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2011 DOE Merit Review - 1MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
A University Consortium on Efficient and CleanHigh-Pressure, Lean Burn (HPLB) Engines
University of Michigan (UM):Dennis N. Assanis (PI),
Aris Babajimopoulos, Stani V. Bohac, Zoran S. Filipi, Hong G. Im, George A. Lavoie, Margaret S. Wooldridge
Massachusetts Institute of Technology (MIT):Wai Cheng
University of California, Berkeley (UCB):Jyh-Yuan Chen, Robert Dibble
May 11th, 2010
DOE Project DE-EE0000203This presentation does not contain any proprietary, confidential, or otherwise restricted information
2011 DOE Merit Review - 2MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Overview
• TIMELINE– Start - Oct 2009– Finish – Dec 2012– 50% completed
• BARRIERS ADDRESSED– Improved fuel economy in
light duty gasoline engines– Fundamental knowledge of
advanced engine combustion
• BUDGET– Total project funding - $3,000k– Rec’d FY10 - $1,000k– Rec’d FY11 - $ 500k
• PARTNERS– Universities – UCB, MIT– Collaborations – SNL, LLNL,
ORNL, ANL– Industrial – GM, Conoco-
Phillips, BP, Ford
2011 DOE Merit Review - 3MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
20
30
40
50
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
η _B
rake
(%)
Φ' = Φ (1-RGF)
etaB_v_Phi_prime_TC50_AIR_EGR160
200
240
280
320
BSFC(g/kWh)
1.5Pin (bar) = 1.0
3.0
AIREGR
GT-Power simulation*
DILUTION
BOOST
Objectives and Relevance
DOE VTP Technical Target:• Demonstrate path to achieve 45% peak
engine efficiency with 25 - 40% potential vehicle fuel economy (FE) gain
Project Objectives:Explore advanced dilute, high pressure combustion modes and fuel properties as enablers to achieve FE targets
- Develop analytical link between engine combustion results and potential in-vehicle FE gains
- Investigate benefits of stratification- Explore multi-mode combustion: Spark Assisted Compression
Ignition (SACI), and Microwave Assisted Spark Plug (MWASP)- Determine potential of novel fuel properties for improved FE
A
B
* GT=Power simulation includes: heat transfer, friction, CR = 12, and constant B10-90 = 25 °, CA50 = 10 °ATC
2011 DOE Merit Review - 4MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Approach
• Task 1: System and FE analysis tools– Establish link between advanced combustion modes and potential vehicle FE gains
with GT-power and Matlab simulations (UM)
• Task 2: Stratification as a means to control combustion– Carry out experiments in RCM and gasoline fueled boosted diesel (MIT)– Apply numerical modeling to study turbulent autoignition modes (UM)
• Task 3: Multi-mode combustion– Conduct engine experiments on SACI in FFVA DI engine (UM)– Use CFR engine to test combustion limits with MWASP (UCB)– RCM and Optical Engine experiments on SACI (UM)– Use 1-D modeling of laminar flames in high preheat, high dilution mixtures to
develop correlations for multi-dimensional models– Develop CFD model of SACI with KIVA (UM)
• Task 4: Fuel properties for optimum FE– Explore low octane and other gasoline based fuels in FFVA engine (UM)– Gather fundamental ignition and kinetic data for alternate fuels in RCF (UM)
2011 DOE Merit Review - 5MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Consortium Experimental FacilitiesUM optical engine(SACI and fuels)
UM diesel engine(fuels)
MIT rapid compressionmachine (fuel ignition)
