emissions control for lean gasoline engines3. production during rich operation and nox reduction...
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ORNL is managed by UT-Battelle for the US Department of EnergyORNL is managed by UT-Battelle for the US Department of Energy
Emissions Control for Lean Gasoline EnginesJim Parks (PI), Todd Toops, Josh Pihl, Vitaly Prikhodko
Oak Ridge National Laboratory
ACE033June 11, 2015
Sponsors: Gurpreet Singh, Ken Howden, and Leo Breton
Advanced Combustion Engines ProgramU.S. Department of Energy
This presentation does not contain any proprietary, confidential, or otherwise restricted information
2 DOE VTO Annual Merit Review – ace033
Project OverviewTimeline
Budget
Barriers Addressed
Collaborators & Partners• FY15: $377k
• FY14: $400k
• FY13: $500k
• General Motors• Umicore• University of South Carolina• University of Wisconsin• Cross-Cut Lean Exhaust
Emissions Reduction Simulations (CLEERS)
• Barriers listed in VT Program Multi-Year Program Plan 2011-2015:
– 2.3.1B: Lack of cost-effective emission control
– 2.3.1C: Lack of modeling capability for combustion and emission control
– 2.3.1.D: Emissions control durability
• Project began in FY12• Project ongoing with annual goals
through 2017
3 DOE VTO Annual Merit Review – ace033
Objectives and Relevance
Enabling lean-gasoline vehicles to meet emissions regulations will achieve significant reduction in petroleum use
• Objective:– Demonstrate technical path to emission compliance that would allow the
implementation of lean gasoline vehicles in the U.S. market. • Lean vehicles offer 5–15% increased efficiency
over stoichiometric-operated gasoline vehicles • Compliance: U.S. EPA Tier 3 (originally Tier 2 Bin 2)
– Investigate strategies for cost-effective compliance• minimize precious metal content while
maximizing fuel economy
• Relevance:– U.S. passenger car fleet is dominated by gasoline-fueled vehicles. – Enabling introduction of more efficient lean gasoline engines can provide
significant reductions in overall petroleum use• thereby lowering dependence on foreign oil and reducing greenhouse gases
EPA Tier 3 Emission Regulations
>70% less NOx
>85% less
NMOG
70% less PM
4 DOE VTO Annual Merit Review – ace033
gasoline95.5%
diesel4.5%
gasoline99.4%
diesel0.6%
cars33.4%
light trucks38.2%
motorcycles0.3%
buses0.9%
Class 3-6 trucks6.0%
Class 7-8 trucks21.1%
Relevance: small improvements in gasoline fuel economy significantly decreases fuel consumption
Lean gasolinevehicles can
decrease US gasoline
consumption by ~13 billion gal/year
• US car and light-truck fleet dominated by gasoline engines • 10% fuel economy benefit has significant impact
– Potential to save 13 billion gallons gasoline annually• HOWEVER…emissions compliance needed!!!
