燃料設計手法による噴霧燃焼過程の人為的制御の可能性

(1)

燃料設計手法による噴霧燃焼過程の人為的制御の可能性

著者（英） Jiro Senda 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 1‑26

year 2006‑01‑14

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

URL http://doi.org/10.14988/re.2017.0000015748

(2)

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

Jiro SENDA

Spray & Combustion Science Lab.

in Mechanical Engineering Dept.

< http://comb.doshisha.ac.jp >

Director of Energy Conversion Research Center

< http://www1.doshisha.ac.jp/~ene-cent/ >

Doshisha University, Kyoto JAPAN

2006.0.14

「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動向」

燃料設計手法による噴霧燃焼過程の人為的制御の可能性

これまでの関連の講演

（１）同志社大学エネルギー変換研究センター第２回技術セミナー国際セミナー「エンジンシステムの燃焼過程」（2004.5.28）

Fuel Design Approach for Low Emission Spray Combustion”

（２）SAE Fuel & Lubricants Meeting, Toulouse, France

^（ 2004.6.8 ） Panel Discussion on Compatibility Between the Strategy for Emissions Reduction and the Strategy to Reduce CO2 Emissions (SFL42)

“ Fuel Design Approach for Low Emission Spray Combustion Field”

[Contents in this talk]

Ⅰ Recent Research Trend for Lower Diesel Emission

Ⅰ-Ⅰ HCCI Combustion System

Ⅰ - Ⅱ Borderless in Gasoline Eng. and Diesel Eng.

Ⅱ Fuel Design Conceptual Study

Ⅱ -1 Proposal of Fuel Design Approach for Both Engines

Ⅱ-2 Author’s Fuel Design Approach Researches

Ⅱ-3 Future Extending Research Aspect

(3)

Ⅰ- Recent Research Trend for Lower Diesel Emission

Ⅰ - Ⅰ HCCI Combustion System

•Introduction of Several HCCI Approaches

•Possibility of HCCI Application into Diesel Engines in High Load Operation

Injection + (Suction Flow) Improve atomization

and turbulent mixing to reduce soot

Optimize temporal and spatial mixture distributions in-cylinder to reduce both soot (PM) and NO by DISC combustion

Split Injection

Pre-mixture Intake In-cylinder Injection (Fumigation, Dual-Fuel)

+

Fuel Conversion / Additive Injection

・Water Injection

・Emulsion Injection Our Fuel Design Approach Injection Rate Control

(Boot Injection, Pilot Injection)

High-Pressure Fuel Injection

Lean-Homogeneous Mixture Formation and Rapid Combustion by Early Injection or Retard Injection

Single Stage Two Stage MULDIC PREDIC

UNIBUS HiMICS

Small Orifice Nozzle +

High-Pressure Fuel Injection

New Attempts in Diesel Fuel Injection System

for Exhaust Emission Reduction

(4)

7 6 5 4 3 2 1

1000 1400 1800 2200 2600 3000 0 Temperature [K]

E q u iv a le n c e r a ti o

1%

10% 5% 15%

20%

25%

Soot

5000ppm NO

Low temp. rich combustion [Akihama et al., SAE Paper 2001-01-0655]

MK combustion [Kimura et al., SAE Paper 2001-01-0200]

500ppm HCCI

Desirable path [Kamimoto et al., SAE Paper 880423]

Diesel Combustion Scheme

In Equivalence Ratio – Temperature Map

Development in DI HCCI (1995~ )

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

(5)

MULDIC (Ref : SAE Paper 980505)

MULtiple stage DIesel Combustion :

PREDIC achieved the simultaneous reduction of NO

_X

and smoke emissions.

However, this technique can apply only to low and medium load condition. Therefore, MULDIC was developed for NO

_X

reduction at higher load condition.

Emission characteristics of MULDIC

adopted a multiple stage injection method

R.O.H.R. of MULDIC can decrease NO

_X

and smoke emissions even at high load condition

resulted in further improvement in exhaust emissions with EGR

has trade-off correlation between NO

_X

emission and fuel consumption

Heterogeneous Charge Compression Ignition (1)

(Keio Univ.)

Experiment Calculation

(Ritsumeikan Univ.) Heterogeneity of fuel distribution can achieve

more moderate heat release rate.

Heterogeneous charge has a possibility to

control the occurrence of main ignition.

(6)

(Ref : SAE Paper 2004-01-1756, Engine Research Center in U of W)

Stratification of the charge was varied 1) by retarding injection timing of DI.

2) by altering the ratio of DI fuel to the total fuel.

DI Premixed

charge

Stratified charge shows potential as a viable enhancement for HCCI combustion at the lean limit.

At the rich limit, the stratification was limited by the high pressure-rise rate and high CO and NO

_X

emissions.

Heterogeneous Charge Compression Ignition (2)

600rpm, =0.27 (rich limit) Fuel supply system

mass of direct injected fuel DI %=

total mass of fuel in the charge

600rpm, =0.15 (lean limit)

Ⅰ - Ⅱ Borderless in Gasoline Eng. and Diesel Eng.

(7)

Harmonization of Combustion Scheme in Gasoline Engine and Diesel Engine

Higher thermal efficiency and Lower emissions

1. Gasoline Engine Direct Injection for higher efficiency Diesel Engine HCCI for lower emission

just Fuel is changed

Application of Mixing Fuels or on-board reformulation FFV; Fuel sensing ?

2. Application of HCCI, HCSI, Rich-SI into one Engine (AVL)

Control of spark ignition

3. Several Variable Control in engine system

VVT ( compression ratio ), wide range EGR, higher pressure Fuel Injection, higher Boosting( T/C,S/C ), ・・・

Direct injection Port injection

point of view of high efficiency

Spark Ignition Gasoline Engine Gasoline Engine

HCCI combustion point of view of

low emission (NO

_X

, PM)

Compression Ignition Diesel Engine Diesel Engine

Direct injection

Mixture formation Homogeneous

premixed gas

Heterogeneous stratified mixture

Combustion mode Heterogeneous

diffusion combustion

Homogeneous

premixed combustion

In recent gasoline engines & diesel engines…

・ Mixture formation

・ Combustion mode

No definite boundary

Borderless in Gasoline Eng. & Diesel Eng.

(8)

Ⅱ

Fuel Design Conceptual Study

Ⅱ

-1 Proposal of Fuel Design Approach for Both Engines

1. Mixing Fuel with Liquefied CO2

2. Mixing Fuel with High and Low Volatility Fuel 3. (1) Soot Free Combustion with

Oxygenated fuels from kinetic analysis (2) Bio-Diesel Fuel research

(3) Direct-injected Hydrogen Diesel research

Use of Flash Boiling Spray

Control of Spray Evaporation Process through Two Phase Region in Liquid – Vapor Equilibrium in Mixing Fuels

① Mixing Fuel of Liquefied CO2 and n-Tridecane(gas oil) simultaneous reduction both Soot and NOx

② Mixing Fuel of Gas or Gasoline Component and Gas oil Component control both evaporation and ignition

Future Study in Fuel Control

① Fuel Conversion by Sono-Chemistry

② Conversion of Heavy Fuels or Solid Fuels into high quality Lighter Liquid Fuels through Chemical-Thermodynamic

Fuel Design Approach Researches with Focusing

Artificial Control of Spray Atomization and Evaporation

Artificial control of Spray

Evaporation Process

(9)

Flash Boiling Injection Process What is Flash Boiling Spray ?

