Engine Fuel Overview and Fuel Design Approaches for Diesel Spray Combustion

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Engine Fuel Overview and Fuel Design Approaches for Diesel Spray Combustion

著者（英） Jiro Senda

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 1‑33

year 2007‑12‑05

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

URL http://doi.org/10.14988/re.2017.0000015671

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

Jiro SENDA

Spray & Combustion Science Lab.

Doshisha University, Kyoto JAPAN

Engine Fuel Overview and Fuel Design

Approaches for Diesel Spray Combustion

International Seminar on Recent Trend of Fuel Research for Next – Generation Clean Engines (2007.12.5)

<contents>

Ⅰ Overview of Engine Fuels

Ⅱ Recent Diesel Engine Combustion Scheme

Ⅲ Our Fuel Design Approach Researches

Ⅳ Summary

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Japan’s New National Energy Strategy

By courtesy of Mr. M. Nakada (JSAE/Technoba)

“ Future Fuel Scenario in Japan ”

(10th Int. Conf. on Present and Future Engines for Automobiles)

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Future Fuel Scenario in Japan

By courtesy of Mr. M. Nakada (JSAE/Technoba)

“ Future Fuel Scenario in Japan ”

(10th Int. Conf. on Present and Future Engines for Automobiles)

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Ⅰ Overview of Engine Fuels

■ Current Crude Petroleum Oil ÆGasoline, Diesel Oils ( Light oil & Heavy Oil )

# shift to high quality oil Æ surplus of A class Heavy Oil and Life Cycle Oil

# demand to reduce the dependency of fossil fuel up to 80% by 2030 in transportation in Japan

current petroleum fuels Æ Alternative Fuels

■ Liquid Fuels < XTL = Synthetic Oil >

# Another Fossil Resources Æ Liquefied resources --- < GTL & CTL >

ÆGas to Liquid ( FTD oil, DME etc) , Coal to Liquid

# Biomass -- < BTL >

Æ Ethanol / ETBE & Bio Diesel Fuel (BDF) (Hydrogenated Bio Diesel)

■ Gaseous Fuels

# Natural Gas ( CH4)

# Hydrogen, Hydrogen/CH4 (Hythane)

Æ Application for both Fuel Cell (FC) and Engines – Which is major ?

Æ Optimum Hydrogen Energy Application is depending on H2 production

procedure or path , thermal efficiency in the power unit

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Considerable points

■ Well to Tank analysis for current fossil resources

Natural Gas Æ GTL: Gas to Liquid ( FTD / DME) Coal Æ CTL: Coal to Liquid

# Fuel production way with CO2 minimum

# Resources amount ?

■ Renewable Fuels ; BTL: Biomass to Liquid (Ethanol & BDF) Ethanol blend Gasoline / ETBE blend Gasoline ( 3 % in Japan ) Neat BDF / BDF blend Diesel Gas Oil (B20 et. al) ( 5 % in Japan )

# nearly carbon neutral but global warming gas free ?

# How is energy density / resources amounts / small production capacity ? generation process: from 1

^st

=based on food crop to 2

^nd

= based on biomass

■ Fuel Diversity for Engines Æ Flexible Fuel Engine

Æ Engine modification or Engine adaptation

■ On-Board Reformulation of Fuels

Æ need to On-Board Fuel Sensing

( Chemical and Physical Fuel Properties)

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GTL Researches in Japan

■ Researches on FTD and DME in Japan

# AIST- National Institute of Advanced Industrial Science and Technology

# JARI – Japan Automobile Research Institute

# LEVO – Low Emission Vehicle Organization &

NTSEL – National Traffic Safety and Environment Laboratory (2001-)

# Several Automotive Makers

■ FTD Performance (ref.SAE-2007-01-2004 by Toyota)

# Lower Density, Higher Heating Value, Lower Sulfur, Lower Aromatic Species ( High Cetane Index )

# Lower PM, HC,CO & Equal NOx

# Non problem in Fuel Supply and Injection Equipment

■ DME Performance ( general view & LEVO Project )

# Lower Sulfur, Lower Aromatic, Oxygenated Fuel, Volatile Property, Lower Viscosity

# Lower NOx, HC,CO & PM Free

# Problem of Cavitation and Erosion/Abrasion in Fuel Supply and Injection Equipment

■ Engine Modification for FTD & DME

# Load reduction of DPF by Lower PM

# NOx Reduction by EGR and NOx Catalyst

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BDF research

■ Fuel Property – Ex. RME (Rapeseed Methyl Ester)

# Oxygenated Fuel, Similar Cetane Number, Sulfur free, Aromatic free

# High Boiling Point, Unstable in Oxidation for Liquid State

# Lower Potential in Low Temperature Properties such as

CFCP(Cold Filter Clogging Point), CFPP(Cold Start Filter Plugging Point)

■ General engine performance

① Soot or PM is reduced remarkably, but SOF slightly increases in light load conditions

② Few emissions in SOx

③ NOx is almost same or slightly increasing.

④ CO and HC are depending on the fuel properties or engine

operating conditions.

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Candidates for Alternative Fuels

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Ⅱ Recent Diesel Engine Combustion Scheme

Recent Research Trend

# New Attempts in Diesel Fuel Injection System for Exhaust Emission Reduction

# Introduction of Several HCCI Approaches

ÆPossibility of HCCI Application into Diesel Engines in High Load Operation

Borderless in Gasoline Engine and Diesel

Engine

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BACKGROUND - New Attempts in Diesel Fuel

Injection System for Exhaust Emission Reduction

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

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Progress in 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

HCCI

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

Ref) Kitamura, T. et al.,

Int. J. Engine Res., 2002 HCCI combustion

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

_x

emissions.

In direct injection system…

to realize HCCI combustion,

injection timing has to be advanced.

However, in diesel engine…

gas oil causes wall-wetting and poor mixture preparation owing to the low volatility.

Therefore…

The other lean combustion concepts

where Injection timings are set close to

TDC have been proposed in diesel engine.

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Importance of Fuel in Engine Systems

■ Borderless situation in Gasoline Engine and Diesel Engines

• Harmonization of Combustion Scheme in Gasoline Engine and Diesel Engine

for Higher thermal efficiency and Lower emissions

# Direct injection has been applied to Gasoline engines to

improve the thermal efficiency. And, homogeneous charge is introduced into Diesel engines as HCCI system to reduce NOx emission.

# From the point of both mixture formation and basic

combustion mode, we have no definite boundary for these engines, in another words, we are in the stage of borderless situation in both engines.

■ Engine design from the Fuel properties

# To improve thermal efficiency and exhaust emissions

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Engine Control and Fuels in Current Engines - Fuel Sensing for the Future FFV System?

■ Several Variable Control in engine system

Æ VVT ( compression ratio ), wide range EGR, Higher Pressure Multiple Fuel Injection, higher Boosting( T/C,S/C ), ・・・

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

Æ Control of spark ignition

■ Æ Application of Mixing Fuels or on-board reformulation ?

■ Æ FFV; Fuel sensing ?

■ Several Variable Control in engine system Æ VVT(Valve-toronich, Valvematic,VVEL)Æ

Variable Compress. ratio Wide Range EGR,

Higher Pressure Multiple Fuel Injection,

Higher Boosting( T/C(VGT),S/C )ÆEngine Down Sizing

■ Application of HCCI, HCSI, Rich-SI into one Engine

Æ Control of spark ignition

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Development of SI – CI Hybrid Engines in 2007

HCCI Gasoline Engines

(1) Starting ~ Very Light Load = SI Operation (up to 1000 rpm) (2) Light Load = HCCI Operation (1000 ~ 3000 rpm)

without a throttle restriction

Æ Higher Efficiency & Lower NOx (Low Temp. Combustion)

