

1st injection only

99 96 93

1st injection only

10 20 30 40 50

Percentage of 2nd injection quantity [%]

Combustion efficiency [%]

3 2 Fuel carbon into THC [%] 1

3 2 Fuel carbon into CO [%] 1

1st injection only

Reduction in 1st injection quantity

more HC, CO

less HC, CO

Reduction in 1st injection quantity

Rich less CO

Lean

more CO

Contents

Background

9

Combustion Control Methodology using Mixed Fuel

9

- simultaneous pursuit of high ignitability and high volatility - mixture formation control taking into account

two-phase region

Spray Characteristics of Mixed Fuel

9

Combustion Characteristics of Mixed Fuel in CI Engine

9

Conclusions

9

Doshisha University – Energy Conversion Research Center & Spray and Combustion Science Laboratory –

Conclusions

The flashing spray of mixed fuel is effective to reduce the amount of wall-wetting fuel, THC and CO emissions for early fuel injection.

Mixed fuel consisting of high and low carbon number fuels exhibits active low temperature oxidation reaction and thus, this character makes it possible to mitigate the steep combustion.

By choosing optimum ignitability of high carbon number fuel while keeping low temperature oxidation reactivity, further improvement of thermal efficiency would be achieved.

(because compression ratio is set at 10 in this study)

The multiple injection combined with flash boiling spray has

a possibility of decreasing in both maximum pressure rise

rate and NO _X concentration.

Thank you for your kind attentions