HCCI in a Variable Compression Ratio Engine:Effects of Engine Variables

HCCI in a Variable Compression Ratio Engine:Effects of Engine Variables

Thomas RyanSouthwest Research Institute

HCCI NOx Reduction Base Engine w LPL EGR

BSNOx = 1.6 g/hp-hr, hot-start transient cycle

0%10%20%30%40%50%60%70%80%90%

100%

0 20 40 60 80 100Load Threshold for HCCI, % of Max Power

Perc

ent T

rans

ient

Cyc

le N

Ox

Red

uctio

n

Fixed HCCI NOx Level Varied HCCI NOx Level

Prediction of HD FTP NOx with Various Levels of HCCIPrediction of HD FTP NOx with Various Levels of HCCI

Outline of PresentationOutline of Presentation

BackgroundDescription of Experimental MatrixExperimental ProceduresGraphical AnalysisConclusions

Background - SwRI HCCI ProgramBackground - SwRI HCCI Program

Fifth in the Series of HCCI PresentationsPrediction of the Start of ReactionControl of the Start of ReactionHCCI Fuel RequirementsEngine Heat ReleaseInteraction of Engine and Fuels

Practical Full Time HCCI Operation Will Require Specific HCCI Fuel

Low Octane gasoline

Experimental VariablesExperimental Variables

Engine VariablesIntake Manifold Temperature and PressureExhaust Gas Recirculation LevelCompression Ratio

Fuel Variables (Selection)Boiling Point DistributionCetane/Octane NumberComposition

Test Engine SpecificationsTest Engine Specifications

Bore 96.8 mmStroke 95.3 mmRod Length 166.5 mmDisplacement 702 ccCompression Ratio 7.5:1 to 16.5:1Swirl Ratio Less Than 0.7CombustionChamber

Shallow Dish

Combustion Chamber DesignCombustion Chamber Design

Bowl In PistonShallow DishSquish Area of 51%

Two Valve HeadLow Swirl Ratio

0.7 Swirl NumberIntake Port Fuel Injection

Air Assist Swirl Atomizer

1

10

100

100 1000Pressure (kPa)

Sauter MeanDiameter(µm)D[v,0.9]

D[v,0.1]

D[v,0.5]

Combustion Chamber PhotoCombustion Chamber Photo

Test FuelsTest Fuels

Diesel Fuel (Typical US)Gasoline (Pump Grade 87 RON)Fischer Tropsch NaphthaBlends of Gasoline and Diesel Fuel

Test Fuel PropertiesTest Fuel Properties

PROPERTY FT NAPHATHA DIESEL FUEL GASOLINEHeat of Combustion,

MJ/kgNet 44.3 42.5 32.9*

Gross 47.7 45.3 45.4*Sulfur, mass % 0.0 0.039 .023Specific Gravity 0.7095 0.8485 .7436

IBP, oC 61 187 2950% 141 263 10595% 186 328 188FBP 194 339 201

Carbon, mass % 83.98 86.83 86.74*Hydrogen mass % 15.92 13.24 13.22*

Cetane Number (IQT) 51 43 13

Test MatrixTest Matrix

CR 8 to 16.5:1EGR 0 to 50%A/F 12.5 to 75:1MAT 28 to 220oCMAP 1 to 2.1 BarSpeed 600 to 2000

Test ProcedureTest Procedure

Full Factorial or DOE was not PossibleEngine Warmed UpSpeed SelectedCR FixedVaried A/F, EGR, MAT, and MAPMapped Region of HCCI Operation

Zero Soot (BSN)Less than 25 ppm NOx (revised Recently down to 15 ppm NOx)

NOx Emissions versus A/FNOx Emissions versus A/F

Air Fuel Ratio10 20 30 40 50 60 70 80

NO

x (p

pm)

0

5

10

15

20

25

Definition of TermsDefinition of Terms

Diesel Fuel

CA (Degrees)140 160 180 200

Hea

t Rel

ease

Rat

e (J

/deg

)

-200

20406080

100120140160

Pre-Reaction

Main Reaction

Phasing

Pre-Reaction Start

Main Reaction Start

Diesel Fuel - Gasoline TestsDiesel Fuel - Gasoline Tests

Gasoline Added to Diesel to Affect the Volatility and IgnitionTests at Zero EGR and 14:1 CR

Gasoline Required 16:1 CR

Delay Decreases with Compression Temp

Pre-Reaction Delay versus Compression T

Compression T (K)900 950 1000 1050 1100

Pre-

Rea

ctio

n D

elay

(ms)