References: Transportation Energy Data Book, Ed. 33 (2012 petroleum/fuel use data)
Fuel Use:Cars
Fuel Use:Lighttrucks
Highway Transportation PetroleumConsumption by Mode
5 DOE VTO Annual Merit Review – ace033
Milestones and Project Goals
FY13 FY14 FY15 FY16 FY17Fuel economy gain over stoichiometric 7% 10% 10% 12% 15%
Total emissions control devices Pt* (g/Lengine) 8 7 6 5 4
* - will use Pt equivalent cost to account for different costs of Pt, Pd and Rh; 5-year average value fixed at beginning of project
• FY2014, Q1: Measure transient NH3 formed from TWC in an TWC+SCR approach on engine
• FY2014, Q2: Characterize performance of Umicore prototype TWC catalysts for NH3production
• FY2014, Q3: Present results at CLEERS Workshop• FY2014, Q4: Define the potential impact of NOx storage components added to TWC
formulations on NH3 production for downstream NOx reduction over SCR catalysts• FY2015, Q2 [SMART]: Determine effect of aging and/or poisoning on TWC NH3
formation through flow reactor experiments• FY2015, Q4: Simulate transient load/speed operation of passive SCR on BMW lean
gasoline engine platform
5-year Average($/troy oz.) Pt-equivalent
Platinum $ 1,504 /troy oz. 1.0
Palladium $ 463 /troy oz. 0.3
Rhodium $ 3,582 /troy oz. 2.4
Gold $ 989 /troy oz. 0.7
Complete
On TrackFurther studies ongoing
In addition to milestones, a set of project goals has been adopted to ensure progression towards goal of low-cost emissions control solution for fuel efficient lean-burn gasoline vehicles
Complete
CompleteComplete
Complete
Further studies ongoing
6 DOE VTO Annual Merit Review – ace033
Approach focuses on catalyst and system optimization of Passive SCR (and LNT+SCR)
TWC
LeanGasolineEngine
Key Principle: system fuel efficiency gain depends on optimizing NH3production during rich operation and NOx reduction during lean operation
Other Core Principles:• Expand range of temperature operation• Materials must be durable to temperature and poisons (S)• Understand Pt group metals utilization to minimize cost
Minimize rich period of lean-rich cycle
Minimize engine out Lean NOx emissions
Add NOx storage for lean NOx storage and rich phase NH3 production
Minimize NH3oxidation (keep
NH3 stored)
Maintain high NOx conversion over
temperature range
Control emissions during lean-rich
transitions
Lean
Maximize engine out Rich NOx emissions
Minimize engine out Rich CO/HC
emissions
Maximize NOx to NH3conversion efficiency
Maximize CO and HC oxidation efficiency
Clean up CO/HC emissions (if needed)
Rich
Minimize engine out Lean NOx emissions
Add NOx storage for lean NOx storage and rich phase NH3 production
Minimize NH3oxidation (keep
NH3 stored)
Maintain high NOx conversion over
temperature range
Control emissions during lean-rich
transitions
Lean
7 DOE VTO Annual Merit Review – ace033
Iterative Bench Reactor + Engine Study Approach
Bench Flow Reactor with cycling and multi-catalyst (close-coupled
and underfloor) capabilitiesBMW 120i lean gasoline engine platform with
National Instruments (Drivven) open controller
Define exhaust conditions
Formulation-dependent TWC performance TWC performance vs. AFR with
realistic HC and H2 characterization
Controlled TWC+SCR system performance Realistic TWC+SCR system performance
with fuel efficiency measurement
TWC+SCR performance with refined load step cycle Combustion parameter optimization to
maximize NH3 production
Collaborations with modeling community and CLEERS
System study guidance
Prototype catalysts
8 DOE VTO Annual Merit Review – ace033
Collaborations and PartnersPrimary Project Partners• GM
– guidance and advice on lean gasoline systems via monthly teleconferences
• Umicore– guidance (via monthly teleconferences) and catalysts for
studies (both commercial and prototype formulations)• University of South Carolina (Oleg Alexeev, Anton
Lauterbach)– Catalyst aging studies with student Calvin Thomas
• University of Wisconsin (Chris Rutland)– modeling of lean emission control systems
Additional Collaborators• CDTi
– catalysts for studies• CLEERS
– Share results/data and identify research needs• LANL
– Engine platform used for NH3 sensor study (see LANL AMR talk ACE079)• MECA
– GPF studies via Work For Others contract• DOE VTO Fuel and Lubricant Technology Program
– Engine platform used for ethanol-based HC-SCR studies (see AMR talk FT007 - Todd Toops)
9 DOE VTO Annual Merit Review – ace033
Responses to 2014 ReviewersApproach: investigating alternatives to urea injection highly appropriate...low temperature limitations of urea based systems are a well-established barrier…nice evolution of understanding and following adjustment of approach…using EGR and other engine means to adjust NOx and potential H2 and/or NH3 production is needed... thorough job in devising a strong framework for the project
Technical Accomplishments: excellent outcome and worthwhile results…large amount of fundamental data displayed here was quite impressive…data appeared robust, but more may be needed in the regards, e.g., repeatability, aging, poisoning effects…investigate novel purge strategies to limit CO production during the rich purges…good correlation between laboratory results and vehicle…DeSOx strategies were critical to enabling this technology to proceed and effect of SO2/SO3 on both the LNT and SCR
Category ScoreApproach 3.80Tech Accomplishments 3.50Collaboration 3.70Future Research 3.60Weighted Average 3.61
Collaborations: excellent inclusion of both suppliers and OEMs…team was extremely strong…impressive
Future plans: anxious to see the aging data…combined TWC/NSC may be important enablers for meeting LEVIII and Tier II Bin 2 standards for lean systems…mixed thoughts on whether to focus on transients versus other key engine drivers like EGR or other engine calibrations…EGR understanding might be better to develop earlier, unless one sees more interesting transient results that can significantly impact the after-treatment fundamentals…need to include purge strategy to limit impact of the rich purges on CO, HC, and fuel economy…important to better understand the PM and HC emissions on the vehicle…keep an eye on N2O
Relevance: 5-10% fuel consumption savings in the 2020 timeframe may cost OEMs about $75 per percent, leaves $500 added cost to a lean burn versus a stoichiometric GDI engine, seems achievable…running lean enhancements…well focused on fuel economy targets.
