FuelFuel RequirementsRequirements forfor HCCIHCCI EngineEngine OperationOperation
Tom Ryan Andrew Matheaus Southwest Research Institute
1 HCCIHCCI
l Fuel & Air Charge Undergoes Compression l Spontaneous Reaction Throughout Cylinder l Low Temperature and Fast Reaction Gives Low NOx 2 FundamentalsFundamentals ofof HCCIHCCI ReactionReaction 11
l Ideally, a Homogeneous Fuel-Air Mixture is One in Which the Composition and the Thermodynamic Conditions are Uniform Throughout the Reaction Phase uReaction Starts When the Thermodynamic Conditions are Sufficient to Initiate Chain Branching Reactions uReaction Rates and Reaction Duration are Kinetically Controlled
3 FundamentalsFundamentals ofof HCCIHCCI ReactionReaction 22 l Practical Fuel-Air Mixtures Have Both Compositional and Thermodynamic In-Homogeneities uReaction Begins in the Fuel Richest and the Highest Temperature Locations uReaction Rates and Reaction Duration are Affected by Mixing and Heat Transfer
4 PortPort InjectionInjection ConfigurationConfiguration
l Air-Assist Pressure- Swirl Injector l Timed to Valve Opening l Liquid Drops Acceptable l Evaporation During Compression
5 HCCIHCCI DevelopmentDevelopment ProblemsProblems l SOR Control uNo SOR Property Defined l Mixture Preparation uTotal Evaporation Before the Start of Reaction
6 TypicalTypical HCCIHCCI EngineEngine HeatHeat ReleaseRelease
0.14 6 0.12 0.10 Main Heat Release 0.08 0.06 Inital Heat Release 0.04
0.02 3 1 2 4 5 7
Heat Release Rate (BTU/°) 0.00 Ignition Delay -0.02 75 90 105 120 135 150 165 180 Crank Angle (°)
7 StartStart ofof ReactionReaction EffectsEffects ofof CompressionCompression TemperatureTemperature HistoryHistory
700
650
600
550
500
450
400 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 8 MixtureMixture PreparationPreparation Effects of Intake Temperature
0.7 Diesel, CR=14 0.6 20% Blend CR=14 0.5 40% Blend CR=14 0.4 60% Blend CR=14 80% Blend CR=14 0.3
BSN 0.2 0.1 Bosch Smoke Number 0.0 100 110 120 130 140 150 160 170 180 IntakeIntake Air Air TemperatureTemp. (C) (C) l Slight BSN Advantage With Blends l Critical Temp. For These Conditions 150C l Naphtha & Gasoline Had Zero BSN for All Conditions 9 SORSOR andand MixtureMixture PreparationPreparation Effects of Intake Temperature
185 Diesel, 14 CR 20%, 14 CR 40%, 14 CR 145 60%, 14 CR 80%, 14 CR Gasoline, 16 CR Naphtha, 14 CR 105 Naphtha, 16 CR
65
Intake Manifold Temp. (C) 25 140 145 150 155 Start Of Reaction (CAD)
l All Fuels Advanced SOR Compared to Diesel l Naphtha Operates at Lower Intake Temp. 10 HCCIHCCI RulesRules FuelFuel RelatedRelated l All Fuel Must Be Evaporated Prior to the Start of Reaction uLiquid 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
11 FuelFuel--BlendingBlending withwith TwoTwo FuelingFueling SystemsSystems
Upstream mixing of natural gas
Air-assisted port injection of F-T naphtha
This engine’s fuel system accommodates
one gaseous fuel and one liquid fuel 12 ChoiceChoice ofof FuelsFuels UsedUsed 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 fueling uNatural gas has low reactivity (high-octane number) l F-T naphtha used because: uIt is sufficiently volatile for use with port injection uIts auto-ignition characteristics work with this compression ratio l Other fuels can be used with this engine concept with slight modifications
13 CombustionCombustion PhasingPhasing ControlControl ThroughThrough FuelFuel--BlendingBlending
Intake Air High reactivity Low reactivity More reactive (low-octane) fuel (high-octane) fuel mixture advances combustion Less reactive mixture retards Exhaust combustion
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
14 SingleSingle--FuelFuel HCCIHCCI
Multi-Cylinder Engine on F-T Naphtha 160 l Varying the amount 1000 RPM (approx.) 97 kPa MAP of F-T naphtha Inceasing F-T Naphtha 120 Increasing No Natural Gas changes the F-T Naphtha Amount combustion 80 phasing (when no gas is used)
40 l This is the typical problem
0 experienced with HCCI combustion Heat Release Rate (Arbitrary Units) -40 -30 -20 -10 0 10 20 30 40 of a single fuel Crank Angle Degrees
Typical HCCI combustion phasing advance with increasing load and vice-versa
15 FuelFuel--BlendingBlending ApproachApproach
Mutli-Cylinder Engine on F-TNaphtha and Natural Gas 140 1000 RPM (approx.) 120 97 kPa MAP Increasing Constant Amount of F-T Naphtha Natural Gas 100 Increasing Natural Gas Amount
80
60
40
20
0 No Natural Gas
Heat Release Rate (Arbitrary Units) -20 -40 -30 -20 -10 0 10 20 30 40 Crank Angle Degrees Dual-fuel HCCI combustion phasing is not affected by low-reactivity fuel (natural gas) amount 16 StartStart ofof ReactionReaction EffectsEffects ofof CompressionCompression TemperatureTemperature HistoryHistory