0.81.01.21.41.61.82.02.22.42.6

Pre-Reaction Delay - 20% GasolinePre-Reaction Delay - 20% Gasoline

Linear Relationship -Exponential Curve FitRelationships for Other Blends are Similar

Pre-Reaction Delay versus Compression T20% Gasoline in Diesel Fuel

Compression T (K)900 920 940 960 980 1000 1020 1040 1060 1080

Pre-

Rea

ctio

n D

elay

(ms)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

td = -2.4988 + 20.2548 exp-0.0016*T)

Phasing - 20% Gasoline Blend Phasing - 20% Gasoline Blend

Phasing Linearly Related to the Magnitude of the Pre-ReactionAll Blends Demonstrated the Same Trends

Phasing versus Pre-Reaction Heat Release20% Gasoline in Diesel Fuel

Pre-Reaction Heat Release (kJ)1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Phas

ing

(ms)

0.006

0.008

0.010

0.012

0.014

0.016

0.018

0.020

Pre-Reaction Delay - Curve FitsDiesel Fuel-Gasoline BlendsPre-Reaction Delay - Curve FitsDiesel Fuel-Gasoline Blends

Blends all Demonstrated the Same TrendsReactions Appear to be Dominated by the Diesel Fuel

Pre-Reaction Delay versus Compression T

Compression T (K)850 900 950 1000 1050 1100 1150

Pre-

Rea

ctio

n D

elay

(ms)

0.81.01.21.41.61.82.02.22.42.6

20% Blend 40% Blend60% Blend80% Blend

Phasing - Curve FitsDiesel Fuel-Gasoline BlendsPhasing - Curve FitsDiesel Fuel-Gasoline Blends

Phasing versus Pre-Reaction Heat Release

Pre-reaction Heat release (kJ)0.000 0.005 0.010 0.015 0.020 0.025

Phas

ing

(ms)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

20% Blend 40% Blend60% Blend 80% Blend

All Blends Demonstrated Exactly the Same RelationshipsPre-Reaction Delay and Phasing for these Blends Again Demonstrate the Problem with CN

FT Naphtha - HHR ComparisonFT Naphtha - HHR Comparison

Heat Release Rate versus CA FT Naphtha and Diesel Fuel

CA (Degrees)100 120 140 160 180 200

Hea

t Rel

ease

Rat

e (J

/deg

)

-20

0

20

40

60

80

100

120

140

FT has much Larger Pre-Reaction StageFT Pre-Reaction Delay is LongerPhasing is Much ShorterCN of FT is 51 Compared to 43 for DF - CN Problem

FT Naphtha - Delay and PhasingFT Naphtha - Delay and Phasing

Excellent Correlations for Pre-Reaction Delay and PhasingLarge Pre-Reaction and Long Delay Likely to due to Highly Paraffinic Composition of FT

Pre-Reaction Delay versus Compression TFT Naphtha

Compression T (K)700 750 800 850 900 950 1000

Pre-

Rea

ctio

n D

elay

(ms)

0.5

1.0

1.5

2.0

2.5

3.0

td = -4.0435 + 15.8922 EXP(0.0012*t)

Phasing versus Pre-Reaction Heat ReleaseFT Naphtha

Pre-Reaction Heat Release (kJ)0.03 0.04 0.05 0.06 0.07

Phas

ing

(ms)

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Phasing = 2.0719 -14.98*Heat Release

Impact of Pre-ReactionImpact of Pre-Reaction

FTN Demonstrates very Significant Pre-ReactionGasoline Demonstrates Some Pre-ReactionDiesel Fuel Fall Between the FTN and GasolineMethane Demonstrates No Pre-Reaction

How do the Different Fuels Interact in Blends?

Effect of HRR TimingEffect of HRR Timing

Actual Heat Release too EarlyChanged the Start of the Main ReactionHeld Pre-Reaction Magnitude and Phasing Constant

CA Degree300 320 340 360 380 400

Hea

t Rel

ease

Rat

e

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

Indicated Thermal Efficiency

CA of Main HRR Peak350 360 370 380

Indi

cate

d Th

erm

al E

ffici

ency

26

28

30

32

34

36

38

40

ITE=3108.7-32.927CA+0.11CA2-0.0001CA3

Early SOR and Low EfficiencyITE = 27%

Pre-Reaction DelayPre-Reaction DelayAll Fuels

Pre-Reaction Delay versus Compression T at TDCPRD=7.292-5.49E-03*TPRD=9.136-7.68E-03*TPRD=8.261-6.996E-03*TPRD=7.988-6.303E-03*TPRD=8.388-6.675E-03*TPRD=8.238-6.431E-03*TPRD=8.398-6.673E-03*T