Analytical model of flash boiling spray in this study

Vapor formation process

1 l

b

d Nucleation process

Bubble growth process

Droplet formation process

(1) By cavitation bubbles growth

3 3

1

4

cb

3

v n n

dM ρ N R R

(3) By superheated degree

l st

fg sh sh

T T A dt dM h

α

Droplet number = 2×Bubble number

bubble bubble liquid

V

V V

^max

2

1 3 R P

^W

P

^r

RR && & r

3 0 0

2

0

n

W V r

P P P R

R R

1

2

2 4 R 4 R

R R R

& &

and

Initial bubble diameter 2R

₀

2R

₀

=20mm

12

=1.11×10 exp -5.28

0

N T

-4.34exp -5

10

^t

a f

fg ht ht

T T A dt dM h

α

(2) Owing to heat transfer

Modeling of Flash Boiling Spray

(10)

Atomization & Evaporation in Pressure atomizer

Time & Spatial delay depending on P

_inj

,

_a

, T

_a

① Breakup delay of spray

tb

P_inj

Pr c Re Nu

② Evaporation of droplets

t A T T q

T_sat

t q T A t

Nu 2 Re Pr

Nu c 28.65 0

( )

l b

a inj a

t d

P P

③ Evaporation length of spray

P_inj L_ev

2

f f f

m& d U

tan( / 2)

a a f f

m& d x U

SMD

P_inj P 2

① ③

R

Nozzle

internal flow

Turbulence flow

②

Aerodynamical Process : disturbance

⇒

ligament

⇒

droplets

Cavity

saturation

Atomization & Evaporation in Flash Boiling Spray

Non Time & Spatial delay depending on Two Phase profile( P

_bv

( )) 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-Plesset Eq.

³ ² ¹( )

2 ^w ^r

RR&& R& P P

n

R& Pbv

Vapor mass fraction

t 1.0

Order of μ

s~ms

P_bv

200 s 100 s R

t s

Liquid jet or film Breakup by Bubbles growth

P

_bv

P

T Multi-Component

P

_bv

T P

Single Component

Breakup time

(11)

Proposal on Fuel Design Approach Research

Spray and Combustion Science Laboratory, Doshisha University

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process (4) Control the Fuel Transportation Properties in Mixing Fuels

(5) Effective liquefaction of gaseous and solid fuels

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

Proposal on Fuel Design Approach Research

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process (4) Control the Fuel Transportation Properties in Mixing Fuels

(5) Effective liquefaction of gaseous and solid fuels

Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

(12)

Two Phase Region Formation in Multi-component Fuel in Phase Change Process

Temperature

P re ss u re

Sa tu ra te d va po r l in e Sa tu ra te d

liq ui d lin e

Critical pressure Critical point Liquid phase region

Vapor phase region 0

p c

T c Critical temperature

T w o ph as e re gi on

Low Vapor Pressure Component Mixed in

High Vapor Pressure Component

Pressure-temperature diagram Pressure-Mole fraction diagram

P re ss u re [ kP a]

0 0.25 0.5 0.75 1

Liquid

Vapor Vapor mole fraction

of high vapor pressure

Vapor mole fraction of low vapor pressure

Two phase region Liquid Vapor

Mole fraction

Gas Fuel Gasoline Gas Oil Fuel Oil CO ₂

Phase 2

Phase 1

Phase 2 Gasoline Gaseous Fuel

Gas Oil Fuel Oil

CO ₂ Gas Oil

High Volatility Fuel Low Volatility Fuel

Fuel Combination for Fuel Design

(13)

Chemical Thermodynamics and Two-Phase Region

0.2 0.1 0.4 0.5 0.6 0.7 0.8 0.9 0.95

1.0 0.0 0.99

Conditions 0.3 at injection to cylinder

Ambient conditions in Diesel Engine Mole fraction of CO

₂

: X

_CO2

Conditions

inside nozzle

100 200 300 400 500 600 700 800

Fuel temperature T

_f

[K]

0 10 20 30

F u el p re ss u re p

f

[M P a]

P-T Diagram for Mixing Fuel with Liquefied CO ₂ & n-tridecane Estimation of Two-Phase Region

