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Modeling of HCCI and PCCICombustion Processes
Dan Flowers, Salvador AcevesLawrence Livermore National Laboratory
Robert DibbleUniversity of California, Berkeley
Randy Hessel
University of Wisconsin, Madison
Aristotelis BabajimopolousUniversity of Michigan
Work performed under the auspices of the U.S. Department of Energy by University of California,Lawrence Livermore National Laboratory under Contract W-7405-ENG-48.
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Project Overview: HCCI Engines have potential forHigh Efficiency and Low Emissions
Homogenous Charge Compression Ignition (HCCI)engines have many potential advantages:
Very Low NOx Emissions
Very Low Particulate Emissions
High Efficiency
Lower Cost
We apply chemical kinetic modeling and experiments
towards solving technical barriers of HCCI engines: Combustion timing measurement and control
Cylinder-by-cylinder combustion timing control
Startup Fuel air ratio measurement and control
Low Power Density
Hydrocarbon and CO emissions
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Approach: Fundamental and practical understanding ofHCCI by judicious use of modeling and experiments
Develop numerical tools that predict HCCI combustionwith complex fuels in reasonable computational time(hours and days, not weeks and months)
High Resolution CFD
H3C
C CH3
H2C
H3C
CH
CH2O
.O
H2C
C CH3
H2C
H3C
CHH3C
O
HOH3C
CH
H2C
H3C
CH
H2C
OO.
O
OH
Additive 1
Additive 2
Additive 3
Additive 4
H2C
C CH3
H2C
H3C
CH2
O
O.
O
HO
H2C
C CH3
H2C
H3C
C
H3C
O
HO
O
CH3 O.
Additive 5
H3C
CHC
H3C
CH2
Additive 122
O
O
OH
HC
O
O
HO
Additive 103
O
OHO
O.
H3C
C CH3
H2C
H3C
C
H3C
O
CH3 OH
Additive 204
Detailed Chemistry
Engine Experiments
Fundamental
Understanding+
DesignGuidance
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Objective: Modeling and experiments applied totechnical barriers towards practical HCCI engines
Applying multizone detailed chemical kinetics models tounderstanding fundamentals of HCCI operation
Extending and applying multizone modeling tools tohandle non-homogeneous, but HCCI-like,combustion regimes: PCCI, SCCI
Modeling and experiments to understand fundamentaland practical issues in HCCI
HCCI with binary fuel mixtures using Carbon-14 tracing Studying chemi-ionization as a practical means for combustion
timing measurement
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We have long standing partnershipswith industry and academia
Cummins
Currently involved in CRADA partnership
Previous CRADA produced 2 joint papers
Caterpillar
Providing experimental support
Close collaboration on natural gas HCCI
Sandia National Laboratories
Detailed analysis of experimental data, paper
Lund Institute of Technology 3 joint papers, collaboration on analysis
University of Wisconsin
joint work on KIVA analysis
6 joint papers UC Berkeley
joint experimental and numerical work, >20 jointpapers
graduate students obtaining degrees on HCCI U Michigan
PhD research conducted at LLNL
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Our experiments and modeling advance both practicaland fundamental understanding of HCCI and PCCI
Characterized the role of turbulence on HCCIcombustion through multizone modeling
Completed development of Fully Integrated KIVA3V-multizone (KIVA3V-MZ) model for simulation of HCCIand PCCI combustion
Parallelized KIVA3V-multizone (KIVA3V-MZ-MPI)chemistry solver to significantly reduce computationaltime
Developed rugged and low cost combustion timingsensor for HCCI combustion through ion sensing
Investigated fuel and additive effects on HCCIcombustion using C14 tracing of emission sources
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What is the role of turbulence in HCCI engines?
