Update on Lean Gasoline NOx control at ORNL...2 Acknowledgements •Funding & guidance from DOE VTO...
Transcript of Update on Lean Gasoline NOx control at ORNL...2 Acknowledgements •Funding & guidance from DOE VTO...
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Update on Lean Gasoline NOx control at ORNL
Vitaly Y. Prikhodko, Todd J. Toops , Josh A. Pihl, Calvin Thomas, and James E. Parks II
Oak Ridge National Laboratory
2019 CLEERS WorkshopAnn Arbor, MISeptember 19, 2019
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Acknowledgements
• Funding & guidance from DOE VTO Program Managers:– Ken Howden, Gurpreet Singh, Mike Weismiller
• Collaboration with University of South Carolina:– Calvin Thomas (now at ORNL), Prof. Jochen Lauterbach
• Collaboration with partners at GM:– Wei Li, Lei Wang, Pat Szymkowicz, Arun Solomon, Paul Najt
• Collaboration with partners at Umicore:– Ken Price, Ryan Day, David Moser, Sanket Nipunage, Tom Pauly
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Gasoline engines represent the largest opportunity for reducing petroleum consumption in the U.S.
cars19.1%
light-trucks23.5%
heavy-trucks15.2%
motorcycles0.2%
buses0.5%
non-highway9.4%residential
3.1%
commercial2.6%
electric utilities0.7% industrial
25.8%gasoline
99.4%diesel0.6%
gasoline95.5%
diesel4.5%
Ref: Transportation Energy Data Book, Ed. 36.1, 2018 (2015 data)
• Transportation accounts for 70 % of total petroleum use in U.S and contributes to 35 % of greenhouse gas emissions
• Light-duty vehicle fleet, largely dominated by gasoline engines, accounts for 41% of petroleum use in U.S.
Total petroleum consumption by sector Energy consumption by fuel type
10% fuel economy benefit can potentially save 13 billion gal/year of gasoline
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Stringent regulations and costly emissions control approaches limit lean-gasoline vehicle availability
• Lean-gasoline engines are significantly more efficient– 5-15% efficiency gains reduce petroleum
consumption and greenhouse gases
• Lean NOx control limits their introduction – Standards getting more stringent and now
linked to HC (NMOG) emissions– Urea injectors and tanks viewed as cost-
prohibitive for light duty gasoline
• Research goals – Demonstrate technical path to emission
compliance for lean gasoline vehicles in the U.S. market• US-EPA Tier 3 compliance required
– Investigate strategies for cost-effective compliance 0
0.1
0.2
0.3
0.4
0.5
NMOG+NOx PM x 10 CO /10
Emis
sion
s le
vels
(g/m
ile)
Required Emissions Reductions
2016 2025
80% 70%
77%
Lean
-bur
n fu
el e
cono
my
impr
ovem
ent
(rela
tive
to s
toic
hiom
etric
)
U.S. transient drive cycles
BMW 120i lean gasoline vehicle on chassis dynamometer at ORNL
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Passive SCR is non-urea approach to lean gasoline NOx control
λ
NOXppm
NH3ppm
0.51.5
2.5
0
1000
2000
0
1000
2000
50 100 150 200 250
TWC Out
time, s
0.51.5
2.5
0
1000
2000
0
1000
2000
50 100 150 200 250
SCR Out
time, s
0.51.5
2.5
0
1000
2000
Engine Out
time, s
0
1000
2000
50 100 150 200 250
SCR
TWC
Passive SCR is a potential low cost strategy for reducing lean gasoline NOx emissions• Makes use of TWC
already onboard to generate NH3
• Eliminates urea tank, injector, refills
• Potentially reduces PGM relative to TWC+LNT
Ammonia (NH3) generated from NOx over TWC and stored on SCR during rich phase (λ = 0.96 – 0.99)
NOx reduced by NH3 stored on SCR during lean operation (λ = 1.4 – 2.2)
𝜆 =𝐴𝐹𝑅
𝐴𝐹𝑅&'()*+
AFR = air/fuel ratioλ <1: excess fuel λ =1: stoichiometricλ >1: excess air
SAE2010-01-0366, SAE2011-01-0306, SAE2011-01-0307
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0.00
0.05
0.10
0.15
0.20
0.25