Expanded Corresponding State Principle

r

/

C

P P P , T

_r

T T /

_C

Peng-Robinson

Equation of States ( )

( ) ( )

RT a T

P V b V V b b V b

Fugacity of Liquid & Gas /( )

G G

i

f

i

y P

i

,

_i^L

f

_i^L

/( X P

_i

)

G L

i i

f f

The prediction of Two-Phase Region

Proposal on Fuel Design Approach Research

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process (4) Control the Fuel Transportation Properties in Mixing Fuels

(5) Effective liquefaction of gaseous and solid fuels

Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

(14)

Ignition delay of mixing fuel of C 5 H 12 with C 13 H 28

and single component fuel (Experiments)

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

Ig n it io n d el a y τ [m s]

0.75 1.75

0.5 1.0 1.25

1.5 0.0 0.25 0.5 0.75 1.0

Ignition Delay of Mixing Fuel

of i-Octane & n-Tridecane (Experiments)

X_iC8=0.0 XiC8=0.5 XiC8=0.75 XiC8=1.0

Mole fraction of i-octane X

_iC8

800K 850K 900K 950K

1000K 1050K 1100K

Ambient temperature

0 0.25 0.5 0.75 1 5

4 3 2 1 0

0.8 1.0 1.5

Ambient temperature (1000/T

_a

) [1/K]

0.9 1.1 1.2 1.3 1.4

1.0 0.1 8.0

Ig n it io n d el a y τ [m s]

1200 1100 1000 900 800 700T_a[K]

(15)

Spray Evaporation Experiments in Mixing Fuel of n-Pentane & n-Tridecane

n-C

₅

H

₁₂

: boiling point 309.3 K

n-C

₁₃

H

₂₈

: boiling point 508.7 K X

_C5H12

: Mixing fraction of C

₅

H

₁₂

Mixing Fuel and LIF Tracer Two-Phase Region in P-T diagram

X

_C5H12

V

_C5H12

Acetone

[vol.%]

Tetraline [vol.%]

1.0 1.0

5 - 0.75 0.59 2.8 2.7 0.5 0.32

1.5 4.6 0.25 0.14 0.6 5.9 0.0 0.0 - 7

X

_C5H12

: Mole fraction of n-pentane V

_C5H12

: Volume fraction of n-pentane

Acetone : C

₅

H

₁₂

Tracer Tetraline : C

₁₃

H

₂₈

Tracer

200 300 400

500 600 700 Fuel temperature T

_f

[K]

0.0 1.0 2.0 3.0 4.0

F u el p re ss u re p

f

[M P a]

Condition inside nozzle

X

_C5H12

=0.0 X

_C5H12

=0.25 X

_C5H12

=0.50 X

_C5H12

=0.75 X

_C5H12

=1.0

Comparison of Spray Structure

–Vapor Spatial Distribution–

with Experiments and Numerical Results at t=3.0ms

0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100

A x ia l d is ta n ce f ro m n o zz le t ip [ m m ]

X

_C5H12

= 0.25

X

_C5H12

= 0.50

X

_C5H12

= 0.75

7.44e-4 6.69e-4 5.95e-4 5.21e-4 4.46e-4 3.72e-4 2.98e-4 2.23e-4 1.49e-4 7.44e-5 0.00

Vapor C5 [g/cm3]

6.99e-4 6.29e-4 5.60e-4 4.90e-4 4.20e-4 3.50e-4 2.80e-4 2.10e-4 1.40e-4 6.99e-5 0.00

Vapor C13 [g/cm3]

Intensity of LIF High

High Low

Low C13

C5

left : LIF image Middle : calculation

(n-pentane) right : calculation

(n-tridecane)

C5 C13

LIF Calculation

(16)

Temporal Changes in Vapor Mass for C 5 & C 13

Mixing Fuel KIVA Analysis

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

V ap o r m as s o f n -p en ta n e [m g ]