Compression T (K)600 700 800 900 1000 1100 1200

Pre-

Rea

ctio

n D

elay

(ms)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20% Gasoline40% Gasoline60% Gasoline80% Gasoline0% Gasoline100% Gasoline (16:1 CR)FT Naphtha

Gasoline, Diesel Fuel and BlendsPre-Reaction Delay versus Compression T at TDC

PRD=7.292-5.49E-03*TPRD=9.136-7.68E-03*T

PRD=7.988-6.303E-03*TPRD=8.388-6.675E-03*TPRD=8.238-6.431E-03*TPRD=8.398-6.673E-03*T

Compression T (K)900 950 1000 1050 1100 1150

Pre-

Rea

ctio

n D

elay

(ms)

0.60.81.01.21.41.61.82.02.22.42.6

20% Gasoline40% Gasoline60% Gasoline80% Gasoline0% Gasoline100% Gasoline (16:1 CR)

Pre-Reaction DelayPre-Reaction DelayAll Fuels

Pre-Reaction Delay versus Compression T at TDCPRD=7.292-5.49E-03*TPRD=9.136-7.68E-03*TPRD=8.261-6.996E-03*TPRD=7.988-6.303E-03*TPRD=8.388-6.675E-03*TPRD=8.238-6.431E-03*TPRD=8.398-6.673E-03*T

Compression T (K)600 700 800 900 1000 1100 1200

Pre-

Rea

ctio

n D

elay

(ms)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

20% Gasoline40% Gasoline60% Gasoline80% Gasoline0% Gasoline100% Gasoline (16:1 CR)FT Naphtha

Gasoline, Diesel Fuel and BlendsPre-Reaction Delay versus Compression T at TDC

PRD=7.292-5.49E-03*TPRD=9.136-7.68E-03*T

PRD=7.988-6.303E-03*TPRD=8.388-6.675E-03*TPRD=8.238-6.431E-03*TPRD=8.398-6.673E-03*T

Compression T (K)900 950 1000 1050 1100 1150

Pre-

Rea

ctio

n D

elay

(ms)

0.60.81.01.21.41.61.82.02.22.42.6

20% Gasoline40% Gasoline60% Gasoline80% Gasoline0% Gasoline100% Gasoline (16:1 CR)

Gasoline

Diesel Fuel

20% Gasoline80% of Difference FTN

More Like DF But Shorter Delays

Pre-Reaction RatioPre-Reaction Ratio

Pre-Reaction Ratio Defined as the Ratio of the Pre to the Total Heat Release

Pre-Reaction Ratio Increases with Increased Pre-Reaction Delay

All Gasoline and Diesel Fuel BlendsPre-Reaction Ratio versus Pre-Reaction Delay

Pre-Reaction Delay (ms)0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

Pre-

Rea

ctio

n R

atio

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

All Gasoline and Diesel Fuel BlendsPre-Reaction Ratio versus Pre-Reaction Delay

Pre-Reaction Delay (ms)0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Pre-

Rea

ctio

n R

atio

0.00

0.05

0.10

0.15

0.20

0.25

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% GasolineFT Naphtha

Pre-Reaction RatioPre-Reaction Ratio

All Gasoline and Diesel Fuel BlendsPre-Reaction Ratio versus Pre-Reaction Delay

Pre-Reaction Delay (ms)0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

Pre-

Rea

ctio

n R

atio

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

Diesel Fuel

Gasoline

20% Gasoline

All Gasoline and Diesel Fuel BlendsPre-Reaction Ratio versus Pre-Reaction Delay

Pre-Reaction Delay (ms)0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Pre-

Rea

ctio

n R

atio

0.00

0.05

0.10

0.15

0.20

0.25

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% GasolineFT Naphtha

FTNPre-Reaction Ratio

4 to 6 X all Other Fuels

Pre-Reaction Ratio Increases with Increased Pre-Reaction Delay

Pre-Reaction Ratio Defined as the Ratio of the Pre to the Total Heat Release

PhasingPhasing

Phasing Related to the Pre-Reaction Heat Release

Larger Pre-Reaction Means Shorter Phasing

All Gasoline and Diesel Fuel BlendsPhasing versus Pre-Reaction Delay

Pre-Reaction Heat Release0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022

Phas

ing

(ms)

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

All Gasoline and Diesel Fuel Blends and FT NaphthaPhasing versus Pre-Reaction Heat Release

Pre-Reaction Heat Release0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Phas

ing

(ms)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

FT Naphtha0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

PhasingPhasing

All Gasoline and Diesel Fuel Blends and FT NaphthaPhasing versus Pre-Reaction Heat Release