Lund Institute studied HCCI operation in high and low turbulenceengines
These experiments showed that burn durations in higherturbulence configuration were significantly longer
Debate raised about turbulence influence on the ignition process
Lower turbulencepiston crown
Higher turbulencepiston crown
E i t h l b d ti
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Experiments show longer burn durationfor higher turbulence geometry
Our hypothesis: Chemistry timescales are far too rapid to beaffected by local turbulence timescales, thereforeturbulence plays only an indirect role through heat transfer
O M lti h h t f HCCI
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Our Multi-zone approach has proven accurate for HCCIcombustion with wide range of fuels and engine geometries
KIVA3V is run until aspecific Transition point
Multi-zone HCT model usedfor simulating cycle aftertransition point
KIVA Temps mapped one-wayonto multizone HCT
High resolution CFD with detailed chemistry at every
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High resolution CFD with detailed chemistry at everygrid point exceeds capability of todays computers
Possible Approaches:
Few grid points for CFD and Chemistry
Many grid points for CFD, a few grid points for chemistry (Our approach)- works when chemistry and turbulence weakly interact ( e.g. HCCI)
1 Hour
1 Month
1 Decade
1 Day
Kinetics
CFD
Engine Cycle Simulation(single processor)Axisymmetric CFD grid~200 chemical species
Engine Cycle Simulation(single processor)Axisymmetric CFD grid~200 chemical species 1 Year
We have analyzed HCCI operation both low and high
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We have analyzed HCCI operation both low and highturbulence geometries using the multizone approach
Flat crown (60K cells)Square Bowl Crown (400K cells)
Kiva simulations show the flow pushed into the square
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Kiva simulations show the flow pushed into the squarebowl near TDC with high turbulence geometry
Very little change in swirl velocity occurs with flat top
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Very little change in swirl velocity occurs with flat-toppiston geometry during compression
Flat piston Square bowl piston
Substantial recirculation occurs in square-bowl piston
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Substantial recirculation occurs in square-bowl piston,very little with flat-top
Flat piston Square bowl piston
Higher turbulence yields more heat transfer and
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Higher turbulence yields more heat transfer andbroader temperature distribution within the cylinder
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
900 920 940 960 980 1000
temperature, K
massfractionat1Ktemperature
bins
disc, peak heat release at 3 ATDC
square, peak heat release at 3 ATDC
Our multizone model shows that broader temperature
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Our multizone model shows that broader temperaturedistribution explains the lengthening of the burn duration
Heat release rate, flat piston Heat release rate, square bowl
Conclusion: HCCI is dominated by chemical kinetics,
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Conclusion: HCCI is dominated by chemical kinetics,turbulence plays an indirect role through heat transfer
0 2 4 6 8 10 12
0
2
4
6
8
10
12
Burnduration,
CAD
crank angle for peak heat release rate
solid line: experimental
squaredisc
dotted line: numerical
Our Multi-zone approach has proven accurate for HCCI
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Our Multi zone approach has proven accurate for HCCIcombustion with wide range of fuels and engine geometries
But great interest in partially stratified HCCI for bettercontrol and higher power output (PCCI, SCCI)
KIVA is run until aspecific transition point
Multi-zone HCT modelused for simulating cycleafter transition point
KIVA Temps mappedone-way onto multizoneHCT
We extend this model to map between CFD and Multi-
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We extend this model to map between CFD and Multizone detailed kinetic solver throughout the engine cycle
Fully Integrated KIVA and Multi-zone model (KIVA-MZ)
High resolution CFDsolver handles mixing,advection and diffusion
(>10K cells)
Solutions are mapped backand forth between solvers
throughout the cycle
Chemistry handled bymultizone detailed kineticssolver (10-100 zones)
Significant reduction in computational time with
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g pCFD+multizone approach, but
This approach still requires 50-100 chemistry zones Stillcomputationally intensive, esp. with big mechanisms
Multi-zone model is readily parallelized, parallel multizonechemistry solver now implemented within KIVA3V,yields near linear speedup with number of processors
Fully integrated KIVA3V-MZ-MPI handles chemistry
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y g ypart of simulation in parallel
Fluid mechanics still handled with single processor
Chemistry handled with additional processors, chemistry
speedup scales almost linearly with number ofprocessors (up to ~ number of zones)