X_C5H12=0.25 X_C5H12=0.5 X_C5H12=0.75 X_C5H12=1.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

V ap o r m as s o f n -t ri d ec an e [m g ]

X_C5H12=0.0 X_C5H12=0.25 X_C5H12=0.5 X_C5H12=0.75

Time after

injection start [ms]

n-Pentane

n-Tridecane

Multi-component Fuel Spray Behavior in Diesel Combustion Chamber

The chemical & physical properties of n-paraffin Hydrocarbon

Carbon Number in Hydrocarbon

Gas Kerosene

Gas Oil Fuel Oil Ceta ne N umb er (I gnita bility )

Octane Num ber Gasoline

low high

Mole cula r We ight Visc osity Satu rated Tem p.

Low er va por f ormi ng ra te

Lower boiling point fuel (gasoline) higher evaporation

higher octane number = poor ignitability Higher boiling point fuel (gas oil)

lower evaporation

higher cetane number = high ignitability Lower b.p fuel

Higher b.p fuel overlap region

Piston

Our Fuel Design Concept Research

･

stratified fuel vapor distribution

･

ignition at the middle part of the spray balance of physical and chemical

･

Disc shaped chamber is selected

reasonably through fuel physical

and chemical properties

(17)

Possibility in coupling of Physical Control and Chemical Control for Spray Combustion

1 By using the Mixing Fuel of Higher Boiling Point Fuels (gas oil, etc) and Lower Boiling Point Fuels (gas fuel or Gasoline, etc)

1.Lower B.P. fuel could promote the evaporation through the formation of Two Phase Region

Spatial overlap vapor distribution in the chamber 2.Higher B.P.fuel could assist the ignition

and Higher B.P. fuel could burn out the lower ignitability fuel such as Lower B.P. fuel

Proposal on Fuel Design Approach Research

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process

(4) Control the Fuel Transportation Properties in Mixing Fuels (5) Effective liquefaction of gaseous and solid fuels

Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

(18)

Proposal on Fuel Design Approach Research

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process (4) Control the Fuel Transportation Properties in Mixing Fuels

Optimization of specific heat, viscosity ,etc (5) Effective liquefaction of gaseous and solid fuels

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

Proposal on Fuel Design Approach Research

(1) Physical Control = Capability of Time and Spatial Control on Fuel Vapor Distribution by Formation of Two Phase region in Mixing Fuel Formation of Flash Boiling Spray Improvement of Spray Evaporation (2) 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)

HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

High Spray Atomization and Evaporation Quality with Flashing Process (4) Control the Fuel Transportation Properties in Mixing Fuels

(5) Effective liquefaction of gaseous and solid fuels

Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

(19)

2.As a Future study

Conversion of Heavy Fuels or Solid Fuels into high quality Lighter Liquid Fuels through Chemical-Thermodynamics with assisting by Sono-Chemistry Process

Effective usage of fossil energy resources

(5) Effective liquefaction of gaseous and solid fuels

1.Possible application for Gas Fueled Engines and Transportation Liquefied Pressure of Gas Fuels can be reduced by mixing

the higher boiling point fuel through the Two Phase Region ( It means saturated vapor pressure is reduced )

Safety of compressed gas bomb or liquefied gas bomb

Longer driving distance in CNG or LNG engine transportation

Ⅱ

Fuel Design Conceptual Study

Ⅱ

-2 Author’s Fuel Design Approach Researches

①

Mixing Fuel of Liquefied CO2 and n-Tridecane(gas oil) simultaneous reduction both Soot and NOx

②

Mixing Fuel of Gas or Gasoline Component and Gas oil

Component to control both evaporation and ignition

(20)

Combustion Experiments in CO ² & n-Tridecane Mixing Fuel

Experimental conditions

Equivalent crank speed 200 [rpm]

Water jacket temperature 353 [K]