UM camless FFVA engine(multi-mode combustion)
UCB CFR engine(MWASP)
UM RCF(ign. chemistry)
MIT boostedDiesel (stratification)
2011 DOE Merit Review - 6MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Technical Accomplishments (highlights)
• Task 1: System and FE analysis tools– Thermodynamic analysis shows engine efficiency benefits of HPLB (UM)– Vehicle FE framework shows potential vehicle-level gains with HPLB strategy (UM)
• Task 2: Stratification as a means to control combustion– Stratification moderates heat release rate for gasoline HCCI (MIT)– Identified combustion modes with thermal stratification using DNS tools (UM)
• Task 3: Multi-mode combustion– SACI extends high load limit in fully flexible valve actuation (FFVA) engine (UM)– Microwave-Assisted Spark Plug (MWASP) extends lean limit (UCB)– Developed laminar flame speed (SL) correlations for SACI conditions (UM)– Developed CFD model of SACI using new laminar flame speed correlations (UM)
• Task 4: Fuel properties for optimum FE– Low octane fuel extends HCCI high load limit in FFVA engine (UM)– New RCF data obtained on the ignition characteristics of n-butanol (UM)
2011 DOE Merit Review - 7MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 1: Thermodynamic Analysis Shows Engine Efficiency Benefits of HPLB (UM)
• Objective: determine thermodynamic conditions for best FE
• Approach: Use GT-Power model with ideal T/C and fixed burn duration
• Results:– Optimal boosting strategy increases fuel-to-
charge equiv. ratio (Φ’) as boost is increased– Best overall engine efficiency occurs under
highly dilute, high pressure conditions, i.e. advanced combustion
– Peak brake engine efficiency ~ 42%– BSNOx < 0.26 g/kWh up to 18 bar BMEP
• Future Work: – Refine analysis with realistic combustion and
T/C constraints; apply simple aftertreatment constraints (TEX) for HC, CO emissions
– Link FE projections to experimental data in Tasks 2, 3, and 4.
INT EXH
I.C.
EGR
C TηC
ηmech
ηT
GT-Power model- CR = 12; RPM = 2000- Ideal T/C; Eff.=50%- B10-90 (25°)- CA50 (10°ATC)- heat transfer, friction- 2-zone NOx model
HCCI ADV.COMB
SI
20
30
40
50
0 10 20 30 40
η_br
ake
(%)
BMEP (bar)
1.01.5
2.0 2.5 3.0
P_in (bar)
etab_v_bmep_AIR_TC50_EIVC_Throt
Φ = 1Throttled
0.3
0.4
0.5 0.6 1.0Φ’
2
3
1
AIR DILUTION; T/C Eff. = 50%
Φ’ = Φ (1-RGF)
2011 DOE Merit Review - 8MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 1: Low NOx Emissions Are Achievable with Optimum Boosting Strategy
• Optimum boosting strategy and T/C efficiency of 50% result in BSNOx < 0.26 g/kWh
– Up to 18 bar BMEP (Air dilution)
– Up to 25 bar BMEP (EGR dilution)
– Peak ηbrake ∼ 42%
20
30
40
50
0.0
1.0
2.0
3.0
0 10 20 30 40
η_br
ake
(%)
BSN
Ox
(g/k
Wh)
BMEP (bar)
etab and BSNOx_v_bmep_TC50 AIR_EGR_2axes
NOx limit
AIREGR
Turbocharger Efficiency = 50%
2011 DOE Merit Review - 9MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
1
1.1
1.2
1.3
1.4
1.5City-Hwy
Rel
ativ
e FE
SI-NA ADV-NA ADV-boost
1.5
1.4
1.3
1.2
1.1
1.0
Task 1: Vehicle FE Framework Shows Vehicle Level Gains with HPLB Strategy (UM)
• Objective: Provide projection of vehicle FE gains achievable with advanced combustion
• Approach: combine GT-Power generated BSFC maps of 3 ideal engine strategies (previous slide) with Matlab drive cycle simulation
• Results:– 1 → 2 dilution (N. A.) ~ 25% gain
(assumes optimum combustion at all points, and 100% comb. Efficiency)
