燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

(1)

燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

著者（英） Yoshimitsu Wada journal or

publication title

第7回技術セミナー「燃料・燃焼制御によるディーゼル燃焼の低エミッション化の研究動向」

page range 1‑24

year 2006‑01‑14

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

URL http://doi.org/10.14988/re.2017.0000015749

(2)

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

学術フロンティア「次世代ゼロエミッション・エネルギー変換システム」

技術セミナー

燃料・燃焼制御によるディーゼル燃焼の低エミッション化の研究動向

燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

同志社大学大学院噴霧・燃焼工学研究室和田好充

Motivation

Homogeneous Charge Compression Ignition Benefits (potential)

Challenges

fuel-flexibility

high thermal efficiency reduction of NO

_X

emission reduction of PM emission

controlling ignition timing over a range of speeds and loads

7 6 5 4 3 2 1

1000 1400 1800 2200 2600 30000 Temperature [K]

Equivalence ratio [-]

1%10%5%15%

20%

25%

Soot

500ppm NO HCCI

500ppm

(fuel: n-heptane, p=6MPa, reaction time: t=2ms) Ref) 北村ほか(同志社大学)

第17回内燃機関シンポジウム

extending the operating range

- stretching out the heat-release event - promoting the ignition

mitigating hydrocarbon and

carbon monoxide emissions

(3)

with high swirl, high EGR and retarded injection timing

MK (NISSAN)

UNIBUS (TOYOTA)

with dividing fuel injection into two stages in order to enable rapid combustion at low temperatures

with two side injectors in order to avoid collision of the spray with cylinder wall

PREDIC (New ACE)

Ref: SAE Paper 1999-01-3681

HiMICS (HINO)

with multiple injection system early stage inj., pilot inj., main inj., late stage inj.

Ref: SAE Paper 961163

Development in DI HCCI

Introduction of Recent HCCI Approach -1- Ref.) 島崎，西村 (いすゞ中央研究所)

第17回内燃機関シンポジウム

Injection near top dead center High pressure fuel injection Small orifice diameter Low cetane number fuel or exhaust gas recirculation

(4)

Introduction of Recent HCCI Approach -2-

First Injection

Second Injection

Ref.) G, A. Lechner et al. (Univ. of Michigan) SAE Paper 2005-01-0167

for example –cone angles of 80 or 60deg.

about the vertical centerline

<Using Narrow Spray Cone Angle Nozzle>

Injection timing

(Early injection + Injection near TDC)

Port Injection Direct Injection

均一な予混合気の形成が可能予混合気が不均一着火・燃焼過程が燃料の化学反応

に律則

着火・燃焼過程が燃料の分布形態により制御可能

混合気の質により人為的な燃焼制御が可能

混合気形成過程など物理的制御が困難

Purpose

人為的な介入は予め決定される化学反応特性と燃焼までの物理過程のみ！

(5)

Proposal on Fuel Design Approach

Chemical Control= Capability of Control on Combustion Process Emission control –Soot & NOx

simultaneous reduction of both soot and NOx (CO2-gas oil mixing fuel) Ignition control (Gasoline-gas oil mixing fuel)

Unburned HC control (Gasoline-gas oil mixing fuel) Physical Control= Capability of Time and Spatial Control

on Fuel Vapor Distribution

Use of Flash Boiling Spray

improvement of spray atomization and evaporation Formation of Two-Phase Region in Mixing Fuel improvement of evaporation on Low Volatility Fuel

Modification of Fuel= Control of Fuel Transport Properties

= Effective Liquefaction of Gaseous and Solid Fuels Fuel Conversion by Sono-Chemistry

Conversion of Heavy Fuels or Solid Fuels into high quality Liquid Fuels through Chemical-Thermodynamic

Evaporation Characteristics of Mixed Fuel based on Pressure-Temperature Diagram

Two Phase Region

High B.P.

Component Low B.P.

Component Liquid Phase

Super Critical Region

Temperature

Pressure

Saturated Vapor Line

Saturated Liquid Line

Gas Phase Mixed Solution Mixed Solution

(6)

bubble ligament

droplets intact core

※Evaporation due to Enthalpy balance of fuels without aerodynamic force

Bubble Nucleation rate

Evaporation rate = Bubble growth Rate exp A N C

k 4 2

A 3 R

Rayleigh-PlessetEq. ³ ² ¹( )