Compression ratio 15

Injection nozzle dimension dn=0.18 [mm]

ln/dn=4.17

Injection pressure 16 [MPa]

Injection timing 5.0 ± 0.5

[deg.CA.BTDC]

Excess-air ratio 25

Ambient temperature at injection 750 [K]

Ambient pressure at injection 3.2 [MPa]

Initial cylinder pressure 0.1 [MPa]

Injection quantity (n-tridecane + CO

2

)

10.0 + 0.0 [mg]

X

CO2

=0.0

10.0 + 1.6 [mg]

X

CO2

=0.4

10.0 + 3.6 [mg]

X

CO2

=0.6

10.0 + 9.5 [mg]

X

CO2

=0.8

P-T Diagram for Mixed Fuel in RCEM

Scenario of Low Emission Diesel Combustion by Mixing Fuel Injection of Liquid CO

²

& n-Tridecane (gas oil)

1.Low injection pressure to improve efficiency 2.Improvement of spray atomization

&

Formation of vaporizing spray to form lean & homogeneous mixture

3. Control of combustion processes to reduce both NO and soot

NO reduction

(2) Thermal dissociation of CO

2

(2CO

2

⇒ 2CO+O

2

)

(3) Improvement of spray atomization and vaporization due to CO

2

separation and flashing Soot reduction

(1) Soot formation

･avoid the fuel rich mixture (2) Soot oxidation & re-burning

･Dissociation of CO

2

into CO and O

･Boudouard reaction C+CO

2

⇒ 2CO

Concept

Low Emission Scenario

Lower Flame Temperature by

(1) Latent heat of CO2 flashing

(21)

Combustion Characteristics of CO 2 /C ¹³ Mixing Fuel

Low pressure injection Improve the Thermal Efficiency Flash boiling spray

by CO 2 component Promotion of Spray Evaporation

Spray internal EGR Reduction of NOx

0

50

100 1.00 1.33 1.67 2.00 3.00 5.00 6.33 7.67 10.30 X

_CO2

=0.0

X

_CO2

=0.8

Time after injection [ms]

0

50

100 N O c o n ce n tr at io n [p .p .m .]

Bosch smoke [%]

10 20 30 40 50 60

5 10 15 20 25

X

_CO2

=0.0

X

_CO2

=0.6 X

_CO2

=0.8

Combustion Characteristics of CO 2 /C 13 Mixing Fuel

Cylinder pressure [MPa] Rate of heat release [J/deg.]

Total heat release [J]

Crank angle [deg. CA ATDC]

Gas temperature [K]

600 650 700 750 800 850

Needle lift

-20 0 20 40 60

1.0 2.0 3.0 4.0 3.5

2.5

1.5

0 50 100 150 200 250 300 350

-20 -15 -10 -5 0 5 10 15 20

X

_CO2

=0.0 X

_CO2

=0.6

X

_CO2

=0.8 Break through the trade off relation between NO and smoke

by use of liquefied CO

2

mixing fuel

(22)

0.5 0 0.1 0.2 0.3 0.4

250 300 350 400 450 500

P re s s u re [ M P a ]

Temperature [K]

C 13

C 5

C 5 /C 13

① ② ④ ⑤

Two-phase region

③

Ambient condition Experimental Conditions for Heated up Mixing Spray

310K 320K

340K

380K

440K

0.167 0.389 0.611 0.833 1.055 1.278 1.500 1.722 300

320

340

380 440 F u e l te m p e ra tu re T

f

[K ]

Time after injection start t [ms]

r

_a

= 0.765 kg/m

³

P

_inj

= 15 MPa P

_a

= 0.1 MPa T

_a

= 440 K W/O Flash Boiling

With Flash Boiling

Shadowgraph Images of Flashing Spray of C 5 /C 13 Fuels

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Combustion Experimental Conditions and Emission Results in C ⁵ & C ¹³ Mixing Fuel