– 2 → 3 dilution + boosting + downsize ~ 50% gain (assumes T/C eff = 50%)
• Future Work:– Include more realistic combustion
characteristics and constraints
Mid-Size Sedan,3285 lb
Engine Speed (rpm)
Eng
ine
BM
EP
(bar
)
1000 2000 3000 4000 5000 60000
2
4
6
8
10
12
NA - 3.3L
Φ=1Throttled
Engine Speed (rpm)
Eng
ine
BM
EP
(bar
)
1000 2000 3000 4000 5000 60000
2
4
6
8
10
12
NA - 3.3L
AIRdilute
Engine Speed (rpm)
Eng
ine
BM
EP
(bar
)
1000 2000 3000 4000 5000 60000
5
10
15
20
25
BOOSTED – 2.2L
AIRdilution
* Circled numbers refer to engine combustion strategies on earlier slide
2
3
1 *
*
2011 DOE Merit Review - 10MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 2: Stratification Moderates Heat Release Rate for Gasoline HCCI (MIT)• Objective: investigate benefits of
interaction between gasoline fuel properties and stratification
• Approach:– Obtain fuel ignition data in RCM– Vary injection characteristics in
boosted diesel engine to vary stratification
• Results:– Correlation developed for τIGN in RCM– In engine, late injection (90° ABDC) is
effective in setting up stratification by moderating heat release rate
• Future work:– Connect RCM results with engine data– Vary fuel properties 0
1
2
3
4
5
6
0 2 4 6 8
Knoc
k in
dex
(MW
/m2 )
NIMEP (bar)
Gasoline: Pinj=500 bar; Tin=60oC; MAP=1.5 bar
inj 30deg bbdc
inj 30deg abdc
inj 90 abdc • Later injection• Incr. Stratification
Kno
ck In
dex
(MW
/m2 )
1.1 1.2 1.3 1.4 1.51
1000/(T[K])
800 750 700 650 600Temperature [K]
t / τ
−τ = τ = Φ1.5 0.3d d(x 0) (1-x )
1.0
0.8
0.6
ΦDilution
0.0 0.2 0.4
RCM Data(Gasoline)
2011 DOE Merit Review - 11MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 2: Identified Combustion Modes with Thermal Stratification Using DNS Tools (UM)
• Objective: characterize ignition regimes in thermally stratified HCCI combustion
• Approach: Use Computational Singular Perturbation (CSP) analysis of timescales in a reacting flow field to determine Importance Index
(Shows relative importance of deflagration / flame vs. autoignition)
• Results:– Turbulent stratified combustion
invokes multiple reaction modes• Future work:
– Application of method to higher hydrocarbon fuels
– Compositional stratification
T)Convection(T
TDiffusion)(T
Tslowslow
III −− +=
2 D - DNS simulation (H2-Air)Deflagration
1.0
H: Homogeneous kernel, F: FrontS: Spontaneous Ignition, D: Deflagration
IT
TI
0.0
HD
HS
FD FS
SpontaneousIgnition
0.0
In Collaboration With Mauro Valorani, University of Rome, La Sapienza
M = 1 contour in black [denotes active reaction zone]
2011 DOE Merit Review - 12MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 3: SACI Extends High Load Limit in Fully Flexible Valve Actuation (FFVA) Engine (UM)
• Objective: demonstrate load extension with spark assist
• Approach:– Increase load by adding fuel and reducing
trapped residual gas (NVO) with Φ= 1 (increase fuel-to-charge Φ’)
– Control phasing with spark timing
• Results:– Heat release rate moderated by SACI– Maximum load increased to 7.3 bar– Encountered SI knock at highest loads
• Future Work:– Explore variations in proportion of flame vs.
autoignition heat release.– Extend work to higher pressures (cell
upgrade in progress to provide boost)-40 -20 0 20 40 60
0
10
20
30
40
50
60
Crank Angle (deg)A
HR
R (J
/CA
)
4.93 bar5.96 bar6.59 bar6.89 bar7.31 bar
0
200
400
600
800
1000
0 5 10 15
NM
EP
[kP
a]
CA50 [°ATC]
Φ’0.7
0.5
0.3
SparkAdv.
