Waukesha

Ignition Improvements to Ignition Improvements to Support HighSupport High--efficiency Natural efficiency Natural

Gas CombustionGas Combustion

2005 UW ERC Symposium on Low-Emissions Combustion Technologies

for Internal Combustion Engines

Corey HonlSr. Development Engineer

Waukesha Engine, Dresser, Inc.

Waukesha

AgendaAgenda• Who is Waukesha?• What is ARES?• ARES Phase 1 objectives• Current state of natural gas

lean-burn ignition on stationary engines• Test apparatus and fixed characteristics• Prechamber aspects studied and results• Conclusions

Waukesha

Who is Waukesha Engine?Who is Waukesha Engine?

Waukesha

Our Product LineOur Product Line

Waukesha

What is ARES?What is ARES?• The Advanced Reciprocating Engine Systems

program is a multi-year, co-funded research initiative with the DOE to develop high-efficiency natural gas-fueled engines for DPG.

• Consortium members: DOE, Waukesha Engine, Caterpillar, and Cummins.

• Supporting cast: MIT, CSU,UT-Austin, Ohio State, and Purdue; Argonne, NETL, and ORNL.

• Three phase program to achieve 0.1 gr./HP-hr NOx stack emissions and 50% BTE by 2010.

• www.eere.energy.gov/de/gas_fired/

Waukesha

ARESARES--Waukesha Phase 1Waukesha Phase 1• Performance increase on VGF™ 16-cylinder engine

consisting of:– 30+% increase in BMEP (850kW to 1100kW @ 1,800RPM)– leaner combustion than VGF’s λ=1.5 (24:1) AFR to promote

low NOx and improved BTE,– piston redesign for increased strength, turbulence, mfb10-90

control, and CR increase from VGF’s 11:1.– Timing advanced 7° and 10-90 burn rate reduced 7°– major design changes to engine breathing/induction (Miller

cycle), power cylinder, control systems, while maintaining layout to allow crankcase interchangeability with the VGF, and

– all results in BTE increase of 6 percentage points!

• Ignition system objectives: use current WED spark plug; lower variability on mfb, IMEP, and PCP; extended lean limit, and balanced/acceptable spark plug Vd and tip temperatures to achieve desired service life.

Waukesha

Current LeanCurrent Lean--burn State at WEDburn State at WED• Used successfully at

WED with λ’s of 1.75 and 2.0

• The downfalls– extra initial and

maintenance costs,– potential site boosting of

(and need for) secondary fuel source,

– harsh environment for ignition source,

– increased NOxemissions, and

– a more complex system to optimize for durability and serviceability.

Waukesha

WED LeanWED Lean--burn State Cont’dburn State Cont’d• Open chamber combustion

is cheap and simple, but…– slow burn durations (can be

good) with high variability (bad),

– high PCP variability,– high local flow velocities,

especially as squish heights and CR’s get more aggressive,

– high Vd, and– low lean operating limit.

• A compromise is needed...

Waukesha

Test ApparatusTest Apparatus• 6-cylinder VGF™ engine with various

modifications to run intended conditions– Bore X Stroke: 152 X 165 mm– Displacement: 18 Liters (1,096 in3)– Induction: Turbocharged, Intercooled, Draw-through

• MTS® ADAPT cell data acquisition system• Hi-Techniques Win600 high-speed DAS with

REVelation engine combustion analysis software

• Existing J-type PM spark plug with CD-type ignition system

• All other engine hardware remained fixed

Waukesha

Fixed Prechamber CharacteristicsFixed Prechamber Characteristics• A number of prechamber aspects were

fixed due to schedule constraints:– orifice downward angle with regard to fire deck,– direction of prechamber orifice at bottom-center

of prechamber shield,– quantity of prechamber orifices, and– orifice tangential angle magnitude to cylinder

axis.• Further investigation is necessary to

optimize these for alternative bowl shapes, compression ratios, engine speed, bore size, and spark plug electrode design.

Waukesha

MEPP Literature SearchMEPP Literature Search• Published recommended areas, ratios, and trends for

fueled systems helped to organize and direct testing efforts– Total hole cross-sectional area/ prechamber volume,– Prechamber volume/ cylinder clearance volume,– Total hole cross-sectional area/ prechamber cross-sectional

area, and• Compressed prechamber volume / residual storage

volume (developed during research)– Internal prechamber residuals thought to greatly effect

performance– Total Prechamber Volume/ Effective CR of IVCeff to spark

Measured volume above point of spark initiation– Minimize to enhance lean limits

• More details in ASME publication

Waukesha

Tangential Relationship to SwirlTangential Relationship to Swirl• Affects both fuel entering

and flame jet exiting fluid exchanges

• Nomenclature convention will change with engine

• Published works on fuel oil micropilot of natural gas

• Measurable BTE difference in line with micropilot

• Normal orifices similar to fueled systems resulted in extreme misfire at λ=1.6 (8.5% O2)– Confirms that higher

gas velocities at electrode quench early flame kernel propagation

Parallel-with Counter-to BaselineMFB0-5 14.1 14.1 18.5

σ5 0.64 0.67 1.33MFB0-10 17.5 17.5 23.1

σ10 0.72 0.75 1.59MFB0-50 27.7 27.9 36.2

σ50 1.04 1.05 2.43η 39.5 39.2 38.6

COVIMEP 1.02 0.97 2.341,800 RPM, 16 bar BMEP, 1,800 RPM, 16 bar BMEP, λλ=1.68 =1.68