Pre-Reaction Heat Release0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Phas

ing

(ms)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

FT Naphtha0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

FTN 33% LessThan Gasoline and 65% Less

Than Diesel

All Gasoline and Diesel Fuel BlendsPhasing versus Pre-Reaction Delay

Pre-Reaction Heat Release0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022

Phas

ing

(ms)

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0% Gasoline20% Gasoline40% Gasoline60% Gasoline80% Gasoline100% Gasoline

Diesel Fuel

Gasoline

20% Gasoline75% of Difference

Larger Pre-Reaction Means Shorter Phasing

Phasing Related to the Pre-Reaction Heat Release

SummarySummary

Pre-Reaction Delay, Pre-Reaction Ratio (Pre-Reaction Heat Release), and Phasing are all ImportantDiesel Fuel Pre-Reaction Delay (PRD) Shorter than Gasoline

Adding 20% Gasoline Increases PRD by 80% of DifferencesFTN Shortest, but Follows Trend of Diesel Fuel

Summary (continued)Summary (continued)

Diesel Fuel Pre-Reaction Ratio (PRR) Larger than Gasoline

Adding 20% Gasoline Reduced the PRR by 75% of the DifferenceFTN has the Largest PRR by 4-6X

Diesel Fuel Phasing Longer than GasolineAdding 20% Gasoline Reduced the Phasing by 80% of the DifferenceFTN has the Shortest Phasing

33% Less than Gasoline and 65% Less than Diesel Fuel

Summary (continued)Summary (continued)

FTN, Diesel Fuel, and Gasoline all Exhibit Pre-Reaction Heat Release

On Average, 4-6 X Diesel Fuel and GasolineDiesel Fuel PRR is Larger than Gasoline

Methane Doesn’t Exhibit Pre-Reaction Heat ReleaseSwRI Used Methane and FTN in a Multi-Cylinder Test Engine (SAE 2001-01-1897)

Multi-Cylinder Engine TestMulti-Cylinder Engine Test

-20

0

20

40

60

80

100

120

140

-40 -30 -20 -10 0 10 20 30 40

Multi-Cylinder Engine on Two FuelsH

eat R

elea

se R

ate

(Arb

itrar

y U

nits

)

Crank Angle Degrees

1000 RPM (approx.)97 kPa MAPConstant Amount of Reactive FuelIncreasing Non-Reactive Fuel

Straight Reactive Fuel

Increasing Non-Reactive Fuel

PRD and PRR not Affected by the Presence of the Methane, but Main HRR Delayed by Methane

HypothesisHypothesis

Gasoline -FTN Blends will Provide Options for Control of the Ignition and Reaction Processes

FTN is the Reactive Component Gasoline will Affect the PRD, the PRR, and the Phasing of the Blend20/80 Blend of FTN in Gasoline is Proposed

Gasoline will Inhibit the PRD of the FTNLarge PRR of FTN will Decrease the Phasing of the Gasoline

Why 20/80 BlendWhy 20/80 Blend

Alamo_Engine (SwRI Cycle Simulation Code) used to Compute the Compression Temperature History in the Test Engine Operating at Equivalent Diesel Full Load Conditions:

25:1 Air-Fuel Ratio3 Bar Boost10% EGR

Baseline Engine ResultBaseline Engine Result

Parameter ValueMAP (kPa) 300

Fuel Flow Rate(kg/s)

0.00114

Fresh Air FlowRate (kg/s)

0.0292

Torque (N-m) 108.7Indicated Power

(kW)21.76

Indicated ThermalEfficiency

44.2

BSFC ((g/kW-hr) 195.1

Computed TDC Compression T = 860K

Performance Prediction 20/80 BlendPerformance Prediction 20/80 Blend

Used the Relationships Shown AboveAt 860K

PRD – FTN = 2.24– Gasoline = 2.57

PRR– FTN = 0.154– Gasoline = 0.048

Phasing– FTN = 1.79 ms– Gasoline = 1.61 ms

Assumed Gasoline Affects FTN Same as Diesel Fuel, at 1800 rpm, 3 Bar MAP, 95% Combustion Efficiency

Pre SOR at 19o BTDC, Main SOR at 1.1o BTDC, Pre Heat Release = 0.334kJ and Main = 2.76 kJ

Heat Release Rate

0.00

0.50

1.00

1.50

2.00

2.50

3.00

-20 -15 -10 -5 0 5 10CAD (deg aTDC)

HR

R (k

J/C

AD)

Thermal Efficiency = 40%

Thank You.Thank You.

Tom Ryantryan@swri.edu