Funding: if more funds needed to shift some work into the engine approaches, money should be made available, at least enough to get data for a new proposal…not sure why modeling had not been integrated into the tasks
FY2014 AMR Review(5 Reviewers)
[scores: 1 (min) to 4 (max)]
10 DOE VTO Annual Merit Review – ace033
Responses to 2014 ReviewersApproach: investigating alternatives to urea injection highly appropriate...low temperature limitations of urea based systems are a well-established barrier…nice evolution of understanding and following adjustment of approach…using EGR and other engine means to adjust NOx and potential H2 and/or NH3 production is needed... thorough job in devising a strong framework for the project
Technical Accomplishments: excellent outcome and worthwhile results…large amount of fundamental data displayed here was quite impressive…data appeared robust, but more may be needed in the regards, e.g., repeatability, aging, poisoning effects…investigate novel purge strategies to limit CO production during the rich purges…good correlation between laboratory results and vehicle…DeSOx strategies were critical to enabling this technology to proceed and effect of SO2/SO3 on both the LNT and SCR
Category ScoreApproach 3.80Tech Accomplishments 3.50Collaboration 3.70Future Research 3.60Weighted Average 3.61
Collaborations: excellent inclusion of both suppliers and OEMs…team was extremely strong…impressive
Future plans: anxious to see the aging data…combined TWC/NSC may be important enablers for meeting LEVIII and Tier II Bin 2 standards for lean systems…mixed thoughts on whether to focus on transients versus other key engine drivers like EGR or other engine calibrations…EGR understanding might be better to develop earlier, unless one sees more interesting transient results that can significantly impact the after-treatment fundamentals…need to include purge strategy to limit impact of the rich purges on CO, HC, and fuel economy…important to better understand the PM and HC emissions on the vehicle…keep an eye on N2O
Relevance: 5-10% fuel consumption savings in the 2020 timeframe may cost OEMs about $75 per percent, leaves $500 added cost to a lean burn versus a stoichiometric GDI engine, seems achievable…running lean enhancements…well focused on fuel economy targets.