SACI
HCCI
Incr. load
AHR
R (J
/CA)
CA (°ATC)
CA50 = 10°ATC
Manofsky, L., Vavra, J., Babajimopoulos, A., and Assanis, D. (2011) Bridging the Gap between HCCI and SI: Spark-Assisted Compression Ignition. SAE Technical Paper 2011-01-1179
2011 DOE Merit Review - 13MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 3: Microwave-Assisted Spark Plug (MWASP) Extends Lean Limit (UCB)
• Objective: Evaluate the potential benefits of MWASP for advanced combustion modes
• Approach: – Use CFR engine (CR = 7, 9) to test
ignition under lean limit conditions– Model ignition with simplified methane
kinetics and electron gas dynamics• Results:
– Lean limit extension observed– Modeling suggests benefit may
decrease at higher pressures• Future Work:
– Extend experiments into SACI range (higher CR, leaner, and more preheat)
Kinetic model of ignition in a WSRshows effect of energy deposition mode
10 atm 1 atm50 atm
gas (thermal)MW (electronic)
none
lean limitextensionSI
MWASP
MODEOF ENERGY DEPOSITION
Nor
mal
ized
Fue
l Con
sum
ptio
nTe
mpe
ratu
re (K
)
Time (s)
λ
DeFilippo, A., Saxena, S., Rapp, V.H., Ikeda, Y., Chen, J-Y, Dibble, R.W., (2011) Extending the lean flammability limit of gasoline using a microwave assisted sparkplug, SAE Paper no. 2011-01-0663
2011 DOE Merit Review - 14MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 3: Developed Laminar Flame Speed (SL) Correlations for SACI Conditions (UM)• Objective: Understand fundamental
flame behavior and properties for highly preheated, highly dilute mixtures
• Approach:– Use transient flame code HCT to build
dataset of flame properties in SACI regime where experimental data is limited
– Build mathematical correlations for use in turbulent combustion models
• Results:– Viable flames predicted in regions where
SACI observed– Correlations made for AIR and EGR dilute
flames
• Future Work: – Validate vs. images from optical engine
and in RCF
EXPT
HCT dataset lines ofconstant SL
40 bar
Isooctane Flames
( ) ( )10
02 , 01 exp
nD m u b
L EGR f ub u
T T TS D Y FY G TT T T
− = − Φ − −
AIR onlyEGR (O2 term)
Form of correlation shows Air and EGR dependence
Middleton, R.J. et al., “A Computational Study and Correlation of Premixed Isooctane Air Laminar Reaction Front Props. with Combustion Products,” In Preparation.
TB (K)
TU (K)
2011 DOE Merit Review - 15MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 3: Developed CFD Model of SACI Using New Laminar Flame Speed Correlations (UM)
• Objective: develop CFD model of SACI and use to explore possible benefits
• Approach: combine laminar flame speed correlations with models of coherent flamelet and multizone autoignition (CFMZ model)
• Results:– Model compares well with images obtained in
UM optical engine– Good qualitative agreement with heat release
curves in metal engine
• Future work:– Perform parametric studies on variables
affecting heat release partition between flame and autoignition and sensitivity to spark timing
– Validate limits vs. metal engine data
KIVA-CFMZ MODEL EXP
BURNEDGAS
FLAME
UNBURNED (AUTOIGNITION)
Spark
Autoignitionbegins
OpticalEngineImages
Martz, J. B., (2010) , Simulation and Model Development for Auto-Ignition and Reaction Front Propagation in Low-Temperature High-Pressure Lean-Burn Engines , Ph. D. Thesis, University of Michigan, October 2010.
2011 DOE Merit Review - 16MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
275
300
325
350
375
400
425
450
475
-2 0 2 4 6 8 10 12 14
GIM
EP [k
Pa]
CA50 [°ATC]
NVO and Fueling Sweep for Certification Gasoline (RD387)
275
300
325
350
375
400
425
450
475
-2 0 2 4 6 8 10 12 14
GIM
EP [k
Pa]
CA50 [°ATC]
NVO and Fueling Sweep for NH40 (40% n-Heptane, 60% RD387)
Task 4: Low Octane Fuel Extends HCCI High Load Limit in FFVA Engine (UM)
• Objective: Explore ways to use fuel properties to increase HCCI load limit
• Approach:– Use NVO in FFVA engine to provide control
over combustion phasing– Inlet temperature = 45°C– Initially compare gasoline vs. a low octane
surrogate NH40 (40% n-heptane in gasoline)
• Results:– NH40 had higher load limit possibly because
it had faster 10-90 burn duration and could be retarded more without instability
• Future Work:– Expand range of test fuels– Explore benefit of spark assist
Gasoline (RD387); RON = 91
NH40 (40% n-C7H16 / 60% RD387); RON = 53
RI lmit5 MW/m2
RI lmit5 MW/m2
COVIMEP5%
COVIMEP5%
INCR. FUELING
INCR. FUELING
2011 DOE Merit Review - 17MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Task 4: New RCF Data Obtained on the Ignition Characteristics of n-butanol (UM)
• Objective: Investigate ignition of alternative fuels such as n-butanol as a possible infrastructure compatible fuel and blending component for bio-fuels
• Approach:– RCF provides ignition delay data– Sampling system gives intermediate species
data– Both data are necessary to quantify the impact
on fuel reactivity and exhaust emissions• Results:
– Measured ignition delays are in excellent agreement with Black et al. model
– RCF speciation data identify weaknesses in reaction pathways important for predicting and mitigating emissions
• Future work:– Study fuel blends using RCF and optical engine
UM RCF data forP ≅ 3.0 atm
SAMPLING SYSTEM
model resultssampling
experiments
ethene
model results
2011 DOE Merit Review - 18MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Future Work FY11-12
• Task 1: System and FE analysis tools– Refine analysis of optimum combustion strategy with realistic combustion constraints and
turbocharger characteristics. Apply simple TEX constraint for CO, HC aftertreatment. Explore tradeoff between CR and T/C efficiency.
