cngdeisel

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Development of CNG Direct Injection Diesel-Cycle Engine

Masaki Okada*Senior Specialist, Department No. 1, Engine Design and Development, Isuzu Motors Limited.

Co-researchers: Hiroyuki Sugii and Tetsuya Wakao, Isuzu Motors limited

John Cryer, Robbie Dickson, Buerebista Ursu, Westport Innovations Inc.

Abstract

Isuzu Motors Limited (Japan) and Westport Innovations Inc. (British Columbia, Canada), with support

from the New Energy and Industrial Technology Development Organization (NEDO of Japan) and theJapan Gas Association, completed the worlds first vehicle operating test for the compressed natural gashot surface ignited direct injection (CNG-DI) diesel-cycle engine, providing the feasibility of thetechnology for commercialization.

This project entitled The Commercial Development of High-efficiency, Ultra-low Emission CNG

Vehicles, was carried out from 2001 to March 2004. Objectives of the project were 1., to improvethermal efficiency by 25%or more over the Otto cycle; and, 2., to achieve at least 75% lower emissions

than the minimum standard at the time of initial low-emission regulations (ultra-low-emission vehicles;

ULEV)

The ELF was used as the base vehicle (load capacity: 2 tons) and succeeded in achieving these

objectives. The model vehicle participated in Michelins Challenge Bibendum 2003 in California andwon Gold Awards in the emission and fuel efficiency categories, and a Silver in the vehicle noisecategory, capturing the attention of domestic and international industry watchers with its close-

to-commercialization performance. The ELF uses a 4.5-liter diesel engine as its base engine, with apower and torque of 100kw/2200rpm and 500Nm/1000rpm, respectively. In this case the engine was

equipped with a 25 MPa common-rail CNG (mono fuel) direct injection system, an on-boardcompressor, hot surface ignition system, variable nozzle turbo, a urea-SCR catalyst (NOx reduction)

and an oxidation catalyst (HC reduction) for clean emission.

In the development, Westport provided full support for the fuel supply, ignition and associated control

systems. Many special features are incorporated in the engine. The natural gas compressor was used toraise the injection pressure up to 25 MPa. The natural gas injector uses a magnetostrictive actuator.Some unique features are incorporated in the part of the ignition system. To study the combustion

process, STAR-CD and WC-ERC (the University of Wisconsin-Madison Engine Research Center)program was employed. Today we are able to accurately reproduce the actual combustion on thecomputer.

Although we have overcome significant challenges, in the future, we aim for higher specific output

engines and better customer attributes (reliability, fuel economy, noise and vibration). Here I would liketo continue to provide actual data and present the benefit of the CNG-DI diesel-cycle engine.

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1. Purpose

Isuzu Motors Limited Carried out this project with support from Westport Innovations (prototype fuel,ignition and associated control systems). Moreover, many of development expense were supported bythe New Energy and Industrial Technology Development Organization and the Japan Gas Association.

Japans transportation sector has a very strong dependence on oil, at 98%, compared to other sectors,and the growth rate for oil consumption is also high. It is crucial for Japan, an energy-importing nation,to introduce and develop alternative energies for oil. Urban air pollution problems are driving the

need and the desire for clean natural gas vehicles. The currently available natural gas vehicles,however, are not comparable to conventional diesel vehicles in fuel consumption, a fact that is a major

obstacle to their general acceptance. From the perspectives of alternative energy development, low

emission and the prevention of global warming, it is therefore an important and urgent issue to developa natural gas vehicle with fuel consumption comparable to diesel vehicles as well as ultra-low

emission.

Based on the above, our objective was to develop a high-efficiency, ultra-low emission commercialnatural gas vehicle that would be an alternative to commercial diesel vehicles.

2. Study objective

The objective was to develop an engine with the following target values and demonstrate that it can bea viable alternative through tests using an actual vehicle with the engine.

(1) To improve the engine cycle efficiency by 25% or more:

Parameter for efficiency: CO2 emission Test gas = 13A

G-13 Mode Target for this project (Note) Conventional mixer system

Average emission (g/kWh) 640 or less 800

(2) To reduce emission by 75% or more of the maximum values allowed in the emission regulation at

the time of project commencement. (meeting ultra-low-emission vehicle requirements)

Test gas = 13A

G-13 Mode NOx CO NMHC

Average emission (g/kWh) 0.85 16 0.18

3. Roadmap to the targets

3.1 Different fueling systems of CNGFig. 1 shows different types of CNG fueling systems. They are divided into two major types: Otto

cycle and Diesel cycle. In addition, there are pre-mixing before cylinder input, In-cylinder pre-mixing,and injection immediately before combustion (or during combustion). Fig.2 shows our evaluation ofthe commercial viability of each type.

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3

0

20

40

60

80

100

0 20 40 60 80 100

Engine Speed (%)

Load

(%)

Idle

1,4

2

3

5

6 7

89

10

11

1213

G13 mode (g/kWh)

Production CNG VehicleProduction CNG VehicleProduction CNG VehicleProduction CNG Vehicleemission performanceemission performanceemission performanceemission performance

InitialInitialInitialInitial

CNG vehicle emissionCNG vehicle emissionCNG vehicle emissionCNG vehicle emissionGuideline 2000Guideline 2000Guideline 2000Guideline 2000

Test gas

OperatingStability

Fuel Economy Reliability/Durability

Cost Packaging Remarks

Carburetor type -

stoichiometric8 5 8 10 9

Efficiency is not great. Can use

TWC for low emissions.

MPI Type -

stoichiometric8 5 8 9 9


TWC and has better emissions

than above.

Carburetor type -

lean 7 6 8 10 9

Improvement in efficiency, but

not as good as diesel. Stability

not has good, reliability not has

good, HC emissions can be an

Direct Injection

Type with spark

plug5 7 6 7 8

Improvement in efficiency over

all above, not as good as diesel,

not proven, lower r eliability

potential.

MPI Type with pilot 7 8 5 6 6


TWC and has better emissions

than above.

Direct injection

Type with glow plug8 10 5 5 6

Improvement in efficiency over

all above. Needs optimization.

Very good potential for

efficiency. Single fuel.

Direct Injection

Type with pilot9 10 7 5 5

May have best potential for

reliability and efficiency, more

complex, more expensive, dual

fuel.

Otto CycleOtto CycleOtto CycleOtto Cycle Diesel CycleDiesel CycleDiesel CycleDiesel Cycle

Pre-Mixed Direct Injection

Mono-Fuel

Diesel Oil Pilot Glowplug ignition

Mixer SPI/MPI GDI Dual-Fuel

Fig. 1 Various Combustion Systems for CNG Fig.2 Technical Evaluation for Each Combustion

Systems

3.2 G-13 Mode test cycle and performance of currently available engines

Fig. 3 shows the 13 operating conditions of the G-13 Mode. The sizes of circles depict the relativeweight of each condition toward the composite result. As shown, the G-13 Mode covers a fairly high

load range even though it is supposed to be focused on the low load range.

A currently mass-produced CNG engine that has been very well received in the marketplace producesapproximately 800 g/kWh of CO2. Its NOx, HC, and CO emission values are as shown in Table 1

in the G-13 Mode; it is an extremely clean engine thanks to the use of a three-way catalyst.

Fig. 3 G-13 mode: Japanese Emission Test

Conditions and Weighting

Table 1 Emission of Production CNG Engine

In order to reduce CO2 to 640 g/kWh as targeted, a 25% improvement in thermal efficiency is requiredsince (800 640)/640 = 0.75, which represents an unattainable target when using the well-known

in-cylinder direct injection Otto cycle alone. An introduction of some innovative technologies at the

same time is undoubtedly required.

3.3 Selection of combustion systems and prognosis of target achievement

From the results of a simulation study, it had been known that the suggested approach of conventionaltechnology with modifications, or stratified combustion combined with the pre-mixing in-cylinder

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S c h e m eS c h e m eS c h e m eS c h e m eG 1 3 M o d e F u e l E c o n o m yG 1 3 M o d e F u e l E c o n o m yG 1 3 M o d e F u e l E c o n o m yG 1 3 M o d e F u e l E c o n o m y

D e c r e a s e R a t i o D e c r e a s e R a t i o D e c r e a s e R a t i o D e c r e a s e R a t i o

D i s u s e T h r o t t l e V a l v eD i s u s e T h r o t t l e V a l v eD i s u s e T h r o t t l e V a l v eD i s u s e T h r o t t l e V a l v e 5555

L e a n C o m b u s t i o n = 1 . 4L e a n C o m b u s t i o n = 1 . 4L e a n C o m b u s t i o n = 1 . 4L e a n C o m b u s t i o n = 1 . 4 3333


C o m p r e s s i o n R a t i o C o m p r e s s i o n R a t i o C o m p r e s s i o n R a t i o C o m p r e s s i o n R a t i o 2222


D e c r e a s e M e c h a n i c a l L o s sD e c r e a s e M e c h a n i c a l L o s sD e c r e a s e M e c h a n i c a l L o s sD e c r e a s e M e c h a n i c a l L o s s 3333

M i l l e r C y c l eM i l l e r C y c l eM i l l e r C y c l eM i l l e r C y c l e 5555

C o m b u s t i o n I n p r o v e m e n tC o m b u s t i o n I n p r o v e m e n tC o m b u s t i o n I n p r o v e m e n tC o m b u s t i o n I n p r o v e m e n t 1 01 01 01 0

H i g h T o r q u e @ L o w r p mH i g h T o r q u e @ L o w r p mH i g h T o r q u e @ L o w r p mH i g h T o r q u e @ L o w r p m 7777

F u e l S u p p l y L o s sF u e l S u p p l y L o s sF u e l S u p p l y L o s sF u e l S u p p l y L o s s 5 5 5 5

25252525 29292929TotalTotalTotalTotal



























1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

70 90 110 130 150 170

Crank angle (deg)

LocalA/F

TDC

A/F Monitoring point

Average A/F

Start of Injection

31.0

Ignitiontiming

direct injection, would be extremely difficult to handle (refer to Fig. 4). Based on these factors and

the efficiency improvement target, we decided to choose the in-cylinder direct injection diesel cycle.Table 2 shows the components to be modified and improved to the benchmark (current levels) and theirestimated contributions to the improvement in fuel economy (CO2).

The basic approach was to modify the diesel engine combustion system to include natural gas directinjection, hot surface ignition combustion approach. This would allow the engine to retain highthermal efficiency, a hallmark of diesel engines and use Isuzus extensive and proven knowledge of

diesel-type combustion systems. If successful, it would be possible to exceed the targets by a largemargin.

The overall approach was planned in such a way that it would be possible to go back to theconventional technology with additional modifications (pre-mixing in-cylinder direct injection) at

anytime since it was still an untested and unproven technology. We also felt that a high efficiency inthe compressor pump system might become a key to success.

Table 2 Improved Items of CO2 (Fuel Economy)

and The Contribution

Fig. 4 The results of a stratified combustion

study by CFD

4. Engine development4.1 Vehicle and base engine and their target performances

Our target was to produce a vehicle performance equivalent to the currently available CNG vehicle

with a higher torque and lower engine speed for better fuel economy (CO2). Fig. 5 shows the

performance curves of the conventional CNG engine and the CNG-DI engine of this project.

Fig. 6 the vehicle performance curves. The base engine, transmission, and differential gear were

selected from the models currently commercially available so that the study could commence withoutmanufacturing special components. For durability, the target was set to fall within the range alreadyverified by the base engine.

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5

30

40

50

60

70

80

90

100

110

500 1000 1500 2000 2500 3000 3500

Engine Speed (rpm)

Power(kW)

0

100

200

300

400

500

600

Torque(Nm)

CNG-DI targetpower

CNG Base Eng.Power

CNG-DI Target

torque

CNG Base Eng.

Torque

CNG-DI Vehicle

Base CNG Vehicle

Vehicle speed (Km/h)

RunningResistance&Drivingforce

Enginespeed(rpm)

CNG-DI Vehicle

Base CNG Vehicle



Enginespeed(rpm)

CNG-DI Vehicle

Base CNG Vehicle

CNG-DI Vehicle

Base CNG Vehicle Base CNG Vehicle



Enginespeed(rpm)

CNG-DICNG-DICNG-DICNG-DI RemarkRemarkRemarkRemark

Number of cylinderNumber of cylinderNumber of cylinderNumber of cylinder In-line 4In-line 4In-line 4In-line 4

Valve systemValve systemValve systemValve system valves (InletExhaust valves (InletExhaust valves (InletExhaust valves (InletExhaust

Bore StrokeBore StrokeBore StrokeBore Stroke Same as base diesel engine

DisplacementDisplacementDisplacementDisplacement Same as base diesel engine

Air intake systemAir intake systemAir intake systemAir intake system Turbocharger with intercoolerTurbocharger with intercoolerTurbocharger with intercoolerTurbocharger with intercooler Variable nozzle

Injection systemInjection systemInjection systemInjection system Direct injectionDirect injectionDirect injectionDirect injection With fuel compressor system

Injection pressureInjection pressureInjection pressureInjection pressure MaxMPaMaxMPaMaxMPaMaxMPa Variable lift control

Combustion chamberCombustion chamberCombustion chamberCombustion chamber type type type type Same as base diesel engine

Compression ratioCompression ratioCompression ratioCompression ratio Same as base diesel engine

Ignition systemIgnition systemIgnition systemIgnition system Glow plug ignitionGlow plug ignitionGlow plug ignitionGlow plug ignition With closed shield

Swirl ratioSwirl ratioSwirl ratioSwirl ratio Same as base diesel engine

CamCamCamCam Same as diesel engineSame as diesel engineSame as diesel engineSame as diesel engine

CNG-DI VehicleCNG-DI VehicleCNG-DI VehicleCNG-DI Vehicle Base CNG VehicleBase CNG VehicleBase CNG VehicleBase CNG Vehicle

Fuel

Body type

Occupant

Maximum payload

Number of cylinder

Bore Stroke

Displacement

Air intake system Turbocharger with intercooler NA

Injection system Direct injection Gas mixerVenturi type

Compression ratio

Ignition system Glow plug ignition Spark ignition

Power

Torque

Transmission

Overall length

Overall width

Overall height

Wheel base

Tread Front

Rear

Vehicle mass

GVW

Front

Rear Tire size

Weight

Engine

Dimensions

Tilt cab

In-line 4

Fig. 5 Engine Performance Diagram Fig. 6 Vehicle Performance Diagram

The figures show that a very significant difference lies in the torque characteristics. This curve was

considered possible due to cleaner burning nature of CNG such as no smoke even when the excess airratio is small in comparison to diesel.

An ELF with its payload at 2 tons was used as the base vehicle, and the engine was selected based on

4H* - TC at 4.5 liters. Table 3 shows the main specifications of the vehicle, ELF, and Table 4, those of

the engine.

Table 3 Comparison of Main CNG Vehicle

Specifications Between Production and

Prototype

Table 4 Main Engine Specifications

4.2 Target, approach, and results for each systemThe overall engine system configuration is shown in Fig. 7. The sub-systems unique to this prototype

are described below

1. Fuel systemFig. 8 shows the outline of the ISUZU and Westport fuel system configuration. The maximum

pressure for in-cylinder direct injection of fuel was set at 25 MPa. The reasoning behind this is shown

in Fig. 9: the maximum internal pressure of the cylinders of the engine during operation was 15 MPa;fuel can be injected during combustion; and, the injection pressure should be higher than the cylinder

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CNG TANK

SPOOL VALVE

HYDRAULICPRESSURE RELIEVE

VALVE

H62 COMPRESSOR

ACCUMULATOR

PRESSUREREGULATOR

GAS FILTER

HYDRAULICTANK

HYDRAULICAFTERCOOLER

HYDRAULICPUMP

HYDRAULICFILTER

0

5

10

15

20

25

-90 0 90

Crank angle (deg)

Pressure(MPa)

=12boost1.5bar

=18boost1.5bar

Pressure differenceFor nozzle sealMPa

Pressure differenceFor injection control>MPa

internal maximum pressure by 5 MPa at the minimum. The latter is to ensure the stable sealing

capability of gas seal valves under the internal pressure of cylinders. Also considered was the fact thatthis was a technology under development and the possibility of testing the engine up to 18 MPa withEGR, etc.

Spoolvalve

Variable

nozzleturbocharger

Urea tanl moduleUrea tanl moduleUrea tanl moduleUrea tanl module

EGR valve

EGR cooler

Air

Air

Cleaner

Intercooler

Inlet manifold

Common rail Regulator

Water Temp.sensor

Fuel pressuresensor

Crank

anglesensor

Camangle

sensor

Fuel temp.sensor

fuelfilter

Accumulator

Heat exchanger

One-wayvalve

Oil

pressuretank

Main tap

One-wayvalve

Compressor

Silensor

Exhaust gas

Boostsensor

Air temp.

sensor

Air temp sensor

Temp.

sensorNOUrea catlyst

NOx

sensor

Glowplug

Electricalcontrol

Throttle valve

CNGfilling

Oil

pressurepomp

Relief valve

Fuelfilter

Pressure

sensor

Temp

sensor

Manual

Cut-off valve

Pressuresensor

Relief valve

Eletricalcontrol

cut-offvalve

Relief valve

HC catalyst

Urea tankUrea

pump

CH3 catalystNOx

sensor

Temp.

sensor

FUEL CONDITIONING UNITFUEL CONDITIONING UNITFUEL CONDITIONING UNITFUEL CONDITIONING UNIT

HYDRAULICHYDRAULICHYDRAULICHYDRAULIC

CONTROL PANELCONTROL PANELCONTROL PANELCONTROL PANEL

COMPRESSOR MODULECOMPRESSOR MODULECOMPRESSOR MODULECOMPRESSOR MODULE

CNG tank

Heat exchanger

Eletrical

control

cut-offvalveManual

Cut-off valve

Eletrical

control

cut-offvalve

Fig. 7 Entire System of CNG Engine

Fig. 8 Fuel Delivery System Fig. 9 Maximum Combustion Pressure In

Comparison to Fuel Injection Pressure

Fig. 10 shows a prototype injector assembly. The injection characteristics are shown in Fig. 11, whichshows injection can be made over the entire range from idle, torque, and power as targeted

(controllable). The cross section of this injection nozzle is shown in Fig. 12, with a magnetostrictiveelement employed for direct needle lift control. The coil surrounding the element produces a

magnetic field by inputting electrical current from outside. The element has a different degree of

displacement depending on the strength of the magnetic field; it is possible to control the needle liftwith the electrical power input. Fig. 11shows the relationship between the needle lift, duration and

injected quantity.

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0

10

20

30

40

50

60

70

80

90

100

110

120

0 500 1000 1500 2000 2500 3000

Duration sec

Massflow

mg/injection)

100% Lift

75% Lift

50% Lift25% Lift

Flow @ idle mg/Injection@25MPa 13AFlow @ max torque [mg/Injection]@25MPa 13AFlow @ max power [mg/Injection]@25MPa 13A

30CAD at 2200rpm13CAD at 900rpm

0.75CAD at 500rpm

0

10

20

30

40

50

60

70

80

90

100

110

120

0 500 1000 1500 2000 2500 3000Duration sec

Massflow

mg/injection)

100% Lift

75% Lift

50% Lift

25% Lift

Fig. 10 Injector Assembly

Fig. 11Characteristic of Fuel Injection on

Injection Nozzle (25 MPa)

Fig. 12 Sectional Structure of Injector Fig. 13 Characteristic of Fuel Injection on

Injection Nozzle (10 MPa)

This is one of significant features of the common-rail injection system employed in this engine,because one of the primary aims of this project is to control combustion. In other words, it was our

strong desire to retain the feature of diesel engines: while the pre-mixing combustion is relatively

difficult to control, the diesel combustion is controllable from the ignition timing to combustionconditions (diffusion combustion).

Diesel fuel is liquid, and the internal pressure of the common rail (injection pressure into the cylinders)

is fully changeable as intended through a few repeated injections. Gaseous fuels are, on the otherhand, compressive and difficult to control to produce the optimum common rail pressure even with

rapid changes in the operating range on the engine side.

This new injector, however, controls the needle lift and produces the same effect as if the pressure ischanged in the common rail. Fig. 13 shows the injection characteristics at 10 MPa. As a matter of

fact, the comparison between Fig. 11and Fig. 13 indicates that a 50% lift at 25 MPa produces avirtually equal injection volume as a 100% lift at 10 MPa. It represents exactly the same effect offreely changing the common rail pressure cycle by cycle. It has been shown that this feature is

extremely beneficial in noise reduction as well as in stable ignition and combustion in the idling andlight load range (relatively low fuel flow).

Fig. 14 is a schematic of the hydraulic system for the compressor. Fig. 15 shows a cross section of a

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Atmosphere pressure

M

TURBO

SUPPLY

High pressure

Low pressure circuit

TO COMPRESSOR

HYDRAULICMOTOR

PRV

COOLER

FILTER CylinderCylinderCylinderCylinder

FloatingFloatingFloatingFloatingpistonpistonpistonpiston

MagnetMagnetMagnetMagnet SensorSensorSensorSensor

Oil roomGasroom

WorkingWorkingWorkingWorking

oiloiloiloil

Fuel tankFuel tankFuel tankFuel tank

Common railCommon railCommon railCommon rail

CylinderCylinderCylinderCylinder

FloatingFloatingFloatingFloatingpistonpistonpistonpiston

MagnetMagnetMagnetMagnet SensorSensorSensorSensor

Oil roomGasroom

WorkingWorkingWorkingWorking

oiloiloiloil

Fuel tankFuel tankFuel tankFuel tank

Common railCommon railCommon railCommon rail

IntakeIntakeIntakeIntake

ExhaustExhaustExhaustExhaust

AirCleaner

Variable nozzle turboElectrical throttle valve

IntakeIntakeIntakeIntake

ExhaustExhaustExhaustExhaust

intercooler

Air cleaner

Catalyst

EGR cooler

EGR valve

fuel compressor which has a free-floating piston that divides the cylinder into a compression chamber,

which is filled with fuel and a drive chamber which is filled with hydraulic fluid. Meanwhile a use oftwo compressors as a pair replacing the supply pump on the diesel engine with an oil pump forcompressor has produced a highly efficient compressor system

Fig. 14 Compressor System Fig. 15 Cross Section of Compressor

2. Ignition system.

ISUZU and Westport developed the continuous heat, hot surface ignition system that is employed inthis engine. The system utilizes specially shielded glow plug to generate the hot surface. The shieldcompletely encloses the glow plug and is employed for stable ignition, reliability and durability. Fig.

16 shows the relative orientation of injection nozzle with a hot surface system mounted in the cylinderhead at an inclined angle. The successful demonstration of this ignition system in the Elf truck and

the performance and efficiency results achieved in test cells have shown that this concept has greatpotential. However, the selected plug takes somewhat longer to warm up the glow plug. More works

is needed not only in the temperature increase characteristics but also in reliability and durability.

Fig. 16 Installation of Glow Plug to Cylinder

Head

Fig. 17 Intake and Exhaust System

3. Air intake and exhaust systemFig. 17 shows an outline of the air intake/exhaust system. For the purpose of conducting different

studies, an electric air intake controller was installed. The EGR system has its connecting passagewaysand the cooler doubled in size in order to allow up to twice as much volumetric flow as that of base

diesel engine. Note that the EGR mixing point with intake is actually the inlet of the turbo becausethere is no black smoke generated.

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Local area noise (Engine uppper 50cm)

50

55

60

65

70

75

80

85

90

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

Frequency (Hz)

SPL(dBA)

CNG-DI 50% 1000 89.4

DIESEL 50% 1000 87.7

Autospectrum(Top) - Mark 1

Working : CNG_50_1000 : Input : Time Capture Analyzer

0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]

[dB(A)/20.0u Pa][s] (Nominal Values)

10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0



0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]


10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0

CNG-DI 50%Load 1000rpmAutospectrum(Top) - Mark 1Working : CNG_50_1000 : Input : Time Capture Analyzer

0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]


10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0



0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]


10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0

CNG-DI 50%Load 1000rpmAutospectrum(Top) - Mark 1Working : CNG_50_1000 : Input : Time Capture Analyzer

0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]


10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0



0 1k 2k 3k 4k 5k 6k

40m

80m

120m

160m

200m

240m

280m

[Hz]


10.0

14.017.220.4

24.4

28.4

32.435.638.842.0

46.049.252.455.6

59.662.866.069.2

73.276.479.682.8

86.890.0

CNG-DI 50%Load 1000rpm

Fig. 18 illustrates the variable nozzle-turbo charger system, and a photo of the system is Fig. 19. The

system controls the boost and has a feedback for VNT position.

Fig. 18 Variable Nozzle Turbo Charger (VNT)

System

Fig. 19 Appearance of Variable Nozzle Turbo

Charger (VNT)

4. Other modifications

Principal areas of the engine remain the same as the base diesel engine; for instance, the combustion

chamber of the piston has the same shape, with a compression ratio of= 18.0. Cooling and

lubrication systems are also the same as in the base diesel engine.

4.3 Noise and vibration

Latest diesel engines are common rail types and, combined with pilot injection and other technologicaladvances, are far superior in vibration and noise to conventional diesel engines. Fig. 20 shows a noise

comparison between the latest diesel engine model under development at Isuzu and the engine studiedin this project. It was noted that our engine had a jarring noise (2000 to 4000 Hz), occurring every

two revolutions.

Fig. 20 Comparison of Engine Noise (The

Newest Diesel Engine vs. CNG-DI)

Fig. 21 Search for Noise Source at the Frequency

Band between 2k and 4kHz

Fig. 21 shows one example of such noise. The subsequent study found that the cylinder heads were

acting as speakers for the injectors seating noise. Today it has been improved to a degree such thatthis noise is virtually inaudible. The combustion noise was demonstrated to be sufficiently low in

comparison with that of diesel engines. Fig. 22 shows one example. In fact, the noise heard at thestart of the vehicle is quite mellow, without any resemblance to the noise of the diesel cycle. It is

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10

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

1.0

1.01.0

4.0

2.0

1.3

1.5

1.0

1.3

1.5

2.0

4.0

(%)

0

20

40

60

80

100

120

140

160

Pmax(MPa),

Comb.

noise(dBA)

Pmax Comb. noise

Full load 1000rpm

; CNG - DI

; Diesel

Pmax Comb. noise

Full load 1500rpm

Pmax Comb. noise

Full load 2200rpm

Converted by *

**** CNL = CPL + SA + ACNL = CPL + SA + ACNL = CPL + SA + ACNL = CPL + SA + A---- weightweightweightweightCNL [dB(A)]: Combustion Noise Level

CPL [dB] : Cylinder Pressure Level

SA [dB] : Structure Attenuation

A weight : (Audibility Compensation - A)

Grasp optimum combustion

condition used CFD*

0

2000

4000

6000

8000

10000

12000

14000

-90 -70 -50 -30 -10 10 30 50

Grasp air flow

compression stroke

Grasp fuel spray in and

around glow plug

Grasp optimum ignition

condition used CFD*

Compression stroke CombustionExpansion strokeTDC

Cylinder pressure

* CFD ; Computational Fluid Dynamics

Grasp optimum combustion

condition used CFD*

0

2000

4000

6000

8000

10000

12000

14000

-90 -70 -50 -30 -10 10 30 50

Grasp air flow

compression stroke

Grasp fuel spray in and

around glow plug

Grasp optimum ignition

condition used CFD*

Compression stroke CombustionExpansion strokeTDC

Cylinder pressure

* CFD ; Computational Fluid Dynamics

likely caused by the fact that CNG has one less physical transition as in gas ignition combustion

than diesel as in liquid gas ignition combustion.