2 ^w ^r

RR&& R& P P

n

R& Pbv

Vapor mass fraction

t 1.0

Order of μs~ms ^Pbv

200 s 100 s R

s t

Liquid jet or film Breakup by Bubbles growth

P_bv P

T Multi-Component

P_bv

T P

Single Component

Breakup time

Atomization & Evaporation in Flashing Spray

Engine Specifications and Experimental Conditions

Engine type DI Diesel,single cylinder, water cooled 4 stroke cycle,2 valves

Bore×Stroke [mm] 110×106

Compression ratio [-] 16.3 , 14.0

Combustion chamber Dish

Fuel injection system Common-rail

Nozzle configuration 0.14×8（Angle 60deg.）

Fuel (n-C₇H₁₆/i-C₈H₁₈mixture) PRF0, 20, 40, 60, 80

Engine speed [rpm] 1200

Injection pressure [MPa] 72

Intake temperature [K] 303

Intake relative humidity [%] 35

Injection timing [deg. BTDC] -100, -90, -80, -70, -60, -50, -40

Equivalence ratio [-] varied

(7)

Charge amplifier

F-V converter

Surge tank Surge

tank

Laminar flow meter

Dry and wet bulb hygrometer

Air conditioner Resistance

temperature sensor Rotary encoder

Supply pomp Coolant flow system Engine

Dynamometer

PC

Common rail Thermo couple

MEXA 1500D Smoke meter

Heater

330cc×20 times

Schematic Diagram of Experimental Setup for Engine Test

THC NO_X CO CO₂

0.10 0.35 0.30 0.25 0.20 Equivalence ratio 0.15

0.45 0.40

0.05 -100 -90 -80 -70 -60 -50 -40 Injection timing [deg. CA ATDC]

-30 -110

misfire or knocking untried burn

=14.0 =16.3

※COV of IMEP : Coefficient Of Variation of IMEP

Operating Range Tested

COV of IMEP < 10% and dP/d < 1.0MPa

(8)

Effect of Injection Timing and

Ignitability on

Exhaust Concentration

100 90 80 70 60 50 40

Injection timing [deg. CA. BTDC]

0.2 0.8 0.6 0.4

CO [%]

3000 2500 2000 1500 THC [ppmC]1000

300 200 100 0

NOx[ppm]

= 14.0

= 0.24 PRF0 PRF20 PRF40 PRF60 : An Example

250 200 150 100 50 0

NOx[ppm]

450 375 300 225 150 75 0

NOx[ppm]

PRF0 PRF20 PRF40 PRF60 PRF80

300 400 500 600 700 800 900 1000 300 400 500 600 700 800 900 1000 Cumulative heat release [J] Cumulative heat release [J]

CA_inj= 50deg. BTDC CA_inj= 70deg. BTDC

NOx Concentration as a Function of Cumulative Heat Release ( =14.0)

low er ig

nitab ility

low er ig

nitab ility

(9)

NOx Concentration as a Function of Maximum In-Cylinder Temperature ( =14.0)

400 350 300 250 200 150 100 50 0

NOx[ppm]

975 1050 1125 1200 1275 1350

Maximum in-cylinder temperature (mean) [K]

CA_inj=50deg. BTDC

CA_inj=70deg. BTDC

CA_inj=80deg. BTDC CA_inj=40deg. BTDC

0 20 40 60 80

Apparent Heat Release RateQ[J/deg.]

0 5 10 15 20

-5 -10 -15

Crank angle [deg. ATDC]

Centroid of H.T.H.R.

Definition of Heat Release Centroid during H.T.H.R.

CA CA CA CA CA

Q

(10)

Combustion Efficiency vs. Heat Release Centroid

-12 -9 -6 -3 TDC 3 6 9 12

Crank angle of heat release centroid [deg. C.A. ATDC]

=14.0

=16.3 50

100 90 80 70 60 50 100 90 80 70 60

Combustion efficiency [%]Combustion efficiency [%]

Degree of Constant Volume vs. Heat Release Centroid

Crank angle of heat release centroid [deg. C.A. ATDC]

-12 -9 -6 -3 TDC 3 6 9 12

=14.0

=16.3 1.0

0.99 0.98 0.97 1.0 0.99 0.98 0.97 0.96

Degree of Constant Volume [-]

(11)

Doshisha UniversityCrank angle of heat release centroid-12–Energy Conversion Research Center & Spray and Combustion Science Laboratory –-9 -6 -3 TDC 3 6[deg. C.A. ATDC]9 12

=14.0

=16.3

Indicated Thermal Efficiency vs. Heat Release Centroid

0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.45 0.40 0.35 0.30 0.25 0.20 0.15

Indicated thermal efficiency [-]

0 450 400 350 300 250 200 150 100 50

NOx[ppm] NOx[ppm]