– Link FE projections to experimental data from Tasks 2, 3, and 4.
• Task 2: Stratification as a means to control combustion– Connect RCM ignition results with engine timing data; vary fuel properties– Apply Computational Singular Perturbation (CSP) method to higher hydrocarbon fuels and
compositional stratification
• Task 3: Multi-mode combustion– Explore variations in partition of flame vs. autoignition heat release in SACI in FFVA engine– Extend FFVA SACI work to higher pressures (cell upgrade in progress to provide boost)– Extend MWASP experiments into SACI range (higher CR, leaner, and more preheat)– Compare flame front model results vs. experimental images in optical engine and RCF– Use CFMZ model of SACI to investigate variables affecting details of heat release; sensitivity to
spark timing; and nature of limits by comparison to metal engine data.
• Task 4: Fuel properties for optimum FE– Expand range of test fuels, and include spark assist in testing– Carry out RCF studies of ignition properties of fuel blends
2011 DOE Merit Review - 19MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Collaborations and Coordination
• Working on boosted single cylinder HCCI studies with GM• Working with Microwave Enhanced Ignition device supplied by Yuji Ikeda, Imagineering,
Inc., Japan • Collaborating on SACI and combustion stability with Robert Wagner (ORNL)• Supplied engine maps for HCCI to Argonne National Labs• Currently working with Ford on the next steps towards changing our optical engine to
direct injection.• Working with Chevron on enhancing the effectiveness of stratification on controlling LTC
heat release with fuel (MIT)• Studying sensitivity of spark-assisted HCCI engines to range of market fuels; with BP and
Ford (MIT)• Working with Jacqueline Chen (Sandia National Laboratories), Ramanan Sankaran
(ORNL), Mauro Valorani (University of Rome, La Sapienza), Chris Rutland (UWisc) on mixing effects on HCCI combustion.
• Collaborated with C. K. Westbrook and Bill Pitz (LLNL) on validating reaction mechanisms for long chain alkanes, small esters – now working on alcohols
• Working with Marco Mehl (LLNL) to apply new surrogate fuel kinetics to engine models
2011 DOE Merit Review - 20MITUCBUM
HPLBUniversityConsortium
Project ID: ACE019
Summary
• Task 1: System and FE analysis tools– Thermodynamic analysis confirms HPLB strategy; BTE of 42% with BSNOx < 0.26 g/kWh– System framework developed for vehicle FE assessment: demonstrated potential vehicle level
impact of boosted dilute strategies
• Task 2: Stratification as a means to control combustion– Initial experiments carried out with stratified gasoline fueled diesel engine show stratification
moderates heat release rate– DNS simulation showed multiple combustion/ignition modes in thermally stratified mixture
ranging from spontaneous ignition to deflagration front
• Task 3: Multi-mode combustion– SACI extends high load limit in naturally aspirated FFVA engine– MWASP ignition extends lean limit under NA conditions with potential gains for LTC combustion– Laminar flame correlations developed for high dilution / high preheat conditions– CFD model of SACI developed; good qualitative agreement with optical engine images
• Task 4: Fuel properties for optimum FE– Studies of low octane gasoline fuel shows potential for higher load operation in FFVA (NVO
enabled) HCCI operation– Initial studies on ignition of n-butanol carried out in RCF; speciation results show need for
improvements to kinetic models