X_C5H12=0.0 X_C5H12=0.25 X_C5H12=0.50 XC5H12=0.75

0 6 12 18 24 30 36 42

80 100 120 140 160 180 200 220 240 NO_X[ppm]

Smoke [%]

0%Load

20%Load 40%Load

60%Load

Engine speed [rpm] 3600

Engine load [%] 0, 20, 40, 60

Operating condition

Injection condition

Injection pressure [MPa] 15MPa Injection nozzle (n– d) 4- 0.21

Injection timing [deg.C.A.BTDC] 12 Test fuel

XC5H12=0.0 , 0.25 0.50 , 0.75 n-C₅H₁₂+ n-C₁₃H₂₈(C5/C13)

200 300 400 500 600 700

Pressure [MPa]

0 2 4 6 8 10

Temperature [K]

C13 XLPG=0.8

Two-phase region

Ambient condition

Combustion Experiments – Conditions and P-T diagram for LPG & C ¹³ Mixing Fuel with Fuel Temperature

Engine speed [rpm] 3600

Engine load [%] 60

Operating condition

Injection condition

Injection pressure [MPa] 15MPa Injection nozzle (n– d) 4- 0.21

Injection timing [deg.C.A.BTDC] 12.5 Test fuel

XLPG=0.8 LPG + n-C₁₃H₂₈(LPG/C13)

Tf = 310 370 410 440 K

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Emissions and Engine Performance (Mixing of LPG/C 13 )

With Flash Boiling W/O Flash Boiling

1.4

0.6 0.8 1.0 1.2

NO_Xi/NO_X310[A.U.]

1.4

0.6 0.8 1.0 1.2

0.4 Smokei/Smoke310[A.U.]

300 320 340 360 380 400

THC [ppmC]

12.5 13.0 13.5 14.0 14.5 15.0

BSEC [MJ/kWh]

300 320 340 360 380 400 420 440 Initial fuel temperature [K]

W/O flash boiling With flash boiling

T_f=410

T_f=310 T_f=370 T_f=440

(a) THC Emission and Engine Performance (b) Relation between Smoke and NO

_X

Ⅱ

Fuel Design Conceptual Study

Ⅱ

-3 Future Extending Research Aspect 1. Application of Fuel Design Approach into

HCCI engines for Lower Emissions and Ignition Control

2. Coupling of Fuel Design Approach with

Combustion Chamber Geometry Design

(25)

HCCI Application of Fuel Design Approach

< HCCI Engines >

•Advanced fuel Injection Lower Ta & Pb

•Ignition control is required Ignition improver Some additives

•Importance in Spatial Vapor Distribution Homogeneity or Heterogeneity ?

< Fitting of Mixing Fuels to HCCI >

*Possibility of Flashing Spray due to lower Ta & Pb

*Mixing Additives can control the Ignition Process

*Controllability of Spatial Vapor Distribution due to the Two Phase Region Profile

Finally,

We are intending to couple Fuel Design Process - Two Phase Region Profile -

with Combustion Chamber Geometry Design considering Fuel Spray Evaporation Process

Artificial Control to optimize the Fuel Spray

Evaporation Process for each Engine Chambers

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Optimization of Spray Evaporation Process and Chamber Geometry by adjusting Two Phase Profile of the Fuel

Formation of Shorter Spray Spray should be penetrated to near the chamber wall where air mass is enough HC and PM should be reduced by avoiding the spray and wall interaction

Optimization of Two Phase Region Profile Selection of Mixing Fuels Mixing Fraction

T P

High B.P.Fuel Low B.P.

Fuel

Formation of Longer Spray

Small Engines

Large Engines Combustion

Combustion

Doshisha University

君は神を見たか！？

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

君は神を見たか！？

Could you catch up

a finger print of the God!?

(27)

燃料設計手法による噴霧燃焼過程の人為的制御の可 能性