February 2000 • NREL/SR-540-27502

A.K. ChanCaterpillar, Inc.Peoria, Illinois

Ignition Assist Systems forDirect-Injected, Diesel Cycle,Medium-Duty Alternative FuelEngines

Final Report Phase I

National Renewable Energy Laboratory1617 Cole BoulevardGolden, Colorado 80401-3393NREL is a U.S. Department of Energy LaboratoryOperated by Midwest Research Institute !!!! Battelle !!!! Bechtel

Contract No. DE-AC36-99-GO10337

February 2000 • NREL/SR-540-27502

Ignition Assist Systems forDirect-Injected, Diesel Cycle,Medium-Duty Alternative FuelEngines

Final Report Phase I

A.K. ChanCaterpillar, Inc.Peoria, Illinois

NREL Technical Monitor: Keith VertinPrepared under Subcontract No. ZAS-7-16609-01

National Renewable Energy Laboratory1617 Cole BoulevardGolden, Colorado 80401-3393NREL is a U.S. Department of Energy LaboratoryOperated by Midwest Research Institute !!!! Battelle !!!! Bechtel

Contract No. DE-AC36-99-GO10337

This publication was reproduced from the best available copySubmitted by the subcontractor and received no editorial review at NREL

NOTICE

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Acknowledgement

This research was sponsored by Stephen Goguen, Program Manager in the Department ofEnergy’s Office of Heavy Vehicle Technologies. The technical monitor for this project wasKeith Vertin, Senior Engineer at the National Renewable Energy Laboratory.

4Requires extensivedevelopment

2Large

< 1Plasma energy and plumevolume

Early injection of fuel through plasmajet ignitor

Stratified ChargePlasma Ignition

5Fuel supply problems3Large(Injection plume)

2 - 3Fuel additive concentrationand autoignition temperature

Addition of ethane to natural gas toaid autoignition

Fuel Additives

3Pilot fuel consumption issues2Large(Injection plume)

1 - 2Fuel pilot cetane number andquantity

Small quantity of high cetane fluidinjected with natural gas

Micropilot Injection

5Power requirement andemissions issues

2Large(Injection plume)

2 - 3Inlet air temperature andcompression ratio

Inlet air heating and increasedcompression ratio of engine to induceautoignition

Inlet Air Heating

4Cost and component durabilityfar from production

4Small(Laser focal volume)

1 - 2Laser energy and localequivalence ratio

Gases in laser focal volume ionized byintense thermal heating

Laser Plasma

4Cost and component durabilityfar from production

4Small(Laser focal volume)

1 - 2Laser energy and local fuelconcentration

Excitation of fuel molecules in laserfocal volume by laser wavelength

Laser Excitation

5Injector and power supplyrequire development

1Large(Injection plume)

< 1Initial fuel temperatureFuel raised to ignition temperatureprior to or during injection

Fuel Preheating

4Durability requiresdevelopment

5Medium(Layer at pre-chamber wall)

2 - 3Surface Temperature and localequivalence ratio

Heat transfer to mixture from internalhot surface

Heated Pre-chamber

4Durability requiresdevelopment

2Large(Plasma plume volume)

< 1Plasma energy and plumevolume

Plasma generated and propelled intocylinder

Plasma Jet Ignitor

2Durability and electronicsunproven

3Small(Spark plug gap)

1 - 2Local equivalence ratio andspark energy

Multiple sparks with feedback controlSmartFire SparkPlug

2Durability and electronicsunproven

4Small(Spark plug gap)

1 - 2Local equivalence ratio andspark energy

Short duration high power sparkSDHP Plug

2Power supply and controlsrequire development

3Small(Spark plug gap)

1 - 2Local equivalence ratio, sparkduration and spark energy

Long duration high frequency sparkinitiated early in compression stroke

AC Spark Plug

1Durability requiresdevelopment

5Medium(Layer near glow plug surface)

2 - 3Surface temperature and localequivalence ratio

Heat transfer to mixture from externalhot surface

Glow Plug

Action(Note 1)

Production Limiting FeatureEst. COV(Note 2)

Ignition VolumeEst. Ign.Delay(ms)

Determinant of IgnitionDelay

Working PrincipleSource of IgnitionAssist

Note 1: '1' - Continue development. '2' - Initiate development. '3' - Perform concept study. '4' - Monitor outside research. '5' - Will reevaluate if encounter newdevelopment.Note 2: COV = Coefficient of Variation. Scale: 5 - high, 1 - low