Funding: if more funds needed to shift some work into the engine approaches, money should be made available, at least enough to get data for a new proposal…not sure why modeling had not been integrated into the tasks
FY2014 AMR Review(5 Reviewers)
[scores: 1 (min) to 4 (max)]Comment Area Response
Reviewers complemented approach and accomplishments
Continuing approach and targeting projectgoals
Combustion parameters for optimal emissions control
Extended studies in this area
Interest in aging results Obtained hydrothermal and S aging results (studies ongoing)
Purge, lean-rich transitions, and transient control
Project moving more in this important direction
Modeling Outside of project scope but collaborations with modeling community
11 DOE VTO Annual Merit Review – ace033
Summary of Technical Accomplishments• Completed full characterization on bench flow reactor of Umicore
prototype catalyst matrix– Fixed load cycle vs. load step cycle results– Using more challenging HCs
sample ID Description Pt (g/l) Pd (g/l) Rh (g/l) OSC NSCMalibu-1 Front half of TWC 0 7.3 0 N NMalibu-2 Rear half of TWC 0 1.1 0.3 Y N
Malibu-combo Full TWC 0 4.0 0.16 Y NORNL-1 Pt + Pd + Rh 2.47 4.17 0.05 Y YORNL-2 Pd + Rh 0 6.36 0.14 N NORNL-6 Pd 0 6.50 0 N NORNL-5 Pd + OSC high 0 6.50 0 H NORNL-4 Pd + OSC med 0 4.06 0 M NORNL-3 Pd + OSC low 0 1.41 0 L N
• Performed hydrothermal and S rapid aging of TWC (Malibu-1)– Using industry approved cycle methodology (ongoing)
• Preliminary results obtained from engine out NOx optimization studies– Ongoing studies targeting minimizing rich period of lean-rich cycle
• On engine studies of load step and lean-rich-lean transitions (ongoing)– Focus toward transient operation; details not discussed in this presentation
Catalyst Sample Matrix [OSC=oxygen storage capacity; NSC=NOx storage capacity]
12 DOE VTO Annual Merit Review – ace033
Bench Reactor Formulation Study: TWC formulation affects NH3yield during rich operation, particularly at high temperatures
• Extensive data set: 5 formulations, 7 Ts, 5 λs, 2 conditions, 5 cycles
• Temperature, λ, TWC formulation all impact NH3selectivity
• Working to understand correlations between formulation & selectivity
Malibu1: Pd ORNL6: Pd ORNL5: Pd+OSC
ORNL2: Pd+Rh ORNL1: NSR
λ
λ
Results from fixed-load lean-rich cycles with feedback control based on NH3:NOx [see backup slide 24 for full details]
13 DOE VTO Annual Merit Review – ace033
TWC formulation impacts fuel consumption through NH3selectivity (rich time) and NOx storage (lean time)
Rich Time(NH3 selectivity)
Lean Time(NOx storage)
Fuel Consumption Benefit over stoich operation
Fixe
d Lo
ad C
yclin
g*ric
h: 2
bar
BM
EP, λ
0.97
Load
Ste
p C
yclin
g*ric
h: 8
bar
BM
EP, λ
0.95 w/ NSC
w/ NSC w/ NSC
w/ NSC
bette
r
bette
r
better
*Feedback controlled cycles (cycle average NH3:NOx=1)
Catalysts with
varying PGMs
and OSC
Catalyst with NSC
14 DOE VTO Annual Merit Review – ace033
TWC formulation impacts fuel consumption through NH3selectivity (rich time) and NOx storage (lean time)
Rich Time(NH3 selectivity)
Lean Time(NOx storage)
Fuel Consumption Benefit over stoich operation
Fixe
d Lo
ad C
yclin
g*ric
h: 2
bar
BM
EP, λ
0.97
Load
Ste
p C
yclin
g*ric
h: 8
bar
BM
EP, λ
0.95 w/ NSC
w/ NSC w/ NSC
w/ NSC
bette
r
bette
r
better
*Feedback controlled cycles (cycle average NH3:NOx=1)
Catalysts with
varying PGMs
and OSC
Catalyst with NSC
15 DOE VTO Annual Merit Review – ace033
TWC formulation impacts fuel consumption through NH3selectivity (rich time) and NOx storage (lean time)
Rich Time(NH3 selectivity)