Prior results: U.S. Tier 3 NOx+NMOG emission levels demonstrated with 5.9% gain in fuel economy
NOx
CO/10
NMHC
NH3
NOx+
NMHC
------ Tier 3 bin 30: 0.03 g/mi of NOx+HC, 1.0 g/mi of CO
-------------- -------
emiss
ions
(g/m
ile)
SCR
TWC
Pd-TWC Cu SCR
-------
• NOx is essentially eliminated
• CO slip is high (2x the limit)– clean-up catalyst and/or secondary
air injection
• THC slip presented last year was low but close to NOx+NMOG limit– Further analysis showed that
methane is ~50% of THC slip
• NH3 slip is high, indicating improved fuel efficiency possible– Improved control strategy, additional
catalyst technologies
Note: NMHC ~ NMOG for gasoline fuel
2018 CLEERS Workshop; Emiss. Control Sci. Technol. (2019) 5: 253
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= NOX & O2 sensor
= heated filter
= radio frequency sensor
Modified passive SCR system architecture for improved fuel savings while meeting Tier 3 NOx + HC and CO
sample ID Description Pt (g/l) Pd (g/l) Rh (g/l) OSC NSC Vol (l)Pd-TWC Front half of TWC 0 7.3 0 N N 0.62NS-TWC Pt + Pd + Rh 2.47 4.17 0.05 Y Y 0.82
GPF Uncatalyzed GPF - - - - - 2.47Cu-SCR Umicore small pore - - - - - 2.47
CUC Pd + OSC high 0 6.50 0 H N 1.00
Analytical Tools
T7
UEGO
T1-4
T6
T5 & P
bmwheaven.com
T8
T9 T10
T11T12
T13
T14T15RF
RF
Clean-up catalyst with high OSC
SCR: Lean NOX reduction
Heat sink, PM control
NH3 generation + TWC functionality
Lean NOX storage & NH3 generation + TWC functionality
OSC=Oxygen Storage Component; NSC=NOx storage component
Analytical Tools
Pd-only +
NSC/OSC CatalystNH3 generation, lean NOx storage + TWC
functionality
Uncatalyzed GPF
Heat sink + important for future regulation
Clean-up Catalyst
High OSC containing catalyst to convert CO
and HC during rich, and help with NH3 slip
Catalysts aged to full useful life (SCR mildly aged on engine)Fuel contained 8 ppm of sulfur8.3 g/liter-engine total PGMSome catalyst functions can be combined into one brick
TWC
NSC
GPF
SCR
CUC
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BMW 2.0-liter lean direct injection engine specifications
Lean Gasoline Engine Research Platform at ORNL
• BMW N43B20 4-cylinder engine came from MY2008 BMW 120i (E87) vehicle and was sold from 2007-2011
• 2.0-liter naturally aspirated direct injection gasoline engine with a rated power of 125 kW at 6700 rpm and torque of 210 Nm at 4250 rpm
• Engine controller developed by National Instruments mimics OEM combustion strategies
Engine Model Number N43B20Displaced volume 1995 cm3
Number of cylinders 4Number of valves 4 per cylinderStroke 90 mm Bore 84 mm Compression ratio 12.0:1Rated Power 125 kW at 6700 rpmRated Torque 210 Nm at 4250 rpm
BMW 120i lean gasoline vehicle on chassis dynamometer at ORNL
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• Two injections: one during intake stroke and one late in compression stroke close to TDC
• Multiple spark events• λ ranges 1.4 – 1.6• Limited to 4500 rpm and 55-75% load
0
200
400
600
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Inje
ctor
Driv
e Vo
ltage
(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% Loadl=1.9
1500 rpm, 65% Loadl=1.38
1500 rpm, 31% Loadl=1.0
Center mounted combustion system design with three main combustion modes
Lean Stratified
• Fuel injections close to TDC• Multiple spark events• λ ranges 1.6 – 2.2• Limited to 4500 rpm and 55% load
Lean Homogeneous
Stoichiometric
• Two injections: one during intake stroke and a smaller one early in compression stroke
• Single spark event• λ = 1.0• Entire engine operating range
2000 3000 4000 5000 6000 7000
200180160140120100
80604020
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
Engine Speed (rpm)
Engi
ne T
orqu
e (N
-m)
Lean Stratified
Lean Homogeneous
Stoichiometric
λ