75 80 85 90 95 75 80 85 90 95

Combustion efficiency [%] Combustion efficiency [%]

=14.0 =16.3

Relation between NOx Concentration and Combustion Efficiency

=0.29

=0.27

=0.17

=0.18

=0.22

=0.24

=0.27

=0.17

=0.18

=0.22

=0.13

(12)

-100 -90 -80 -70 -60 -50 -40

Injection timing [deg. CA ATDC]

-100 -90 -80 -70 -60 -50 -40 0.10

0.35

0.30

0.25

0.20

0.15

IMEP [MPa]

=14.0 =16.3

PRF0 PRF60

Condition : Combustion Efficiency > 85 %

Successful Operating Conditions in Our Range Tested

Tentative Summary

Thermal Efficiency

NOx

Oparating Range

Ignitability Heterogeneity

Deg. of constant volume

Combustion efficiency

Mean temp. Local temp.

Nozzle configuration

Misfire

Opt.

Knocking ？

※Comparison with Gas Oil

(13)

Gasoline

LPG DME

GTL Bio diesel fuel

Gas oil

Natural gas

Bio ethanol

Kerosene

Heavy oil

ignitability

b o ili n g p o in t, d e n s it y , v is c o s it y

high low

highlow

Lower Carbon Number Higher Carbon Number

Summary of Conventional and Alternative Fuel relating to Physical and Chemical Characteristics

Nozzle hole diameter Orifice pressure drop Injection quantity Injection equipment

0.20 50.0 22.2 Common-rail type [mm]

[MPa]

[mg]

Ambient temperature Ambient density

[K]

[kg/m³] Ambient pressure [MPa]

Ambient gas

Simulated crank angle

[deg.BTDC] 100 80 60 40

N₂

0.17 0.26 0.44 0.93 Fuel temperature T_f [K]

1.5 2.0 3.0 5.2

(L_n/d_n= 4)

625 515

445 405

310, 345, 380, 410, 435

Experimental Conditions in case of Chamber Test

(14)

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

BTDC 80deg.

BTDC 60deg.

BTDC 40deg.

BTDC 100deg.

435K

Experimental Conditions Plotted on Pressure-Temperature Diagram

Spray angle1[degree]

T_f 310K 345K 380K 410K 435K

-1.5 -1.0 -0.5 0 0.5 1.0

0 50 40 30

20 10

Pressure difference P [MPa]

Spray Cone Angle Measured near Nozzle Exit

( 0 to 2mm from Nozzle Exit)

(15)

Double-convex lens (f=1000mm)

Ar^＋ Laser (λ=488nm) Plano-convex lens (f=40mm)

ND filter

Pin hole Pin hole

Double-convex lens (f=1000mm)

High speed camera Frame rate=20,000f.p.s.

Exposure time=2 s

Optical Setup for Schlieren Photography

T_f=310K T_f=380K T_f=410K T_f=435K

P=0.16 P=-0.37 P=-0.83 P=-1.35

T_f=345K P=-0.02 0

45

90 22.5

67.5

Axial distance from nozzle tip [mm]

Schlieren Images for each Initial Fuel Temperature

Simulated Crank Angle = 80deg.BTDC

(16)

T_f=310K T_f=345K T_f=380K T_f=410K T_f=435K

Temporal Change in Spray Tip Penetration for each Initial Fuel Temperature

90 75 60 45 30 15 0

BTDC80deg. BTDC60deg.

Axial distance from nozzle tip [mm]

0 0.15 0.3 0.45 0.6 0.75 0.9 Time after corrected start of injection [ms]

P=0.15MPa P=-0.03MPa P=-0.37MPa P=-0.84MPa P=-1.36MPa BTDC80deg.

P=0.33MPa P=0.15MPa P=-0.19MPa P=-0.65MPa P=-1.18MPa BTDC60deg.

0 1 2 3 4

Time after start of injection [ms]

0 20 15 10 Spray angle [degree] 5

0 1 2 3 4

Time after start of injection [ms]

Temporal Change in Spray Dispersion Angle for each Initial Fuel Temperature

T_f=310K T_f=345K T_f=380K T_f=410K T_f=435K P=0.15MPa P=-0.03MPa P=-0.37MPa P=-0.84MPa P=-1.36MPa BTDC80deg.

P=0.33MPa P=0.15MPa P=-0.19MPa P=-0.65MPa P=-1.18MPa BTDC60deg.

(17)

Engine Specifications and Experimental Conditions

Engine type DI Diesel,single cylinder, water cooled 4 stroke cycle,2 valves

Bore×Stroke [mm] 110×106

Compression ratio [-] 14.0

Combustion chamber Dish

Fuel injection system Common-rail

Nozzle configuration 0.198×4（Angle 60deg.）

Fuel n-C₁₃H₂₈/ i-C₅H₁₂(X_iC5=0.8)

Engine speed [rpm] 1200

Injection pressure [MPa] 50

Intake temperature [K] 303

Intake relative humidity [%] 35

Initial fuel temperature [K] 310, 345, 380, 410 Injection timing [deg. BTDC] -100, -90, -80, -70, -60, -55

Equivalence ratio [-] 0.30

An Example of Apparent Heat Release Rate (BTDC 80deg.)

-20 -15 -10 -5 TDC 5 10

0 100 80 60 40 20

Apparent heat release rate [J/deg.]

1200 1100 1000 900 800 700 600

In-cylinder temperature [K]

T_f=310K T_f=345K T_f=380K T_f=410K

(18)

Crank Angle and Temp. when LTHR and HTHR Start

-100 -90 -80 -70 -60 -55

Injection timing [deg. ATDC]

-2 -4 -6 -8 -10 -12 -14 -15 -16 -17 -18 -19

800 700 600 500

900 800 700 600

In-cylinder temperature [K]

T_f=310K T_f=345K T_f=380K T_f=410K

LTHR

HTHR

2%

3%

4%

10%

9%

10%

Total Hydrocarbon Emission as a Function of P

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 4000

3500 3000 2500 2000 1500 1000 500 0

Pressure difference P [MPa]

Total Hydrocarbon [ppmC]

BTDC 100deg.

BTDC 90deg.

BTDC 80deg.

BTDC 70deg.

BTDC 60deg.

BTDC 55deg.

Injection timing

(19)

NO

_X

Concentration vs. Maximum In-Cylinder Temperature

1100 1150 1200 1250 1300 1350

Maximum In-cylinder temperature (mean) [K]

0 500 400 300 200 100 NOx[ppm]

T_f=310K T_f=345K T_f=380K T_f=410K

Conclusion (1)

燃料の着火性は各機関条件に対し燃焼時期を決定する役割がある．

低負荷時における混合気の過度な希薄化は燃焼効率の悪化を招く．

ただし，混合気の不均一性はNOxの排出と深い関わりがあり，

その排出量により燃焼効率ひいては熱効率が制限される．

噴射量の増加に伴い，低NOxを維持したまま燃焼効率を向上できる範囲が広がる．

燃料の着火性と混合気の不均一性により運転可能な負荷範囲が規定される．

比較的遅い噴射時期では燃料の着火性が混合気の不均一性に影響を及ぼす．

(20)

Conclusion (2)

早期燃料噴射時の低圧雰囲気条件下では低沸点成分を混合した2成分混合燃料を用いることで，容易に減圧沸騰噴霧が得られる．

雰囲気条件と過熱度（減圧度）の適切な組み合わせにより，早期筒内噴射式予混合圧縮着火機関の未燃排出成分は抑制可能である．

減圧沸騰による噴霧性状の改善は高沸点成分のピストン表面への燃料付着に起因する黒煙の排出を改善する．

減圧沸騰の適用により，高い燃焼効率でも低NOx化の可能性がある．

(21)

均一な予混合気の形成が可能予混合気が不均一着火・燃焼過程が燃料の化学反応

に律則

着火・燃焼過程が燃料の分布形態により制御可能

燃料噴霧の質により人為的な燃焼制御が可能

混合気形成過程など物理的制御が困難

Port Injection Direct Injection

Fuel-Supply Systems in HCCI Operation

NOx Concentration as a Function of Maximum In-Cylinder Temperature ( =14.0)

400 350 300 250 200 150 100 50 0

NOx[ppm]

975 1050 1125 1200 1275 1350

(22)

975 1050 1125 1200 1275 1350

400 350 300 250 200 150 100 50 0

NOx[ppm]

NOx Concentration as a Function of Maximum In-Cylinder Temperature ( =14.0)

CA_inj=50deg. BTDC

CA_inj=70deg. BTDC

70 75 80 85 90 95 70 75 80 85 90 95

0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10

=14.0 =16.3

IMEP [MPa] IMEP [MPa]

90 92 94 96 98

0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10

=14.0 =16.3

IMEP [MPa] IMEP [MPa]

90 92 94 96 98

IMEP vs. Combustion Efficiency for each Octane Number

(23)

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 Pressure difference P [MPa]

7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5

BTDC 100deg.

BTDC 90deg.

BTDC 80deg.

BTDC 70deg.

BTDC 60deg.

BTDC 55deg.