Process 0
Fluid
mechanicsstep
Processes 1 (N-1)
Zone1 Zone 2 Zone 3 Zone M
High resolution CFD with detailed chemistry at every
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g y ygrid point exceeds capability of todays computers
Possible Approaches:
Few grid points for CFD and Chemistry Many grid points for CFD, a few grid points for chemistry (Our approach)
- works when chemistry and turbulence weakly interact ( e.g. HCCI)
1 Hour
1 Month
1 Decade
1 Day
Kinetics
CFD
Engine Cycle Simulation(single processor)Axisymmetric CFD grid~200 chemical species
Engine Cycle Simulation(single processor)Axisymmetric CFD grid~200 chemical species 1 Year
Parallelizationcan shiftkinetics costdramatically
lower
Simulations were conducted to analyze Isooctane HCCI
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yin the Sandia Engine (Experiments SAE 2003-01-0752)
5.88 mm
(0.2314 in)
5.23 mm
(0.206 in)
9.01 mm
(0.355 in)
0.305 mm
(0.0120 in)
102 mm
(4.02 in)
Our fully integrated KIVA3V-MZ-MPI solver predicts
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pressure very well compared to Sandia experiments
30
40
50
60
70
80
90
-10 -5 0 5 10 15 20
Crank Angle, Degrees
Pre
ssure
(bar)
Phi=0.26 Experiment
Phi=0.20 Experiment
Phi=0.16 Experiment
Phi=0.10 ExperimentPhi=0.26 Simulation
Phi=0.20 Simulation
Phi=0.16 Simulation
Phi=0.10 Simulation
KIVA3V-MZ-MPI emissions predictions are also in good
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agreement with the experiment
010
20
30
40
50
60
70
80
90
100
0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26
phi
FuelCarbonIntoEm
issions
%Fuel C into CO [%] Experiment
%Fuel C into CO2 [%] Experiment
%Fuel C into HC [%] Experiment
%Fuel into OHC [%] Experiment
%Fuel C into HC [%] Simulation
%Fuel into OHC [%] Simulation
%Fuel C into CO [%] Simulation
%Fuel C into CO2 [%] Simulation
Strength of the fully integrated KIVA3V-MZ-MPI solver
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is simulation of non-homogenous HCCI-like processes
Using validated cases as a baseline, simulationsconducted to investigate imposition of stratification oncombustion
High Stratification
Mild Stratification
Uniform
Comparison of equivalence ratio at 35 degrees BTDC (=0.26 Overall)
HC and OHC lower with increased stratification, CO
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higher for some higher stratification conditions
Consistent with experimental observations for early directinjection engines
0
1000
2000
3000
4000
5000
6000
7000
8000
0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26
Phi
CO(ppm)
steep
shallow
uniform
400
600
800
1000
1200
1400
1600
0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26
Phi
HC
orO
HC
(ppm)
steep (HC)
shallow (HC)
uniform (HC)
steep (OHC)
shallow (OHC)
uniform (OHC)
NOx emissions increase due to higher locali l i i h i d ifi i
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equivalence ratio with increased stratification
0
2
4
6
8
10
12
14
0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26
Phi
NOx
(ppm)
steep
shallow
uniform
KIVA3V-MZ-MPI simulation is currently being used toi ti t PCCI ith l di t i j ti
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investigate PCCI with early direct injection
Early Direct injectionusing KIVA spraymodel for diesel fuel
100 zone (with 100processors) simulationwith n-heptane diesel
fuel surrogate
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Summary: We continue to use our simulation capabilitiesto complement HCCI R&D in Industry Nat Labs Universities
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to complement HCCI R&D in Industry, Nat Labs, Universities
We now have the tools to computationally optimize thegeometry, and fuel-air-EGR distributions in HCCI andHCCI-like engines
KIVA3V-MZ-MPI is a computationally efficient andaccurate tool coupling fluid mechanics and detailedchemical kinetics for prediction HCCI
We have extended multizone tools to handle non-homogeneous direct injected PCCI regimes
Experiments, numerical modeling, and other uniquecapabilities applied to fundamental and practical issuesof HCCI
Future Plans: We will continue to develop tools andanalysis to guide HCCI engine design
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analysis to guide HCCI engine design
Continue applying KIVA3V-MZ-MPI to early direct liquidfuel injection PCCI
Apply modeling to support optical engine PCCIexperiments (Dec, Steeper)
Investigate non-homogeneous engine operationtowards higher load and lower HC and CO emissions
Investigate effects of fuels and fuel mixtures on PCCIand HCCI operation
Study practical strategies of combustion timingmeasurement and control for multi-cylinder engines
Recent and Upcoming Publications (1)
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p g ( )
1) Analysis of the Effect of Geometry Generated Turbulence on HCCI
Combustion by Multi-Zone Modeling SAE Paper 2005-01-2134.Collaboration: Lund Inst., U Wisconsin
Highlights: Detailed study of Role of Turbulence in HCCI combustion
2) A Fully Integrated CFD and Multi-zone Model with DetailedChemical Kinetics for the Simulation of PCCI EnginesInternational Journal of Engine Research (in press).