Fig. 22 Differences of Combustion Noise Fig. 23 Coefficient of Variation of Combustion

(COV; Pmax) before Fine Tuning

Fig. 23, on the other hand, shows the fluctuation of maximum combustion pressure, the factor affectingvibration, by coefficient of variation of Pmax (maximum peak cylinder pressure). As seen, there is no

problem since fluctuation is within 5% over the entire range, thereby satisfying the target.

4.4 Combustion related simulation by CAE

1. Simulation approach

Fig. 24 describes the development of simulation in each phase, with the aim of faithfully simulating theairflow compression gas injection mixing/ignition combustion expansion in the cylinder

so that computation can reach the level of sufficient agreement with actual test results. STAR-CD was

employed for flow analysis from compression to spraying/flow, WC-ERC combustion model,developed by the Wisconsin University Engine Research Center, was used in combination with

STAR-CD from ignition to combustion.

Fig. 24 Simulation of Combustion Process

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Factor First Second Third

AIn-cylinder temp.() 400 550 700

BCylinder pressure (bar) 50 70 90

CInjection pressure (bar) 100 120 140

DInjection hole (mm) 0.1 0.15 0.2

EInjection duration (ms) 0.3 0.6 0.9

FInjection angle () 7.6 13.6 19.6

GInjection angle () 7.3 9.7 12.1

HGlow plug temp. () 1050 1200 1350

IShield & Glow gap (mm) 0.100 0.225 0.350

JGlow plug & Shield relative position (mm 0 2 4

Liftporsion

Hole Inlet

Fuel passage

Hole outlet

Sack andhole portion

2. CAE results and engine test

Since not much was known on the relationship between fuel jets and ignition, computation studies wereconducted by changing different factors contributing to combustion at three levels in a 27-runstructured design in order to find out how mixing affected combustion. They were followed by a

study in 9-run design to obtain the contributing ratio to combustion and optimum level of each factor.One such example is presented in Fig. 25. The surface temperature of glow plug and injectionpressure, among other things, were found to have large impacts on combustion.

Fig. 25 A Sample of CFD Analysis

The most difficult part was the transition from ignition to combustion. In the ERC model, CNGcombustion was not calibrated; we selected to determine them out by matching them to test results.

Initially we focused on test results from shock tube experiments. Pressures were successfully simulatedwith great accuracy, but we were troubled by little success in the ignition to combustion process. It was

finally understood that there is a fundamental difference in the subject and actual ignitions. In otherwords, it was a difference between the combustion process of high temperature oxidation at 2000 or

higher of a shock tube and that of low-temperature oxidation premixing/diffusion combustion in thecylinder.

Subsequently this problem was resolved, but this gap between the data and the simulation was awake-up call: the true simulation of combustion is impossible unless the injection characteristics in

actual combustion are accurately reproduced. It was therefore decided that we do some more work onthe accurate simulation of actual injection. Fig. 26 shows such an example. In order to ensure if this

simulation actually matched the real injection, methane was injected into a constant pressure vessel andobserved (Fig. 27), and the result was closely compared with the computation results.

Fig. 26 Duplication of Fuel Injection Fig. 27Injection Visualization

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Reduction by

EGR

g/kWg/kWg/kWg/kWhhhh

Final TargetFinal TargetFinal TargetFinal Target


Reduction ratio by catalyst

(Target)

Before catalystBefore catalystBefore catalystBefore catalyst

TargetTargetTargetTarget

(Engine out)(Engine out)(Engine out)(Engine out)


Reduction by

EGR





(Target)

Reduction by

EGR






(Target)

Before catalystBefore catalystBefore catalystBefore catalyst

TargetTargetTargetTarget

(Engine out)(Engine out)(Engine out)(Engine out)


0

5

10

15

-20 -10 0 10 20 30 40 50 60

C.A.(deg)

P

[MPa]

exp.#1_cyli. 100Nm SOI: -15 ATDCexp.#2_cyli. dittoexp.#3_cyli. dittoCFD -A01 ( 100Nm, SOI: -15 ATDC )exp.#1_cyli. 300Nm SOI: -15 ATDCexp.#2_cyli. dittoexp.#3_cyli. dittoCFD -B01 ( 300Nm, SOI: -15 ATDC )exp.#1_cyli. 475Nm SOI: -15 ATDCexp.#2_cyli. dittoexp.#3_cyli. dittoCFD -C01 ( 475Nm, SOI: -15 ATDC )A01Aft (100_-15)B01Aft (300_-15)C01Aft (475_-15)

Fig. 28 shows the results from the experiment and the computation plotted together in one chart.

Although there are still some differences in the absolute values, a very close simulation to the actualengine data became possible from the start of combustion, timing and profile of pressure changes(thermal generation). Thus it is now indicated that computer simulations are now possible using

different values of different parameters, a very valuable tool indeed from now on. This is one of theinnovations we have led the world. Fig. 29 shows one example of such analysis of injection tocombustion in the cylinder.

Fig. 28 Comparison of Simulation and Actual

Fuel Injection P-

Fig. 29 A Sample of Pictorial Playback

According To Combustion Process

5. Development of aftertreatment

5.1 Allocation of emission between engine and aftertreatmentFig. 30 shows the allocation of emission between the engine (with EGR) and aftertreatment in order to

achieve the target emission levels. In other words, the engine was to reduce NOx to 10 12 g/kWhby itself without any processing in the G 13 Mode, which was then to be further reduced by EGR to 4

4.5 g/kWh.

Fig. 30 Contribution of Emission Reduction

Thus the target level would become reachable by aftertreatment, accomplishing a reduction of 80 to85% in NOx from this level. It was indeed the target for NOx reduction of aftertreatment. The

target for NMHC was a 90% or more reduction through aftertreatment. NMHC was presumed toaccount for 20% of THC, and the THC was tuned to produce 9 g/kWh or less before catalyst.

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13

0

10

20

30

40

50

60

70

80

90

100

100 150 200 250 300 350 400 450 500 550 600

Catalyst inlet temp.

NO

conversion

%

Urea-SCR low temp active typeLNT High temp active type

Turbo chargerTurbo chargerTurbo chargerTurbo charger

Urea injectorUrea injectorUrea injectorUrea injector

ENGINEENGINEENGINEENGINE

1 Oxidation catalyst : For CH4 conversion (Mianly low load)

2 Oxidation catalyst : For CH4 conversion (Mianly high load)

3 Oxidation catalyst : For chang NONO2 & CH4 conversion

4 SCR catalyst : For NOx conversion

5 Oxidation catalyst : For prevention of ammonia slip

Mainly function of catalystMainly function of catalystMainly function of catalystMainly function of catalyst

TurboTurboTurboTurbo

UreaUreaUreaUrea

ENGINENGINENGINENGINENGINENGINENGINENGIN

1 Oxidation catalyst : For CH4 conversion (Mianly low load)

2 Oxidation catalyst : For CH4 conversion (Mianly high load)

3 Oxidation catalyst : For chang NONO2 & CH4 conversion

4 SCR catalyst : For NOx conversion

5 Oxidation catalyst : For prevention of ammonia slip

Mainly function of catalystMainly function of catalystMainly function of catalystMainly function of catalyst

0

10

20

30

40

50

60

70

80

90

100

50 100 150 200 250 300 350 400 450 500 550 600

Catalyst inlet Temp

CH4conversion

(%)

Pt/Pd system A

NO oxidation catalyst Pt system

Pt/Pd system B

Pt/Pd system C

ItemItemItemItem

No conversionNo conversionNo conversionNo conversionprospectprospectprospectprospect 20 3020 3020 3020 30 60 7060 7060 7060 70 80 9080 9080 9080 90

Fuel economyFuel economyFuel economyFuel economyprospectprospectprospectprospect

2-5%2-5%2-5%2-5% 12%12%12%12% 1.6-2.1%1.6-2.1%1.6-2.1%1.6-2.1%

(Include urea(Include urea(Include urea(Include ureacost)cost)cost)cost)

DurabilityDurabilityDurabilityDurability

Light-off temp.Light-off temp.Light-off temp.Light-off temp. 200-300Pt200-300Pt200-300Pt200-300Pt

seriesseriesseriesseries350-500Base350-500Base350-500Base350-500Basemetal seriesmetal seriesmetal seriesmetal series

300 4 50300 450300 450300 4 50 200 600200 600200 600200 600

Catalyst sizeCatalyst sizeCatalyst sizeCatalyst size times as times as times as times asdisplacementdisplacementdisplacementdisplacement

times as times as times as times asdisplacementdisplacementdisplacementdisplacement

times as times as times as times asdisplacementdisplacementdisplacementdisplacement

WeightWeightWeightWeight Increase (UreaIncrease (UreaIncrease (UreaIncrease (Ureatank & systems)tank & systems)tank & systems)tank & systems)

PackagingPackagingPackagingPackaging catalyst onlycatalyst onlycatalyst onlycatalyst only catalyst onlycatalyst onlycatalyst onlycatalyst only Urea tank &Urea tank &Urea tank &Urea tank &InjectionInjectionInjectionInjectionsystemsystemsystemsystem

InfrastructureInfrastructureInfrastructureInfrastructure UreaUreaUreaUrea

Engine controlEngine controlEngine controlEngine control Post injectionPost injectionPost injectionPost injection Rich-leanRich-leanRich-leanRich-leancombustioncombustioncombustioncombustioncontrolcontrolcontrolcontrol

No needNo needNo needNo need

combustioncombustioncombustioncombustioncontrolcontrolcontrolcontrol

Total evaluateTotal evaluateTotal evaluateTotal evaluate Low conversionLow conversionLow conversionLow conversion Low conversionLow conversionLow conversionLow conversionHard to controlHard to controlHard to controlHard to control

Rich/LeanRich/LeanRich/LeanRich/Lean

High potentialHigh potentialHigh potentialHigh potentialperformanceperformanceperformanceperformance( Need Urea( Need Urea( Need Urea( Need Urea

systemsystemsystemsystemInstallation andInstallation andInstallation andInstallation and

down sizingdown sizingdown sizingdown sizingcatalystcatalystcatalystcatalyst

HC-SCR catalystHC-SCR catalystHC-SCR catalystHC-SCR catalystLean NO trapLean NO trapLean NO trapLean NO trap

catalystcatalystcatalystcatalystUrea-SCR catalystUrea-SCR catalystUrea-SCR catalystUrea-SCR catalyst

5.2 System selection and basic study (gas model)

Fig. 31 shows an overview of the systems involved in the aftertreatment selection, in which candidateswere first listed up for study. For the reduction of HC, a study using a model gas was conducted toselect a coating material with higher oxidation property because of the high stability of CH4. Fig. 32

shows the sample a coating material with pt/pd series was selected.Table 5 provides the overview of characteristics of the candidate agents for the reduction of NOx.HC-SCR catalyst was eliminated from the selection pool early in the process due to its conversion ratio.Studied were NOx absorber (LNT) and urea-SCR catalysts. In the case of LNT, it was found that a) it

would unlikely produce the target conversion rate; b) the cost would be higher than other options forthe same level of NOx reduction (approximately twice or more of SCR); and, c) it would not reduce

CH4 and therefore require the engine to control injection and combustion for the reduction process to

occur due to the need for unsaturated gas of CO or C3H8 and higher hydrocarbons. These led to thefinal selection of the urea-SCR catalyst. Fig. 33 shows one example of the basic study of LNT

catalyst.

Fig. 31 Possible After Treatment system

(Proposal)

Fig. 32 Selection Test of Catalyst for CH4

Table 5 Comparison of Characteristic of NOx

Catalysts

Fig. 33 Basic Test of NOx Absorbed Catalyst

Fig. 34 describes one example of coating material tests with a model gas for SV ratio (catalyst size)which was conducted to determine the urea-SCR catalyst. When urea-SCR catalyst was chosen, thestudy of coating material properties for ammonia catalyst was initiated using a model gas in

consideration of urea slip.

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14

0

10

20

30

40

50

60

70

80

90

100

100 150 200 250 300 350 400 450 500 550 600


NO

conversion

%

Low temp. active type

High temp. active type

SV30000O2 10H2O 6NO 200ppmNH3 200ppmTemp rise speed 5/min

Catalyst size Temp.(Prospect)

Pressure loss(Prospect)

Remarks

35.5mm70mm 750 18 (kPa)200cell/cell thickness 60

m Metal honeycomb

5.66"4.84" 700 6.6 (kPa)400cell/cell thickness6mill Ceramic honeycomb

5.66"4.84" 700 5.4 (kPa)300cell/cell thickness8mill Ceramic honeycomb

7.5"7" 650 4.9 (kPa)400cell/cell thickness6mill Ceramic honeycomb

9"12" 600 5.3 (kPa)400cell/cell thickness6mill Ceramic honeycomb

9"4" 600 2.3 (kPa)400cell/cell thickness6mill Ceramic honeycomb

Under floorNO Oxidation catalyst

Under floorUrea-SCR catalyst

Under floorCH3-slip catalyst

Position

Pre-TurboOxidation catalyst

Post-TurboOxidation catalyst

Post-TurboOxidation catalyst

HCOxidationcatalyst

UreaPump

NOOxidationCatalyst

SCRCatalyst

CNG Engine

Ureacontrol PC

EngineECU

Tank

Temp.sensor

Ureainjector

UreaInjectionECU

HCOxidationcatalyst

HCOxidationcatalyst

UreaPump

NOOxidationCatalyst

NOOxidationCatalyst

SCRCatalyst

CNG EngineCNG Engine

Ureacontrol PC

EngineECU

Tank

Temp.sensor

Ureainjector

UreaInjectionECU

Fig. 34 Basic Test of Urea SCR Catalyst

Table 6 Estimation of Exhaust Pressure Drop forEach Catalyst

Fig. 35 Pre-Turbo HC Catalyst

In addition, the target for the total back pressure was set at 20kPa or less from the beginning since

incorporating these catalysts after the engine would increase the back pressure, thus affectingefficiency. Table 6 shows the calculated backpressure of each catalyst. As seen, the

backpressure is high at 18 to 20kPa with these catalysts alone; the use of catalysts at the turbointake for HC reduction was therefore abandoned. Fig. 35 shows a prototype HC catalyst system

for the entrance of the turbo.

5.3 SCR system1. System and rig test results

Fig. 36 shows the system drawing of the SCR catalyst. Isuzu has been engaged in the R&D ofurea-SCR catalysts for heavy-duty engines but only in the air-assisted uniform injection approach ofurea water solution over the exhaust pipes. Since this study was for light-duty vehicles, which have

no high-pressure air sources, there was no choice but to employ the direct injection of urea water.

Fig. 36 Urea SCR Catalyst System

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15

0

5

10

15

20

25

30

35

40

0 0.1 0.2 0.3 0.4 0.5

Duty ratio A/(A+B)

Massflow(g/m)

Max. Target

Min. Target A B

Duty ratio

+

Exhaust gas flow

Exh. Gas temp.

Low load & rpm

Urea injector position

Impactor

Diameter

SCR

Catalyst

Exhaust gas flow

Exh. Gas temp.

Low load & rpm

Urea injector position

Impactor

Diameter

SCR

Catalyst

In our system, a large amount of urea water is constantly circulated at a certain pressure, and injections

are made through the control of the duty ratio by an electromagnetic valve in its circuit. Fig. 37 is aphoto of the injection device, while Fig. 38, an example of injection characteristics.

Fig. 37 Appearance of Urea SCR Injector Fig. 38 Characteristic of Urea SCR Injector

2. Novel concepts for better efficiency in uniform atomization and vaporization.

As shown in the picture, the urea water injector has one injection hole with a reflector panel set at a45-degree angle. The mounting position and other factors for the injector were studied using CAE in

order to ensure that the resultant spray would enter the catalyst uniformly and fully vaporized. Fig. 39shows one such example. For the reduction of actual emissions, different exhaust pipe configurationswere studied to produce better uniformity of atomization and vaporization. It was finally concluded the

cone-shaped piping produced favorable results. The photos in Fig. 40 are the tested exhaust pipes.

Fig. 39 Urea Flow Simulation with Injection, diffusion and Vaporization by CAE

Fig. 40 Prototype Diffuser Cone and Exhaust Pipe System

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16

42

33

43

71

83

91

79

56

75

46

64

84

7983 84 84 83

89

98 98

81

99100100

0

10

20

30

40

50

60

70

80

90

100

M2 M3 M5 M6 M7 M8 M9 M10 M11 M12 IDLE TOTALMODE NUMBER in G13Mode

NOxconversion(%)

W/O Oxidation Catalyst

W/ Oxidation Catalyst

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

1100

700

400

250

120

160

120

160

250

400

700

1100

(ppm)

0

10

20

30

40

50

60

70

80

90

100

50 100 150 200 250 300 350 400 450 500 550 600


NOconversion

(%)

Pt/Pd sytem A

NO oxidation catalystPt systemPt/Pd system B

Pt/Pd system C

Measurementpoint

NOx THC CO CO2COVlevel

Initial test resultInitial test resultInitial test resultInitial test result Engine outEngine outEngine outEngine out 8.78.78.78.7 5.825.825.825.82 6.476.476.476.47 626626626626TargetTargetTargetTargetachievemachievemachievemachievementententent

TargetWithout EGR,Catalyst)

Engine out 12 6.5 15 600

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17

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

30

30

50

100

200

30020

30

50

100

200

300

(ppm)

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

300

2000

2000

1000

900

900

700

700

500

500

500

300

500

700

900

1000

2000

(ppm)

02468

10

0

100

200

0

7500

15000

0

100

200

0

150

300

-5 0 5 10 15 20

CO(g/h)

CO(g/h)

CO(g/h)

CO(g/h)

2(g/h)

2(g/h)

2(g/h)

2(g/h)

THC(g/h)

THC(g/h)

THC(g/h)

THC(g/h)

NOx(g/h)

NOx(g/h)

NOx(g/h)

NOx(g/h)

COV(%)

COV(%)

COV(%)

COV(%)

EGR ratio EGR ratio EGR ratio EGR ratio

0

2

4

6

0

150

300

0

8500

17000

0

25

50

0

250

500

0 2 4 6 8 10 12 14

CO(g/h)

CO(g/h)

CO(g/h)

CO(g/h)

2(g/h)

2(g/h)

2(g/h)

2(g/h)

THC(g/h)

THC(g/h)

THC(g/h)

THC(g/h)

NOx(g/h)

NOx(g/h)

NOx(g/h)

NOx(g/h)

COV(%)

COV(%)

COV(%)

COV(%)

Injection timingBTDC)Injection timingBTDC)Injection timingBTDC)Injection timingBTDC)

0

200

400

600

800

1000

1200

1400

1600

1800

Decrease by EGR

Decrease by timing retard

NOx Con. After the ta il pipe

2 3 5 6 7 8 9 10 11 12

Fig. 44 Characteristic of HC before Fine Tuning Fig. 45 Characteristic of CO before Fine Tuning

Fig. 46 Characteristic of EGR before Fine

Tuning

Fig. 47 Investigation of Contribution of Injection

Timing and EGR to Emission Reduction

One example of the study on the contributing factor for different emission properties by changing,among other things, injection timing and EGR ratio is presented in Fig. 47. Fig. 48 shows oneexample of the studies done for reduction rate and ammonia slip by changing the urea-SCR conditions.

Fig. 49 shows the temperature of engine exhaust gas at different points in the after flow in each of the

G 13 Mode. This figure illustrates the challenges of reaching targeted the thermal efficiency (nonegative influence on CO2) while increasing the exhaust temperature (for utilizing catalyst bymaintaining the temperature at the catalyst activation temperature or higher.)

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Ureapump

Diffusion coneOxidationcatalyst

SCRcatalyst

CNG-DI Engine

UreainjectionECU

Ureacontrol PC

Engine ECU

Tank

Ureapump

Diffusion coneOxidationcatalyst

SCRcatalyst

CNG-DI Engine

Diffusion coneDiffusion coneOxidationcatalyst

Oxidationcatalyst

SCRcatalystSCR

catalyst

CNG-DI EngineCNG-DI Engine

UreainjectionECU

Ureacontrol PC

Engine ECU

Tank

NOx NMHC CO CO2 COV

(g/kWh) (g/kWh) (g/kWh) (g/kWh) (%)

Final resultFinal resultFinal resultFinal result 0.510.510.510.51 0.100.100.100.10

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19

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

10

102020

20

40

40

60

60

80

100

10

20

40

60

80

100

(ppm)

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

90

60 40

40

10

10

20

20

10

20

40

60

90

(ppm)

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

7500

8600

12000

13000

14000

15000

7500

8600

12000

13000

14000

15000

(kPa)

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

1.5

1.5

2.02.0

.5

2.5

3.0

4.04.0

(lamda)

1.5

2

2.5

3

4

Load(Nm)

0

50

100

150

200

250

300

350

400

450

500

Engine Speed (rp m)

800 1000 1200 1400 1600 1800 2000 2200

ALL AREA 0 ppm

Overall length

Overall width

Overall height

Wheel base

Maximum payload

Occupant

GVW

As seen from this table, all targets were achieved. The engine characteristics are shown in 51 to 55

(emission: NOx, HC, CO, Pmax, , etc.)

Fig. 51 Diagram of NOX with Final Engine

Specifications

Fig. 52 Diagram of HC with Final Engine

Specifications

Fig. 53 Diagram of CO with Final Engine

Specifications

Fig. 54 Diagram of Pmax with Final Engine

Specifications

Fig. 55 Diagram of Excess Air Ratio () with

Final Engine Specifications

Table 9 Summary of Main Vehicle Specifications

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Oxidationcatalyst

Urea catalyst

Silencer Tank

Tank

Fuel compressor

Heatexchanger

Acumulator

Regulator

Urea supplysystem

Aircleaner

7. Vehicle development

7.1 Vehicle specificationThe target performance for the vehicle was, as mentioned earlier, based on the 2-ton ELF-CNGV, avery popular model currently available on the market with fuel economy and driveability that replicate

those of diesel vehicles rather than those of gasoline vehicles. Fig. 56 shows the appearance of thedeveloped vehicle, while Table 9 presents its major specifications.

7.2 Vehicle layout and development

Fig. 57 shows the assembly of the frame and components. Fig. 58 shows simplified schematics ofdifferent systems in the vehicle. Fig. 59 is an electrical plan for coordination and control of these

systems. There is the main engine ECU, CNG-related ECU, and emission-related ECU (for

urea-SCR), all integrated through CAN BUS for control as a vehicle.

Fig. 56 Appearance of Completed Vehicle

Fig. 57 Drawing of Layout Plan for Vehicle Fig. 58 Schematics of Different System Layout

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AP sensor

Idle switch

Switch

A/C switch

Glow relay

Check engine ramp

Injector driver

Glowplugdriver

Main

Engine

Control

Module

Urea

Injector

Control

module

Sub

Engine

Control

Module

Vehicle

Interface

Module

Crank angle sensor

Cam angle sensor

Intake throttleposition sensor

VNT positionsensorVNT control

Intake throttle drive

Injector drive

Glowplugdrive

Inletair temp. sensor

MAP sensor

Common rail pressuresensor

Fuel temp. sensor

Common rail

Injector

EGR cooler

Ignition switch

Starter switch

Battery

EXH. Brake

Solenoid valve

Echo relay

EXH.Brake

EXH. Brake ramp

Glowplug ramp

EXH. Brake ramp switch

Stopramprelay

Clutch switch

Neutral switch

Vehicle speedsensor

Parking swwitch

Idle up volume

Tachometer

Vehicle function

EGR valve driveEGR valve position sensor

IAT sensor

Compressormodule

Mainrelay

Battery

Pressure

sensor

AP sensor

Idle switch

Switch

A/C switch

Glow relay

Check engine ramp

Injector driver

Glowplugdriver

Main

Engine

Control

Module

Urea

Injector

Control

module

Sub

Engine

Control

Module

Vehicle

Interface

Module

Crank angle sensor

Cam angle sensor

Intake throttleposition sensor

VNT positionsensorVNT control

Intake throttle drive

Injector drive

Glowplugdrive

Inletair temp. sensor

MAP sensor

Common rail pressuresensor

Fuel temp. sensor

Common rail

Injector

EGR cooler

Ignition switch

Starter switch

Battery

EXH. Brake

Solenoid valve

Echo relay

EXH.Brake

EXH. Brake ramp

Glowplug ramp

EXH. Brake ramp switch

Stopramprelay

Clutch switch

Neutral switch

Vehicle speedsensor

Parking swwitch

Idle up volume

Tachometer

Vehicle function

EGR valve driveEGR valve position sensor

IAT sensor

Compressormodule

Mainrelay

Battery

Pressure

sensor

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000

Drive distance

Vehiclespeed

Km/

Fig. 59 Electric Wiring Diagram of Control

System

Fig. 60 Drive Route for Fuel Consumption Test

8. Results of driving test

8.1 Validation of basic performanceThe validation was performed not only for fuel economy and driveability, but also to achieve a

diesel-equivalent level in low-end torque and exhaust braking as well as a practical level in response,vibration and noise.

8.2 Evaluations at Bibendum 2003The study vehicle was entered in Bibendum 2003; a competition organized by Michelin that was heldfrom September 23 to 25, 2003 in California. The participating vehicles went through strict evaluations

based on ISO. Our vehicle earned the following awards in recognition of our achievements:

A) Fuel economy: Gold medal (absolute values not published); a diesel vehicle ran the same course

for comparison; a distance of 14 miles (approx. 22.5 km) including 45 abrupt starts and stops. Fig.60 shows the driving pattern.

B) Emission: application by document; Gold medal (including the validation of J-G13 Mode and SCRfunctionality)

C) Noise (acceleration): 70.4 dB(A); Silver medal;D) Acceleration: 47.1 miles per hour; Bronze (internal test before the event: 56 57 miles per hour)

due to facing wind and slopes;E) General driveability test, including a rally to the Golden Gate Bridge; (approximately 60 km in the

suburb and approximately 40 km of freeway driving). The vehicle successfully completed the run,receiving the checker flag.

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9. Summary and future challenge

9.1 SummaryWe succeeded in the incorporation of an ISUZU and Westport hot surface ignition CNG-direct injectiondiesel cycle engine in a commercial vehicle and its operation as a complete vehicle for the first time in

the world. As seen in the records at the Bibendum, it was demonstrated that the vehicle has satisfiedall the parameters of a vehicle at a high level, indicating the high potential of this technology forcommercialization in the near future. It is a significant milestone.9.2 Future subjects

a) Pursuit of full reliability and durability: Refinement of ISUZU and Westport fuel, ignition andcontrol systems as required for full commercialization.

b) Further improvements in emission and fuel economy: the test mode for emission will be

changed from G-13 to transition mode. Better fuel economy and cleaner emission must bepursued in line with this change. In addition, commercialization without urea-SCR catalyst

should be explored; and,c) Price reduction, lighter weight, and smaller size must be worked at along with the issues in a)

for the eventual commercialization and sophistication of each system.

I would like to take this opportunity to sincerely thank all those involved for their extraordinarydedication and support, without which we could not possibly have completed and operated the vehicle

in such a short time with such demanding targets. I am certain we can deliver even greaterdevelopments of this technology.

REFERENCES

1. G. Zakis, H C. Watson, 2003, "Alternative Ignition System for CNG in Diesel Applications",

IPC12-D32.2. P. Ouellette, Westport, 2000,"High pressure Direct Injection (HPDI) of Natural Gas in Diesel

Engine", NGV2000.3. T. Komada, Mitsui Eng'ng & Ship, 2004"The Large Gas Injection Engine", ENGINE

TECHNOLOGY 30.4. M. Shioji, Kyoto Unv. 2001,"Study & Research for Ignition and Combustion System of High

Performance Natural gas Engine" JGA-Report.5. M. Oguchi, JARI, 2001,"Research & Evaluation of High Efficiency Natural Gas Vehicle"

JGA-Report.6. M. Okada, Isuzu Motors, 2003,"The Commercial Development of High-Efficiency, Ultra-Low

Emission CNG Vehicles" NEDO-Report.

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