Injection timing

Period from Start of HTHR to its Centroid for each P

Period from start of HTHR to its Centroid[deg. C.A.]

Period from Start of HTHR to its Centroid as a Function of Combustion Efficiency

0.75 0.80 0.85 0.9 0.95 1.0

Combustion efficiency [-]

8 7 6 5 4 3 2 1

Period from start of HTHR to its Centroid[deg. C.A.] T_f=310K T_f=345K T_f=380K T_f=410K

(24)

25

20

15

10

5

-0.8 -0.4 0.0 0.4 0.8

Maximum heat release rate [J/deg.]

Pressure difference ΔP[MPa]

Maximum Heat Release Rate during LTHR as a Function of Pressure Difference ΔP

Purpose

FUEL

Chemistry

Physical Property

1st step

: for early injection

2nd step

: for multiple injection

hetero geneity Ignitability

emissions combustion

spray atomization

evaporation flash boiling 燃料の物理・化学的特性がHCCI燃焼へ及ぼす影響を調べ，

その最適化法および限界を知る

(25)

Introduction of Recent HCCI Approach -3-

Ref.) Y. Ra and R. D. Reitz (ERC) SAE Paper 2005-01-0148 Variable Geometry Spray

is capable of changing the spray angle with time in various ways.

燃料の物理・化学的特性を駆使した予混合圧縮自着 火燃焼の制御

燃料の物理・化学的特性を駆使した予混合圧縮自着 火燃焼の制御

著者（英） Yoshimitsu Wada journal or

publication title

第7回技術セミナー「燃料・燃焼制御によるディー ゼル燃焼の低エミッション化の研究動向」

page range 1‑24

year 2006‑01‑14

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

URL http://doi.org/10.14988/re.2017.0000015749

燃料の物理・化学的特性を駆使した 予混合圧縮自着火燃焼の制御

同志社大学大学院 噴霧・燃焼工学研究室 和田 好充

Motivation

fuel-flexibility

high thermal efficiency reduction of NO

emission reduction of PM emission

controlling ignition timing over a range of speeds and loads

extending the operating range

- stretching out the heat-release event - promoting the ignition

mitigating hydrocarbon and

carbon monoxide emissions

MK (NISSAN)

UNIBUS (TOYOTA)

PREDIC (New ACE)

HiMICS (HINO)

Development in DI HCCI

Introduction of Recent HCCI Approach -1- Ref.) 島崎，西村 (いすゞ中央研究所)

Introduction of Recent HCCI Approach -2-

First Injection

Second Injection

Ref.) G, A. Lechner et al. (Univ. of Michigan) SAE Paper 2005-01-0167

<Using Narrow Spray Cone Angle Nozzle>

Purpose

Proposal on Fuel Design Approach

Evaporation Characteristics of Mixed Fuel based on Pressure-Temperature Diagram

Two Phase Region

Atomization & Evaporation in Flashing Spray

Engine Specifications and Experimental Conditions

Charge amplifier

F-V converter

Surge tank Surge

tank

Laminar flow meter

Dry and wet bulb hygrometer

Air conditioner Resistance

temperature sensor Rotary encoder

Supply pomp Coolant flow system Engine

Dynamometer

PC

Common rail Thermo couple

MEXA 1500D Smoke meter

Heater

Schematic Diagram of Experimental Setup for Engine Test

misfire or knocking untried burn

=14.0 =16.3

Operating Range Tested

Effect of Injection Timing and

Ignitability on

Exhaust Concentration

= 14.0

= 0.24 PRF0 PRF20 PRF40 PRF60 : An Example

NOx Concentration as a Function of Cumulative Heat Release ( =14.0)

NOx Concentration as a Function of Maximum In-Cylinder Temperature ( =14.0)

Definition of Heat Release Centroid during H.T.H.R.

Q

Q

Combustion Efficiency vs. Heat Release Centroid

Degree of Constant Volume vs. Heat Release Centroid

Indicated Thermal Efficiency vs. Heat Release Centroid

Relation between NOx Concentration and Combustion Efficiency

=14.0 =16.3

Successful Operating Conditions in Our Range Tested

Tentative Summary

Thermal Efficiency

NOx

Oparating Range

Ignitability Heterogeneity

Deg. of constant volume

Combustion efficiency

Mean temp. Local temp.

Nozzle configuration

燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

第7回技術セミナー「燃料・燃焼制御によるディーゼル燃焼の低エミッション化の研究動向」

燃料の物理・化学的特性を駆使した予混合圧縮自着火燃焼の制御

同志社大学大学院噴霧・燃焼工学研究室和田好充