700
650
600
550
500
450
400 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 17 IQTIQT DescriptionDescription l The IQT is a Constant Volume Combustion Bomb Apparatus l The System Includes: uHeated Pressure Vessel uSingle Shot Fuel Injection System uSystem Controller uData Acquisition System
18 IQTIQT PressurePressure VesselVessel andand InjectionInjection SystemSystem
19 IQTIQT PressurePressure VesselVessel
20 IQTIQT FuelFuel InjectionInjection SystemSystem
21 IQTIQT ControllerController andand DataData AcquisitionAcquisition SystemSystem
22 IQTIQT OperationOperation 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
23 IQTIQT RawRaw DataData
24 IQTIQT CNCN CalibrationCalibration l Calibration Shift is Minor l Calibration Checked Daily
25 IQTIQT ApplicationApplication HCCIHCCI FuelFuel RatingRating l Octane Number and Cetane Number were Developed for SI and CI Engine Applications uDevelopments were Evolutionary l HCCI Results Indicate that Neither are Adequate for Reflecting the SOR in an HCCI Engine uData Indicates that some Measure of Autoignition Temperature (AIT) is Needed
uElevated Pressure AIT Defined in IQT 26 EPAITEPAIT MeasurementMeasurement inin IQTIQT
l IQT Used to Measure EHN in FT Diesel Fuel the Elevate Pressure 8
AIT (EPAIT) 7 0 ppm EHN l Tests Done at Different 6
Temperatures 5 l A Fixed Ignition Delay 4 Delay Time, ms 4000 ppm EHN Time is Selected and 3 Used to Define the 2 Ignition Temperature 450 460 470 480 490 500 510 520 530 Temp, oC
27 FuelsFuels TestedTested
12 HEXADECANE l Fuels Tested: 80% HEXADECANE / 20% HEPTAMETHYLNONANE 10 60% HEXADECANE / 40% HEPTAMETHYLNONANE 40% HEXADECANE / 60% HEPTAMETHYLNONANE u ON Reference Fuel 20% HEXADECANE / 80% HEPTAMETHYLNONANE Neat Heptamethylnonane not shown. 24 8 Blends DIESEL 22 80% DIESEL / 20% GASOLINE 60% DIESEL / 40% GASOLINE 40% DIESEL /6 60% GASOLINE u CN Reference Fuel 20 20% DIESEL / 80% GASOLINE GASOLINE 18 Blends 4 16 IGNITION DELAY (ms) u FT Naphtha + EHN 14 2 12 u Gasoline-DF2 Blends 10 IGNITION DELAY (ms) 0 460 470 480 490 500 510 520 530 540 550 8 8 12 TEST TEMPERATURE (oC) 6 0 ppm EHN 500 ppm EHN 80% ISOOCTANE / 20% nHEPTANE 11 60% ISOOCTANE / 40% nHEPTANE 7 1000 ppm EHN 2000 ppm EHN 4 40% ISOOCTANE / 60% nHEPTANE 10 20% ISOOCTANE / 80% nHEPTANE 450 460 470 480 490 500 510 520 530 540 3000 ppm EHN 4000 ppm EHN nHEPTANE o TEST TEMPERATURE ( C) 9 6 ISOOCTANE not shown on this graph. 8
5 7
6 4 5 IGNITION DELAY (ms) IGNITION DELAY (ms)
3 4 3 2 2 28 450 460 470 480 490 500 510 520 460 530 470 480 490 500 510 520 530 540 550 o TEST TEMPERATURE ( C) TEST TEMPERATURE (oC) DataData ConversionConversion
530 l Need Temperature 520 T = 419.3 + 385.5 exp(-0.541 td) 510 at Ignition for C o 500 Different Ignition 490 480 Delay Times Temperature, 470 uSimple Inversion and 460 Regression 450 2.5 3.0 3.5 4.0 4.5 5.0 5.5 l Inverted Data Used Delay Time, ms to Interpolate and FT Additized with EHN Extrapolate to Define a Common Delay
time 29 OctaneOctane NumberNumber vsvs CetaneCetane NumberNumber
120
100
80
60
40 ON = 146 - 3.7*CN
Octane Number 20 + 0.08946*CN2 0 - 0.001263*CN3
10 20 30 40 50 60 Cetane Number 30 EPAITEPAIT vsvs CNCN
Elevated Pressure Autoignition Temperature vs Cetane Number l CN Has Some 650 Relationship to EPAIT
Hexadecane-Heptamethylnonane 600 Isooctane-Heptane DF2-Gasoline l CN Does Not Fischer Tropsch-EHN 550 Universally Relate to
500 EPAIT
450 l ON Relationship is Elevated Pressure Autoignition T 400 Worse Than the CN 0 20 40 60 80 100 120 Cetane Number Relationship
31 EPAITEPAIT vsvs ONON l The ON Relationship is not as Good as 650 Hexadecane-Heptamethylnonane 600 Isooctane-Heptane the CN Relationship DF2-Gasoline Fischer Tropsch-EHN uNegative ON is 550 Possibly Meaningless 500 uMore Deviation with the Additized Fuel 450 Elevated Pressure Autoignition T uShape Inflection 400 Makes Definition of -800 -600 -400 -200 0 200 EPAIT Difficult Octane Number
32 CorrelationCorrelation IQTIQT--EPAITEPAIT DataData andand EngineEngine DataData l SOR in the Engine is 750 Based on the Pre- 700 C)
Reaction o 650 l SOR Predicted using an Arrhenius Type 600
Rate Expression Temp. @ SOR ( 550
uVerified by Engine 500 HRR Measurements 420 440 460 480 500 520 o EPAIT @ 11 ms ( C) l Correlation is Fair
33 FutureFuture ofof HCCIHCCI MethodMethod l Need to Test More Fuels in both the IQT and the HCCI VCR Engine uFollow the IQT Test Method Described uEngine Tests in SwRI VCR Test Engine uTest Fuels: