fuel requirements for hcci engine operationfuel requirements for hcci engine operation fuel...
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Fuel Requirements for HCCI Engine Operation
Fuel Requirements for HCCI Fuel Requirements for HCCI Engine OperationEngine Operation
Tom RyanAndrew Matheaus
Southwest Research Institute
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l Fuel & Air Charge Undergoes Compressionl Spontaneous Reaction Throughout Cylinderl Low Temperature and Fast Reaction Gives Low NOx
HCCIHCCI
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Fundamentals of HCCI Reaction 1Fundamentals of HCCI Reaction 1Fundamentals of HCCI Reaction 1
l Ideally, a Homogeneous Fuel-Air Mixture is One in Which the Composition and the Thermodynamic Conditions are Uniform Throughout the Reaction PhaseuReaction Starts When the Thermodynamic
Conditions are Sufficient to Initiate Chain Branching ReactionsuReaction Rates and Reaction Duration are
Kinetically Controlled
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Fundamentals of HCCI Reaction 2Fundamentals of HCCI Reaction 2Fundamentals of HCCI Reaction 2
l Practical Fuel-Air Mixtures Have Both Compositional and Thermodynamic In-HomogeneitiesuReaction Begins in the Fuel Richest and
the Highest Temperature LocationsuReaction Rates and Reaction Duration are
Affected by Mixing and Heat Transfer
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Port Injection ConfigurationPort Injection ConfigurationPort Injection Configuration
l Air-Assist Pressure-Swirl Injector
l Timed to Valve Opening
l Liquid Drops Acceptable
l Evaporation During Compression
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HCCI Development ProblemsHCCI Development ProblemsHCCI Development Problems
l SOR ControluNo SOR Property Defined
l Mixture PreparationuTotal Evaporation Before the Start of
Reaction
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Typical HCCI Engine Heat ReleaseTypical HCCI Engine Heat ReleaseTypical HCCI Engine Heat Release
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
75 90 105 120 135 150 165 180
Crank Angle (°)
Hea
t Rel
ease
Rat
e (B
TU
/°)
Inital Heat Release
Main Heat Release
Ignition Delay
1 23
4 5
6
7
8
Start of ReactionEffects of Compression Temperature History
Start of ReactionStart of ReactionEffects of Compression Temperature HistoryEffects of Compression Temperature History
400
450
500
550
600
650
700
75 85 95 105 115 125 135 145 155
Crank Angle (°)
•Various Intake Temperatures and EGR
•In All Cases SOR is Very Near 650 K
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Mixture PreparationMixture PreparationEffects of Intake TemperatureEffects of Intake Temperature
l Slight BSN Advantage With Blendsl Critical Temp. For These Conditions 150Cl Naphtha & Gasoline Had Zero BSN for
All Conditions
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
100 110 120 130 140 150 160 170 180Intake Air Temperature (C)
Bos
ch S
mok
e N
umbe
r Diesel, CR=1420% Blend CR=1440% Blend CR=1460% Blend CR=1480% Blend CR=14
BS
N
Intake Air Temp. (C)
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SOR and Mixture PreparationSOR and Mixture PreparationEffects of Intake TemperatureEffects of Intake Temperature
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65
105
145
185
140 145 150 155Start Of Reaction (CAD)
Inta
ke M
anif
old
Tem
p. (C
)Diesel, 14 CR20%, 14 CR40%, 14 CR60%, 14 CR80%, 14 CRGasoline, 16 CRNaphtha, 14 CRNaphtha, 16 CR
l All Fuels Advanced SOR Compared to Diesell Naphtha Operates at Lower Intake Temp.
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HCCI RulesFuel Related
HCCI RulesHCCI RulesFuel RelatedFuel Related
l All Fuel Must Be Evaporated Prior to the Start of ReactionuLiquid Fuel Drops Burn As Diffusion
Flames With High NOx and PM
l Fuels Must Have Start of Reaction Temperatures and Ignition Delay Times (Ignition Characteristics) Such That Reaction Begins at TDC
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Fuel-Blending with Two Fueling Systems
FuelFuel--Blending with Two Fueling Blending with Two Fueling SystemsSystems
This engine’s fuel system accommodates one gaseous fuel and one liquid fuel
Upstream mixingof natural gas
Air-assisted port injectionof F-T naphtha
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Choice of Fuels UsedChoice of Fuels UsedChoice of Fuels Used
l Natural Gas used because:uThis engine was already equipped with fuel
system engine can still be operated at full load on spark-ignited natural gas fuelinguNatural gas has low reactivity (high-octane
number)l F-T naphtha used because:uIt is sufficiently volatile for use with port injectionuIts auto-ignition characteristics work with this
compression ratio
l Other fuels can be used with this engine concept with slight modifications
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Combustion Phasing Control Through Fuel-Blending
Combustion Phasing Control Combustion Phasing Control Through FuelThrough Fuel--Blending Blending
è Premise for this approach: By altering the propensity of the air-fuel mixture to auto-ignite, it is possible to control the combustion phasing
Exhaust
High reactivity(low-octane) fuel
Low reactivity(high-octane) fuel
Intake Air
More reactivemixture advances combustion
Less reactivemixture retards combustion
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Single-Fuel HCCI SingleSingle--Fuel HCCI Fuel HCCI
l Varying the amount of F-T naphtha changes the combustion phasing (when no gas is used)
l This is the typical problem experienced with HCCI combustion of a single fuel
0
40
80
120
160
-40 -30 -20 -10 0 10 20 30 40
Multi-Cylinder Engine on F-T Naphtha
Hea
t Rel
ease
Rat
e (A
rbitr
ary
Uni
ts)
Crank Angle Degrees
Increasing F-T Naphtha
Amount
1000 RPM (approx.)97 kPa MAP
Inceasing F-T NaphthaNo Natural Gas
Typical HCCI combustion phasing advance with increasing load and vice-versa
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Fuel-Blending ApproachFuelFuel--Blending ApproachBlending Approach
-20
0
20
40
60
80
100
120
140
-40 -30 -20 -10 0 10 20 30 40
Mutli-Cylinder Engine on F-TNaphtha and Natural GasH
eat R
elea
se R
ate
(Arb
itrar
y U
nits
)
Crank Angle Degrees
1000 RPM (approx.)97 kPa MAPConstant Amount of F-T NaphthaIncreasing Natural Gas
No Natural Gas
IncreasingNatural Gas
Amount
Dual-fuel HCCI combustion phasing is not affected by low-reactivity fuel (natural gas) amount
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Start of ReactionEffects of Compression Temperature History
Start of ReactionStart of ReactionEffects of Compression Temperature HistoryEffects of Compression Temperature History
400
450
500
550
600
650
700
75 85 95 105 115 125 135 145 155
Crank Angle (°)
•Various Intake Temperatures and EGR
•In All Cases SOR is Very Near 650 K
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IQT DescriptionIQT DescriptionIQT Description
l The IQT is a Constant Volume Combustion Bomb Apparatus
l The System Includes:uHeated Pressure VesseluSingle Shot Fuel Injection SystemuSystem ControlleruData Acquisition System
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IQT Pressure Vessel and Injection System
IQT Pressure Vessel and Injection IQT Pressure Vessel and Injection SystemSystem
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IQT Pressure VesselIQT Pressure VesselIQT Pressure Vessel
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IQT Fuel Injection SystemIQT Fuel Injection SystemIQT Fuel Injection System
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IQT Controller and Data Acquisition System
IQT Controller and Data IQT Controller and Data Acquisition SystemAcquisition System
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IQT OperationIQT OperationIQT Operation
l The Pressure Vessel is Charged with Air at High Pressure and Heated to the Test Temperature
l Fuel is Injected l Needle Lift and Vessel Pressure are
Recorded and used to Determine the Ignition Delay and Other Parameters
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IQT Raw DataIQT Raw DataIQT Raw Data
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IQT CN CalibrationIQT CN CalibrationIQT CN Calibration
l Calibration Shift is Minor
l Calibration Checked Daily
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IQT ApplicationHCCI Fuel Rating
IQT ApplicationIQT ApplicationHCCI Fuel RatingHCCI Fuel Rating
l Octane Number and Cetane Number were Developed for SI and CI Engine ApplicationsuDevelopments were Evolutionary
l HCCI Results Indicate that Neither are Adequate for Reflecting the SOR in an HCCI EngineuData Indicates that some Measure of
Autoignition Temperature (AIT) is NeededuElevated Pressure AIT Defined in IQT
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EPAIT Measurement in IQTEPAIT Measurement in IQTEPAIT Measurement in IQT
l IQT Used to Measure the Elevate Pressure AIT (EPAIT)
l Tests Done at Different Temperatures
l A Fixed Ignition Delay Time is Selected and Used to Define the Ignition Temperature
EHN in FT Diesel Fuel
Temp, oC
450 460 470 480 490 500 510 520 530
Del
ay T
ime,
ms
2
3
4
5
6
7
8
0 ppm EHN
4000 ppm EHN
282
3
4
5
6
7
8
9
10
11
12
460 470 480 490 500 510 520 530 540 550
TEST TEMPERATURE (oC)
IGN
ITIO
N D
EL
AY
(ms)
80% ISOOCTANE / 20% nHEPTANE
60% ISOOCTANE / 40% nHEPTANE
40% ISOOCTANE / 60% nHEPTANE
20% ISOOCTANE / 80% nHEPTANE
nHEPTANE
ISOOCTANE not shown on this graph.
0
2
4
6
8
10
12
460 470 480 490 500 510 520 530 540 550
TEST TEMPERATURE (oC)
IGN
ITIO
N D
EL
AY
(m
s)
HEXADECANE
80% HEXADECANE / 20% HEPTAMETHYLNONANE
60% HEXADECANE / 40% HEPTAMETHYLNONANE
40% HEXADECANE / 60% HEPTAMETHYLNONANE
20% HEXADECANE / 80% HEPTAMETHYLNONANE
Neat Heptamethylnonane not shown.
Fuels Tested Fuels Tested Fuels Tested
2
3
4
5
6
7
8
450 460 470 480 490 500 510 520 530
TEST TEMPERATURE (oC)
IGN
ITIO
N D
EL
AY
(m
s)
0 ppm EHN 500 ppm EHN
1000 ppm EHN 2000 ppm EHN
3000 ppm EHN 4000 ppm EHN
l Fuels Tested:u ON Reference Fuel
Blendsu CN Reference Fuel
Blendsu FT Naphtha + EHNu Gasoline-DF2 Blends
4
6
8
10
12
14
16
18
20
22
24
450 460 470 480 490 500 510 520 530 540
TEST TEMPERATURE (oC)
IGN
ITIO
N D
EL
AY
(m
s)
DIESEL80% DIESEL / 20% GASOLINE60% DIESEL / 40% GASOLINE40% DIESEL / 60% GASOLINE20% DIESEL / 80% GASOLINEGASOLINE
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Data ConversionData ConversionData Conversion
Delay Time, ms
2.5 3.0 3.5 4.0 4.5 5.0 5.5
Tem
pera
ture
, oC
450
460
470
480
490
500
510
520
530
T = 419.3 + 385.5 exp(-0.541 td)l Need Temperature
at Ignition for Different Ignition Delay TimesuSimple Inversion and
Regression
l Inverted Data Used to Interpolate and Extrapolate to Define a Common Delay time
FT Additized with EHN
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Octane Number vs Cetane NumberOctane Number vs Cetane NumberOctane Number vs Cetane Number
Cetane Number
10 20 30 40 50 60
Oct
ane
Num
ber
0
20
40
60
80
100
120
ON = 146 - 3.7*CN + 0.08946*CN2 - 0.001263*CN3
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EPAIT vs CNEPAIT vs CNEPAIT vs CN
Elevated Pressure Autoignition Temperaturevs
Cetane Number
Cetane Number
0 20 40 60 80 100 120
Ele
vate
d P
ress
ure
Au
toig
nit
ion
T
400
450
500
550
600
650
Hexadecane-HeptamethylnonaneIsooctane-HeptaneDF2-GasolineFischer Tropsch-EHN
l CN Has Some Relationship to EPAIT
l CN Does Not Universally Relate to EPAIT
l ON Relationship is Worse Than the CN Relationship
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EPAIT vs ONEPAIT vs ONEPAIT vs ON
l The ON Relationship is not as Good as the CN RelationshipuNegative ON is
Possibly MeaninglessuMore Deviation with
the Additized FueluShape Inflection
Makes Definition of EPAIT Difficult Octane Number
-800 -600 -400 -200 0 200
Ele
vate
d Pr
essu
re A
utoi
gniti
on T
400
450
500
550
600
650
Hexadecane-HeptamethylnonaneIsooctane-HeptaneDF2-GasolineFischer Tropsch-EHN
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CorrelationIQT-EPAIT Data and Engine Data
CorrelationCorrelationIQTIQT--EPAIT Data and Engine DataEPAIT Data and Engine Data
l SOR in the Engine is Based on the Pre-Reaction
l SOR Predicted using an Arrhenius Type Rate ExpressionuVerified by Engine
HRR Measurements
l Correlation is Fair EPAIT @ 11 ms (oC)
420 440 460 480 500 520
Tem
p. @
SO
R (o C
)500
550
600
650
700
750
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Future of HCCI MethodFuture of HCCI MethodFuture of HCCI Method
l Need to Test More Fuels in both the IQT and the HCCI VCR EngineuFollow the IQT Test Method DescribeduEngine Tests in SwRI VCR Test EngineuTest Fuels:<More GTL Products<Petroleum Naphtha Fractions<Additized ON Reference Fuel Blends<Additized Gasolines<Alternative Fuels
uRelate to SOR In the Engine