(3) Higher Load = SI Operation (3000 rpm ~ wide open throttle)

General Motors – Saturn Aura

# 2.2-L Ecotec 4-cylinder engine

# 4 key technology enablers – direct multiple injection, 2-step valve lift, electric phasing of the intake and exhaust camshaft

Mercedes Benz – DiesOtto

# 1.8-L 4-cylinder engine ; 238ps / 400Nm, 6 ℓ /100km

# 7 key technological features

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Ⅲ Our Fuel Design Approach Researches

① Mixing Fuel of Liquefied CO2 and n-Tridecane(gas oil)

Æ for simultaneous reduction both Soot and NOx

② Mixing Fuel of Gas or Gasoline Component and Gas oil Component

Æ to control both evaporation and ignition

③ Application into HCCI(PCCI) Combustion Mode

Æ to control vapor heterogeneity and mixture ignition

④ Mixing Fuel of Bio-Diesel Fuel and Lower Boiling Point Hydrocarbon Fuel

Æ to improve fuel distillation and the viscosity

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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 Æ Formation of Flash Boiling Spray ÆImprovement of Spray Evaporation (2) Chemical Control = Capability of Control on Combustion Process

Æ Emission Control – Soot & NOx

Simultaneous reduction of both Soot and NOx (CO2-gas oil mixing fuel) Æ Ignition Control (Gasoline-gas oil mixing fuel)

Æ HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

Æ 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

Æ Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

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What is Flash Boiling Spray ?

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

Temperature

Pressure Sa tu ra ted

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 Two

ph as e reg

ion

Low Vapor Pressure Component Mixed in

High Vapor Pressure Component

Pressure-temperature diagram Pressure-Mole fraction diagram

Pressure [kPa]

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

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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 Æ Formation of Flash Boiling Spray ÆImprovement of Spray Evaporation

(2) Chemical Control = Capability of Control on Combustion Process Æ Emission Control – Soot & NOx

Simultaneous reduction of both Soot and NOx (CO2-gas oil mixing fuel) Æ Ignition Control (Gasoline-gas oil mixing fuel)

Æ HC Control (Gasoline-gas oil mixing fuel)

(3) Improving Thermal Efficiency by Lower Injection Pressure

Æ 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

Æ Conversion of Heavy Fuels or Solid Fuels into high quality

Lighter Liquid Fuels through Chemical-Thermodynamics

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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

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

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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

Axial distance from nozzle tip [mm]

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

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① Scenario of Low Emission Diesel Combustion by Mixing Fuel Injection of Liquid CO2 & 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

Low Emission Scenario

Lower Flame Temperature by (1) Latent heat of CO2 flashing

Concept

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Spray and Flame Structure of

CO ² /C 13 Mixing Fuel in RCEM

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

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Combustion Characteristics of

CO ² /C 13 Mixing Fuel in RCEM

NO concentration [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

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

Total heat release [J]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

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

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0.5 0 0.1 0.2 0.3 0.4

250 300 350 400 450 500

Temperature [K]

C 13

C 5

C 5 /C 13

① ② ④ ⑤

Two-phase region

③

Ambient condition

② Experimental Conditions for Heated up C5/C13 Mixing Spray

310K

320K

340K

380K

440K

Pressure [MPa]

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Shadowgraph Images of Flashing Spray of C5/C13 Mixing Fuels in RCEM

300

320

340

380 440 Fuel temperature T

f

[K]

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

0.167 0.389 0.611 0.833 1.055 1.278 1.500 1.722

Time after injection start t [ms]

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Combustion Experimental Conditions and

Emission Results in C 5 & C 13 Mixing Fuel in Engine

X_C5H12=0.0 X_C5H12=0.25 X_C5H12=0.50 X_C5H12=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–φ d) 4-φ 0.21

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

X_C5H12=0.0 , 0.25 0.50 , 0.75 n-C₅H₁₂+ n-C₁₃H₂₈(C5/C13)

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④ Mixing Fuel of Bio-Diesel Fuel and Lower Boiling Point Hydrocarbon Fuel

B100 BDF-A BDF-B BDF-C BDF-D Density(288K) [g/cm³]

Kinetic viscosity(313K) [mm²/s]

CFPP [K]

Cloud point [K]

Pour point [K]

0.8861 0.8291 0.7810 0.7287 0.7345 4.614 2.622 1.495 0.853 0.959

268 258 253 239 243

269 266 266 252 243

235 250 245 240 240

T10 [K] 606-616 446 378.5 372 373

T50 [K] 609-619 606 498.5 391.5 391.5

T90 [K] 628-641 614.5 611.5 511 516

Gas oil JIS No.2 0.835

2.70

264-271 - 260 488-498 548-558 605-618 B100

BDF-A BDF-B

B100 C₁₂H₂₆

C₇H₁₆ or i-C₈H₁₈*

1 1

1

6 3

1

1 0

0

BDF-C

BDF-D 6* 3 1

1 3

6

Composition of Test Fuels and Their Properties

Volume ratio

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Distillation Curve of each Fuel Tested

20 80 100

40 Distillation ratio [%]

0 60

650 350 400 450 500 550 600

Distillation temperature [K]

B100

BDF-A

BDF-B

BDF-C

BDF-D

Gas oil

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Effect of Oxygen Content in Fuel on Soot Formation

1000

800

600 400 0 8 10 12

Oxygen content in fuel [mass%]

Averaged LII signal intensity [-]

2 4 6

TASI/T

_inj.

=0.8 Gas oil

BDF-D

BDF-C BDF-B

BDF-A B100

Tamb.=900K, Pinj.=74.1MPa

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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

Small Engines

Selection of Mixing Fuels Mixing Fraction

T P

High B.P.Fuel Low B.P.

Fuel

Formation of Longer Spray

Large Engines Combustion

Combustion

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Ⅳ Summary - 1

External Factors

1. Emission Regulation – Tier Ⅱ Bin 5(EPA), Euro 4 ÆEuro 5(EU)

2005 Standards Æ Proposed 2009 standards (JP) 2. Lower Fuel Consumption (Higher Thermal Efficiency)

( Ex. CO2 emission 140g/km in vehicle (EU), CAFE (UA)) 3. Fuel Diversity for Engines Æ Flexible Fuel Engine

(Å exhaustion of crude petroleum oil & reduction of fossil fuel dependency) For the Small Engines

For the Small Engines ( for mainly Diesel Engines ) ( for mainly Diesel Engines ) 1. Fuel Application

# Synthetic Oil Application from another fossil resources (GTL(FTD ･ DME)) will be getting major

# 2nd generation based on biomass - Cellulose ( Ethanol / ETBE / BDF ) will be one candidate as the blended fuels

# Several Mixing Fuels with Current Crude Petroleum Oil & GTL/BTL should be focused to improve spray and combustion phases in engines

< This is our Fuel Design Concept >

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Ⅳ Summary - 2

Thank you for your kind attention

2. Combustion Mode

# HCCI ( PCCI ), Multi-Stage HCCI, MK( Modulated Kinetics ) should be applied as the optimized operation mode (lower load) to reduce emissions

# These several combustion modes are very sensitive to fuel properties ( Direct injected spray evaporation & Ignition )

# These modes might be extended to higher load operation assisted by several variable control systems (VVT, EGR, Injection Control, Higher Boosting) and application of several mixing fuels

# In higher load operation, Low Temp. Rich Combustion or Conventional Rich Spray Diffusion Burning should be applied, with after-treatment device of oxidation catalyst, DPF and NOx catalyst ( LNT/SCR ) ( it cause fuel penalty )