Lean Time(NOx storage)
Fuel Consumption Benefit over stoich operation
Fixe
d Lo
ad C
yclin
g*ric
h: 2
bar
BM
EP, λ
0.97
Load
Ste
p C
yclin
g*ric
h: 8
bar
BM
EP, λ
0.95 w/ NSC
w/ NSC w/ NSC
w/ NSC
bette
r
bette
r
better
*Feedback controlled cycles (cycle average NH3:NOx=1)
Catalysts with
varying PGMs
and OSC
Catalyst with NSC
16 DOE VTO Annual Merit Review – ace033
TWC formulation impacts fuel consumption through NH3selectivity (rich time) and NOx storage (lean time)
Rich Time(NH3 selectivity)
Lean Time(NOx storage)
Fuel Consumption Benefit over stoich operation
Fixe
d Lo
ad C
yclin
g*ric
h: 2
bar
BM
EP, λ
0.97
Load
Ste
p C
yclin
g*ric
h: 8
bar
BM
EP, λ
0.95 w/ NSC
w/ NSC w/ NSC
w/ NSC
bette
r
bette
r
better
• Temperature affects performance dramatically for catalyst with NOx storage component (NSC)
• At low temps, NSC gives greater fuel efficiency; at high temps, Pd-only formulations better
• Combinations of Pd and NSC formulations of interest
*Feedback controlled cycles (cycle average NH3:NOx=1)
Catalysts with
varying PGMs
and OSC
Catalyst with NSC
17 DOE VTO Annual Merit Review – ace033
TWC conversions highlight remaining emissions challenges: lean HC, rich CO
Rich λ=0.97
~2 bar BMEP
Lean λ=2.0
~2 bar BMEP
NOx conversion HC conversion CO conversion
Rich AFR CO control
challenging
Lean HC control challenging at low temps
(C3H8 shown)
Catalysts with
varying PGMs
and OSC
Catalyst with NSC
18 DOE VTO Annual Merit Review – ace033
Aging and Poison Study: Dedicated thermal aging reactor built for industry-approved thermal cycle• Automated aging with TWC located
outside of heated zone
• Lean/Rich/Stoich. controlled through O2 flow rate
• UEGO sensors before and after reactor to ensure proper cycling
• Thermocouple locations:– Gas inlet– Catalyst inlet/midbed/outlet
• Using UEGO and thermocouples, monitor as a function of aging:– Light-off, WGS, OSC
• Age TWCs to 25h, 50h, and 100h
• Post aging, evaluate fully in fully-functional bench reactor– Material characterization at USC
Flow
in Mid OutQuartz Tubes (pre-heat)
Catalyst
gas
Heating Region
Heated Zone InsulatedInsulated
Heated Zone InsulatedInsulated
Phase 1 Phase 2 Phase 3 Phase 4Stoich. 330s Rich 10s Stoich. 10s Lean 10s
880885890895900905910915920
5 5.5 6 6.5
Tem
pera
ture
(°C)
Time (minutes)
In
Mid
Stoichiometric StoichiometricRich LeanStoich.
TWC
CO
CO
2
O2
N2
H2O
UEG
O
UEG
O
MFC inputLabview/CPU
19 DOE VTO Annual Merit Review – ace033
High rich-phase NH3 selectivity remains after thermal aging despite WGS reactivity deactivationExperiment:• Catalyst hydrothermally aged:
Malibu-1 (Pd, no OSC)• Aged 100 hours at 900°C
(simulates lifetime)Minimally Affected by Aging:• NH3 production• HC slip• OSC (at 500°C)Significantly Affected by Aging:• CO slip• TWC light off temperature• WGS reactivity
0
0.2
0.4
0.6
0.8
1
1.2
60 60.1 60.2 60.3 60.4 60.5 60.6 60.7 60.8 60.9 61
Norm
alize
d Δλ
Time (Minutes)
Water-Gas-Shift (WGS) reactivity decreases during first 40 hours aging
40 hours
30 hours 20 hours
10 hours 0 hours
Decreasing WGS
Light-off temperature increases 100°C in first 10-20 hrs
0200400600800
10001200140016001800
0.95 0.96 0.97 0.98 0.99 1.00
PPM
Lambda
CO COC3H8 C3H8NH3 NH3NOx NOx
CO
em
issi
ons
incr
ease
NH3 unaffected at λ < 0.985
Fresh Aged 100h
20 DOE VTO Annual Merit Review – ace033
Impact of sulfur exposure also evaluated for effects on passive SCR
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Before(Avg.)
Rich -SO2
Stoich.- SO2
Lean -SO2
Oxy
gen
Sto
rage
(g/L
)
0%
2%
4%
6%
8%
10%
12%
14%
Before(Avg.)