Table 1: Direct Injection Natural Gas Engine Ignition Options Survey

Figure 1: Constant volume high pressure chamber

-17-

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

250

300

Bre

akdo

wn

Vol

tage

(kV

)

predicted curve & point - 1.5 mm gap predicted curve & point - 1.0 mm gap predicted curve & point - 0.5 mm gap

Predicted Breakdown Voltage vs Pressure'Uniform-Field' Electrodes

Figure 2: Predicted Breakdown Voltage vs Pressure by Paschen’s law

-19-

Figure 3: 60 Hz AC power supply

Figure 4: Electrode mounting fixture

-21-

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

Bre

akdo

wn

Vol

tage

(kV

)

data point - 1.5 mm gapdata point - 1.0 mm gapdata point - 0.5 mm gapbest fit curve - 1.5 mm gapbest fit curve - 1.0 mm gapbest fit curve - 0.5 mm gap

Breakdown Voltage vs PressureFlat-Flat Electrodes

Figure 5: Breakdown Voltage vs Pressure for Flat-Flat electrodes

-23-

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

Bre

akdo

wn

Vol

tage

(kV

)data point - 1.0 mm gapdata point - 0.5 mm gapbest fit curve - 1.0 mm gapbest fit curve - 0.5 mm gap

Breakdown Voltage vs PressureFlat-Round Electrodes

Figure 6: Breakdown Voltage vs Pressure for Flat-Round electrodes

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

Bre

akdo

wn

Vol

tage

(kV

)

data point - 0.5 mm gapbest fit curve - 0.5 mm gap

Breakdown Voltage vs PressureFlat-Point Electrodes

Figure 7: Breakdown Voltage vs Pressure for Flat-Point electrodes

-26-

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

Bre

akdo

wn

Vol

tage

(kV

)predicted curve & point - Paschen's Lawbest fit curve & predicted point - Flat-Round electrodesbest fit curve & predicted point - Flat-Flat electrodes

Breakdown Voltage vs Pressure0.5 mm Gap

Figure 8: Comparison of breakdown voltages for a 0.5 mm gap

100 200 300 400 500 600 700 800 900 1000 1100

Pressure (psig)

0

50

100

150

200

250

300

Bre

akdo

wn

Vol

tage

(kV

)

predicted curve & point - Paschen's Lawbest fit curve & predicted point - Flat-Round electrodesbest fit curve & predicted point - Flat-Flat electrodesbest fit curve & predicted point - Flat-Point electrodes

Breakdown Voltage vs Pressure1.0 mm Gap

Figure 9: Comparison of breakdown voltages for a 1.0 mm gap

-27-

Figure 10: High frequency AC power supply

-29-

DC Power Supply15 to 20 Volts

20 amps

AdjustableHigh Frequency

Generator

AdjustableSpark Duration

Control

AdjustableSpark

RepetitionRate

Control

Low Voltage Logicto High Voltage

CircuitInterface

"H" BridgeCircuitry

Ignition coilExternal singlespark control

5 VoltRegulator

1 Amp

12 VoltRegulator

1 Amp

108 Volts1 Amp

Continuous17 Ampsurge

Enable

Switch

Disable

Spark Plugin

PressureChamber

Power and Ground

Signal Line

Figure 11: Schematic diagram of the high frequency AC power supply

-30-

Figure 12: EIS (electronic ignition system)

Figure 13: SDHP (short duration high power) ignition system

-35-

0 20 40 60 80 100 120 140 160

Time (micro-seconds)

-50

-40

-30

-20

-10

0

10

Out

put V

olta

ge (k

V)

'Open Circuit' VoltageCoil made by Adrenaline Research Inc.

Figure 14: Voltage Output vs Time

Figure 15: Adrenaline plugs made by Champion

-37-

Figure 16: ‘S martFire’ ignition system

-38-

Figure 17: Spark plug after bench testing with the Adrenaline System (0.46 mm gap)

Figure 18: Spark plug after bench testing with the Adrenaline System (0.51 mm gap)

-40-

Figure 19: Spark plug after bench testing with the Adrenaline System (1.02 mm gap)

Figure 20: Spark plug after bench testing with the Adrenaline System (1.27 mm gap)

-41-

Figure 21: Ceramic disk sandwiched in the portable oil tester

Figure 22: Ceramic disk sandwiched in the portable oil tester submerged the oil bath

-45-

Figure 23: Disks showing original coatings

Figure 24: Disks showing modified coatings

-46-

3.5 4 4.5 5 5.5 6 6.5

Thickness (mm)

20

30

40

50

60

70

80

90

100

110

Bre

akdo

wn

Vol

tage

(kV

)

data point -Diala oildata point - AD-94data point - TiO2best fit curve - Diala oil

Breakdown Voltage vs Thickness

Figure 25: Breakdown Voltage vs Insulator Thickness

-47-

Figure 26: Glow plug shield

-52-

Figure 27: Prototype ceramic insulator body

Figure 28: Prototype spark plug assembly

-54-

Figure 29: Prototype ceramic insulator body for surface-discharge plug

Figure 30: Prototype surface-discharge spark plug assembly

-55-

Figure 31: Central electrode for the air-gap spark plug

Figure 32: Central electrode for the surface-discharge spark plug

-56-

Figure 33: Modified 3126 DING cylinder head

Figure 34: Cutout view showing the glow plug and the spark plug hole

-57-

Figure 35: Sectional view of the glow plug and the air-gap spark plug holes

Figure 36: Sectional view showing the ‘gas retainer/ground electrode’

-58-

Figure 37: Air-gap plug in the cylinder head

Figure 38: Sectional view of the air-gap plug in the cylinder head

-59-

Figure 39: Spark gap between the central electrode and the ground electrode

Figure 40: Sectional view of the glow plug and the surface-discharge spark plug holes

-61-

Figure 41: Surface-discharge plug in the cylinder head

Figure 42: Sectional view of the surface-discharge plug in the cylinder head

-62-

Figure 43: Surface spark gap between the central electrode and the ground electrode

Figure 44: Mounting clamp

-63-

Figure 45: Plug in cylinder head with mounting clamp

Figure 46: Side view of plug in cylinder head with mounting clamp

-64-

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATEFebruary 2000

3. REPORT TYPE AND DATES COVEREDSubcontract Report

4. TITLE AND SUBTITLEIgnition Assist Systems for Direct Injected Diesel Cycle, Medium-Duty Alternative Fuel Engines

6. AUTHOR(S)Anthony K. Chan

5. FUNDING NUMBERSC: ZAS-7-16609-01TA: FU903110

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Caterpillar, Inc.Peoria, Illinois

8. PERFORMING ORGANIZATIONREPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)National Renewable Energy Laboratory1617 Cole Blvd.Golden, CO 80401-3393

10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

NREL/SR-540-27502

11. SUPPLEMENTARY NOTES

NREL Technical Monitor: Keith Vertin

12a. DISTRIBUTION/AVAILABILITY STATEMENTNational Technical Information ServiceU.S. Department of Commerce5285 Port Royal RoadSpringfield, VA 22161

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)This report is a summary of the results of Phase 1 of this contract. The objective was to evaluate the potential of assist technologies fordirect-injected alternative fuel engines vs. glow plug ignition assist. The goal was to demonstrate the feasibility of an ignition system lifeof 10,000 hours and a system cost of less than 50% of the glow plug system, while meeting or exceeding the engine thermal efficiencyobtained with the glow plug system. There were three tasks in Phase 1. Under Task 1, a comprehensive review of feasible ignitionoptions for DING engines was completed. The most promising options are: 1) AC and the “SmartFire” spark, which are both long-duration, low-power (LDLP) spark systems; 2) the short-duration, high-power (SDHP) spark system; 3) the micropilot injection ignition;and 4) the stratified charge plasma ignition. Efforts concentrated on investigating the AC spark, “SmartFire” spark, and short-duration/high-power spark systems. Using our proprietary pricing information, we predicted that the commercial costs for the AC spark,the short-duration/high-power spark and “SmartFire” spark systems will be comparable (if not less) to the glow plug system. Task 2involved designing and performing bench tests to determine the criteria for the ignition system and the prototype spark plug for Task 3.The two most important design criteria are the high voltage output requirement of the ignition system and the minimum electricalinsulation requirement for the spark plug. Under Task 3, all the necessary hardware for the one-cylinder engine test was designed. Thehardware includes modified 3126 cylinder heads, specially designed prototype spark plugs, ignition system electronics, and parts for thesystem installation. Two 3126 cylinder heads and the “SmartFire” ignition system were procured, and testing will begin in Phase 2 of thissubcontract.

15. NUMBER OF PAGES 14. SUBJECT TERMS

Direct injection; alternative fuel engines; ignition assist systems; diesel cycle; medium-dutyengines 16. PRICE CODE

17. SECURITY CLASSIFICATIONOF REPORTunclassified

18. SECURITY CLASSIFICATIONOF THIS PAGEunclassified

19. SECURITY CLASSIFICATIONOF ABSTRACTunclassified

20. LIMITATION OF ABSTRACT

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