((9.0% O9.0% O22), and 1 gr./hp), and 1 gr./hp--hr NOhr NOxx timingtiming

Waukesha

Shield Orifice DiameterShield Orifice Diameter• With quantity & location

fixed, this alters cross-sectional area only

• Increased diameter added delay, since decreased pressure differential led to slower main chamber burn

• Combustion variability increased with increasing orifice size, contrary to published works on fueled systems, possibly due to more inconsistent burns from the lower-charged exiting flame jets

Small Medium Large BaselineMFB0-5 14.1 14.8 15.8 18.5

σ5 0.64 0.63 0.69 1.33MFB0-10 17.5 18.4 19.6 23.1

σ10 0.72 0.70 0.79 1.59MFB0-50 27.7 29.2 31.1 36.2

σ50 1.04 1.10 1.25 2.43η 39.5 38.7 38.2 38.6

COVIMEP 1.02 1.00 1.22 2.34σPCP 62.3 63.0 65.7 117.6

COVPCP 4.10 4.23 4.60 8.131,800 RPM, 16 bar BMEP, 1,800 RPM, 16 bar BMEP, λλ=1.68 =1.68

((9.0% O9.0% O22), and 1 gr./hp), and 1 gr./hp--hr NOhr NOxx timingtiming

Waukesha

Shield Orifice DiameterShield Orifice Diameter• Pressure transducers

both at fire deck and spark plug mounted

• As expected, pressure differential increased as orifice diameter decreased– Both during compression

and alternately during the power stroke

0

300

600

900

1200

1500

1800

-30 -20 -10 0 10 20 30Crank angle position (CAD)

Pres

sure

(psi

)

Main chamber

Prechamber

Small Medium LargeMax ∆P during charging 62.2 22.8 18.3

Engine timing for 1 gr. NOx 11° 11.5° 12°∆P at ignition CAD 54.8 18.4 16.6

Waukesha

Prechamber VolumePrechamber Volume• Shield & all else fixed,

but plug recessed• Delay reduced and

efficiency gain with volume increase, but hit on lean limit

• Extreme lean limit attainable only previously by fueled systems

• Lower η can be overcome by final engine design and performance calibrations

= Turbo= Turbo--limited, limited, not misfirenot misfire

Low Middle High BaselineMFB0-5 18.0 14.1 14.4 18.5

σ5 0.58 0.64 0.78 1.33MFB0-10 21.8 17.5 17.5 23.1

σ10 0.74 0.72 0.86 1.59MFB0-50 34.1 27.7 27.6 36.2

σ50 1.32 1.04 1.23 2.43Timing 15° 11° 10° 18°LL (λ) 1.75 1.71 1.73 1.74

η 37.9 39.5 39.0 38.6COVIMEP 1.3 1.0 1.1 2.34

1,800 RPM, 16 bar BMEP, 1,800 RPM, 16 bar BMEP, λλ=1.68 =1.68 ((9.0% O9.0% O22), and 1 gr./hp), and 1 gr./hp--hr NOhr NOxx timingtiming

Waukesha

Prechamber VolumePrechamber Volume• Larger PC volumes

produced quicker burn durations, so ignition delay was not found

• Smaller ∆P’s limit flame jet velocities and main chamber penetration

• Timing retarded to maintain NOx with increase in Vdemand

900

1200

1500

1800

-5 0 5 10Crank angle position (CAD)

Pres

sure

(psi

)

Main chamber

Prechamber

Max ∆P

Low Middle HighMax ∆P -49.8 -239.0 -371.4

CAD @ Max ∆P -4° 0° +1.5°

Timing (BTDC) 15° 11° 10°

Waukesha

Recession of Entire PrechamberRecession of Entire Prechamber• Shield @ fire deck

and 2 non-equal recessed increments

• Measurable ignition delay seen, but expected reduction in lean limit

• Reduced startability due to loss of purging ability of residuals

Low Middle High BaselineMFB0-5 19.7 21.8 25.2 18.5

σ5 0.79 0.98 0.92 1.33MFB0-10 23.69 25.84 29.29 23.1

σ10 0.97 1.14 1.09 1.59MFB0-50 36.25 38.05 41.63 36.2

σ50 1.62 1.74 1.72 2.43Timing 17° 20° 24° 18°LL (λ) 1.81 1.75 1.74 1.74

COVIMEP 1.6 1.5 1.5 2.341,800 RPM, 16 bar BMEP, 1,800 RPM, 16 bar BMEP, λλ=1.68 =1.68

((9.0% O9.0% O22), and 1 gr./hp), and 1 gr./hp--hr NOhr NOxx timingtiming

= Turbo= Turbo--limited, limited, not misfirenot misfire

Waukesha

ConclusionsConclusions• Orifice tangential entrance angle critical to performance of this

system and benefit is seen with exiting flame jets in ‘parallel with’ in-cylinder swirl,

• Increasing orifice diameter slowed main chamber burn and increased variability,

• Increasing prechamber volume resulted in quicker main chamber burn and reduced lean limit,

• Reducing prechamber volume played a key role in extending the lean operating limit and controlling ignition delay,

• Recessing the entire prechamber volume lowered the lean operating limit, although ignition delay was favorably increased,

• Certain aspects of this system are patent pending, • It is possible to achieve ARES phase 1 performance goals

using an existing J-type spark plug as the ignition source (contrary to industry competition), and

• Further information including references may be found in ASME ICEF2004-821.

Waukesha

Questions?Questions?

Waukesha’s APG Enginator™ARES Phase 1

1.1 MW @ 1,800 RPM – 60 Hz (16 bar BMEP) 1 MW @ 1,500 RPM – 50 Hz (17.2 bar BMEP)