Rich -SO2
Stoich.- SO2
Lean -SO2
CO
con
vers
ion
OSC at 300°C WGS at 300°C
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
300 400 500 600
C3H
8C
onve
rsio
n
Temperature (°C)
Before
Rich - SO2
Propane conversion post S aging at 300°C,λ = 0.97
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
300 400 500 600
NH
3Yi
eld
Temperature (°C)
Before
Rich - SO2
Ammonia yield post S aging at 300°C, λ = 0.97
Experiment:• Catalyst exposed to S:
Malibu-1 (Pd, no OSC)• Aged w/ 50 ppm SO2 at 300°C
for 4 hours under:– Rich (λ=0.97)– Stoich (λ=1.00)– Lean (λ=2.00)
• deS ramp to 600°C after SMinimally Affected by S:• NH3 production• OSC (at 300°C)Significantly Affected by S:• HC slip during rich conditions• WGS reactivity (at 300°C)
21 DOE VTO Annual Merit Review – ace033
0
5
10
15
20
25
30
25 27.5 30 32.5 35
Engi
ne O
ut N
Ox
(mg/
sec)
Spark Timing (DBTDC)
lambda=0.97lambda=1.00
Adjusting rich spark timing can improve fuel efficiency (but not lean EGR)
OEMRich Period Spark Timing Adjustment:
Goal is more NOx/NH3
2000rpm, 4 bar
Investigated changing EGR level, but no significant effect observed (open throttle causes lack of dP to
push EGR at low loads)
0
5
10
15
20
25
0 10 20 30 40 50 60
Engi
ne O
ut N
Ox
(mg/
sec)
EGR Valve Setpoint (duty cycle in %)
1500rpm, 2bar2000rpm, 4bar
OEM
OEM
Lean Period EGR Adjustment:Goal is less NOx
43% gain in Engine Out NOx= +2.8% gain in fuel efficiency*
(rel. to OEM point) 0%2%4%6%8%
10%
29 35
Fuel
Eff
icie
ncy
Gai
n(v
s. S
toic
h)
Spark Timing (DBTDC)
+2.8%Fuel eff.
OEM
*calculated based on load step cycle and ideal SCR
22 DOE VTO Annual Merit Review – ace033
0%
2%
4%
6%
8%
10%
12%
14%
16%
Fuel
Con
sum
ptio
n Be
nefit
(vs.
Sto
ich.
)
FY13 FY14 FY15 FY16 FY17
Remaining Challenges
0
1
2
3
4
5
6
7
8
9Pt
-Equ
ival
ent (
g/Li
ter e
ngin
e)
FY13 FY14 FY15 FY16 FY17B
etter
Fuel Economy PGM [Cost]
Bet
ter
BMW 120iTWC+LNT
• Improve system level fuel economy (reduce NH3 production fuel penalty)• Address catalyst performance during transients and rich-lean transitions• Determine technique to enable NSC functionality over temperature range • Broaden aging studies to include SCR
max
0
1
2
3
4
5
BMW 120i Passive SCR
Cata
lyst
Vol
ume
(lite
rs)
LNT
TWCTWC
SCR
Size
Bench Flow Reactor StatusEngine-Based Study Status
max
calc
23 DOE VTO Annual Merit Review – ace033
Future Work: Addressing Remaining Challenges
• Catalyst formulation studies on bench flow reactor– Revisit TWC+SCR with new information from prototype catalyst matrix– Combine Pd-based and NSC-containing TWCs to optimize– Examine SCR formulations for NH3 oxidation
• Continue aging studies including studying select prototype formulations– Perform materials characterization (just starting) [TEM, BET/Chemi, XRD]– Continue aging of TWC formulations including with sulfur while cycling– Study aging of SCR
• Continue engine-based studies to maximize system fuel efficiency – Continue spark-timing studies for more efficient NH3 production– Study select prototype TWC formulations on engine– Understand transient and switching effects on Passive SCR/LNT+SCR
24 DOE VTO Annual Merit Review – ace033
SummaryRelevance Enabling lean gasoline vehicles will significantly reduce US
petroleum use
Approach