Collaboration: U Michigan, U Wisconsin
Highlights: Development of approach for Fully Integrated Kiva-Multi-zoneDetailed chemical kinetics code for simulation of HCCI and PCCIengines
3) Effect of the Di-Tertiary Butyl Peroxide (DTBP) additive on HCCICombustion of Fuel Blends of Ethanol and Diethyl Ether SAEPaper 2005-01-2135.
Collaboration: UC Berkeley, CAMS(LLNL)
Highlights: Carbon 14 tracing investigating role of ignition enhancingadditives on HCCI combustion with fuel mixtures.
Recent and Upcoming Publications (2)
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4) Experimental and Numerical Investigation of Effect of Fuel on Ion
Sensor Signal to Determine Combustion Timing in HCCI Engines,International Journal of Engine Research (in press).
Collaboration: UC Berkeley
Highlights: Developed ion formation model for HCCI engines for multiple
fuels, verified model with experiments
5) EGR effect on Ion Signal in HCCI Engines, SAE 2005-01-2126.
Collaboration: UC Berkeley
Highlights: Experimental verification of ion formation chemical kinetics forHCCI with high EGR, for conditions ranging from very lean to slightly richconditions
6) Combustion Timing in HCCI Engines Determined by Ion-Sensor:Experimental and Kinetic Modeling, 30th International Symposiumon Combustion.
Collaboration: UC Berkeley, U Heidelberg
Highlights: First application and experimental verification of ion chemicalkinetic mechanism applied to HCCI engines.
Recent and Upcoming Publications (3)
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7) Investigation of HCCI Combustion of Diethyl Ether and Ethanol
Mixtures Using Carbon 14 Tracing and Numerical Simulations,30th International Symposium on Combustion.
Collaboration: UC Berkeley, CAMS(LLNL)
Highlights: Carbon 14 tracing used to investigate sources of emissions
from dual component fuel blends in HCCI engines
8) Spatial Analysis of Emissions Sources for HCCI Combustion at
Low Loads Using a Multi-Zone Model, SAE Paper 2004-01-1910.
Collaboration: SNL, U Wisconsin, UC BerkeleyHighlights: Detailed chemical kinetic analysis of geometry dependent
emissions from an HCCI engine at low loads
9) Analysis of Homogeneous Charge Compression Ignition (HCCI)Engines for Cogeneration Applications, Proceedings of the ASMEAdvanced Energy Systems Division, 2004
Collaboration: Oregon State University
Highlights: evaluation of the multiple advantages of HCCI for CHP
Recent and Upcoming Publications (4)
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10) Thermal Management for 6-Cylinder HCCI Engine: Low Cost,
High Efficiency, Ultra-Low NOx Power Generation, Proceedings ofthe ASME Internal Combustion Engine Division, May 2004
Collaboration: UC Berkeley
Highlights: Characterization of HCCI combustion for stationary power
11) Improving Ethanol Life Cycle Energy Efficiency by DirectCombustion of Wet Ethanol in HCCI engines, Proceedings of the
ASME Advanced Energy Systems Division
Highlights: how HCCI combustion of wet ethanol can greatly improveenergy balance for ethanol production
12) Source Apportionment of Particulate Matter from a Diesel Pilot-
Ignited Natural Gas Fuelled Heavy Duty DI Engine, SAE Paper
2005-01-2034
Collaboration: University of British Columbia
Highlights: C-14 analysis for identification of source of pollutants in a dualfuel engine
Other collaborative activities
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Ongoing participation at MOU meetings with vehicleand engine manufacturers
Invited presentation at SAE HCCI symposium
Invited presentation at ECI Lean CombustionTechnology II workshop
Several publications with National Laboratories andUniversities in US and abroad:
SAE
The Combustion Institute
International Journal of Engine Research