Focus on non-urea Passive SCR and LNT+SCR
Evaluate catalyst formulations on bench flow reactor for cost-effective emissions control
Study fuel penalty and realistic performance on lean gasoline engine research platform
CollaborationsIndustry: GM and catalyst suppliers Umicore and CDTi
Universities: Univ. of South Carolina and the Univ. of Wisconsin
National Labs: LANL (platform supported NH3 sensor study)
Technical Accomplishments
Completed full characterization on bench flow reactor of Umicore prototype catalyst matrix
Completed hydrothermal and S rapid aging of TWC (Malibu-1)
Preliminary results obtained from engine out NOx optimization studies
Future Work Bench reactor, aging, and engine studies ongoing toward 5-year project goals of fuel efficiency and cost (Pt-equivalent)
25 DOE VTO Annual Merit Review – ace033
Technical Backup slides
26 DOE VTO Annual Merit Review – ace033
BMW 120i engine features three main combustion modes
0
200
400
600
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Inje
ctor
Driv
e Vol
tage
(V) [
data
offs
et b
y 20
0 V]
Crank Angle Degrees (CAD)
Lean Stratified
Lean Homogeneous
Stoich Homogeneous
=Main Spark
=Restrike 1500 rpm, 26% Loadλ=1.9
1500 rpm, 65% Loadλ=1.38
1500 rpm, 31% Loadλ=1.0
• Spray guided combustion system design
• Piezoelectric injectors operate at different voltages as well as different durations
• Multiple sparks enable ignition under lean operation
• In addition to three main combustions modes, there is also an OEM rich homogeneous mode for LNT control of NOX emissions to meet EURO V NOXemission standards
27 DOE VTO Annual Merit Review – ace033
Catalysts Studied in Project• Thanks to Umicore for supplying prototype catalysts (labelled ORNL-x)
• The Malibu catalyst is from an SULEV Chevrolet Malibu commercially available vehicle (represents existing state of the art)
Note: OSC=oxygen storage capacity; NSC=NOx storage capacity
sample ID Description Pt (g/l) Pd (g/l) Rh (g/l) OSC NSC
Malibu-1 Front half of TWC 0 7.3 0 N N
Malibu-2 Rear half of TWC 0 1.1 0.3 Y N
Malibu-combo Full TWC 0 4.0 0.16 Y N
ORNL-1 Pt + Pd + Rh 2.47 4.17 0.05 Y Y
ORNL-2 Pd + Rh 0 6.36 0.14 N N
ORNL-6 Pd 0 6.50 0 N N
ORNL-5 Pd + OSC high 0 6.50 0 H N
ORNL-4 Pd + OSC med 0 4.06 0 M N
ORNL-3 Pd + OSC low 0 1.41 0 L N
28 DOE VTO Annual Merit Review – ace033
Conducted transient flow reactor experiments to estimate TWC effects on fuel consumption• Used feedback-controlled
cycles on flow reactor to evaluate dynamic TWC response in context of passive SCR
• Evaluated two different simulated engine cycles (fixed load, load step)
fixed load load steprich lean rich lean
load (BMEP) 2 bar 2 bar 8 bar 2 bar
SV (h-1) 27000 45000 60000 45000
NOx (ppm) 600 360 1200 360
max lean time 50% 80%simulates cruise “hill” transient
Rich Leanλ 0.95 0.96 0.97 0.98 0.99 1.00 2
O2 (%) 0.96 1.02 1.07 1.13 1.17 1.22 10
CO (%) 2.0 1.8 1.6 1.4 1.2 1.0 0.2
H2 (%) 1.0 0.9 0.8 0.7 0.6 0.5 0
NO (ppm) 600 (or 1200) 360
C3H8 (ppm C1) 3000 1900
H2O (%) 11 6.6
CO2 (%) 11 6.6
TWC SV (hr-1) 27000 (or 60000) 45000
• Compositions & flows selected to mimic BMW GDI engine exhaust
• Space velocity changed with λand load
• C3H8 chosen as challenging HC
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