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To simulate drive cycle, GM provided 6-mode pseudo-transient cycle utilized for passive SCR evaluation
engi
ne s
peed
, rpm
engi
ne lo
ad, b
ar
0
5
10
15
20
25
30
0
500
1000
1500
2000
2500
3000
3500
0 200 400 600 800 1000 1200 1400time, s
Operating pseudo-transient cycle closely captures fuel consumption benefit relative to stoichiometric operation observed in vehicle study*• 9.6% with pseudo-transient drive cycle• 10% with FTP vehicle study
* - SAE2010-01-2267, SAE2011-01-1218
Speed[rpm]
Load[bar]
Default Mode
1000 1.0 LS
1500 2.0 LS
1500 4.0 LS
2000 3.0 LS
2000 5.0 LH
3000 8.0 StoichLS=lean stratified, LH=lean homogeneous
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To simulate drive cycle, GM provided 6-mode pseudo-transient cycle utilized for passive SCR evaluation
engi
ne s
peed
, rpm
time, s
* - SAE2010-01-2267, SAE2011-01-1218
Speed[rpm]
Load[bar]
Default Mode
1000 1.0 LS
1500 2.0 LS
1500 4.0 LS
2000 3.0 LS
2000 5.0 LH
3000 8.0 StoichLS=lean stratified, LH=lean homogeneous
0
500
1000
1500
2000
2500
3000
3500
0 200 400 600 800 1000 1200 1400
91 % lean operation
lean slean hstoich
Operating pseudo-transient cycle closely captures fuel consumption benefit relative to stoichiometric operation observed in vehicle study*• 9.6% with pseudo-transient drive cycle• 10% with FTP vehicle study
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Engine out
• NOx is essentially eliminated at SCR• NH3 slip still observed, with some NH3 converted back to NOx over CUC catalyst
Investigate operating strategies for improved fuel efficiency while meeting Tier 3 emission standards
0500
1000150020002500
0500
1000150020002500
200400600800
0 700 1400 0 700 1400 0 700 1400 0 700 1400 0 700 1400
TWC out NSC out SCR out CUC out
NO
x, p
pmN
H 3, p
pmT,
ºC
time, s
GPF SCR CUC
TWC
NSC
Pd-TWC NS-TWC Cu-SCR Clean-UpCatalyst
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Rich NOx is ~3x lean NOx, potential for ~3x NH3
0
100
200
300
400
500
mm
ol
rich NOxlean NOx
Some rich NOx is converted to NH3by TWC
0
100
200
300
400
500 rich NH3lean NOx
,-.,/0 =1.171)*+ ,/0
2345 ,/0 =2.92
Some lean NOx is stored, additional NH3 made from stored NOx by NSC
0
100
200
300
400
500
,-.,/0 =1.88
rich NH3lean NOx
0
100
200
300
400
500 NH3NOx
0
100
200
300
400
500 NH3NOx
NOx eliminated, NH3 slip observed
NH3 slip reduced, with some NH3converted to NOx
Engine out TWC out NSC out SCR out CUC out
5-function emission control system enables efficient NH3 generation and utilization for lean NOx control
GPF SCR CUC
TWC
NSC
Pd-TWC NS-TWC Cu-SCR Clean-UpCatalyst
NOx and NH3 inventory
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0 700 1400
• High CO slip during rich operation• THC slip is low during both lean and rich operation, slightly increases during prolonged lean operation
CO
, %TH
C, p
pmT,
ºC
time, s
0.0
1.0
2.0
3.0
0
3000
6000
9000
Engine out TWC out NSC out SCR out CUC out
200400600800
0 700 1400 0 700 1400 0 700 1400 0 700 1400
GPF SCR CUC
TWC
NSC
Pd-TWC NS-TWC Cu-SCR Clean-UpCatalyst
Investigate operating strategies for improved fuel efficiency while meeting Tier 3 emission standards
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• TWC+NSC combination enables more efficient NH3 generation and provides pathway for increasing fuel economy benefit
• 0.03 g/mile NOx+NMOG tailpipe emissions demonstrated with FUL equivalent performance
• CUC decreases CO and HC emissions and helps with NH3 slip, but some NH3 converted to NOx
• Further CO reduction is needed and promising solutions are currently under investigation
0.00
0.05
0.10
0.15
0.20
0.25
Up to 8.3% fuel efficiency improvement achieved with improved system architecture
NOx NMHC NOx+
NMHC
NH3
------------
------ Tier 3 bin 30: 0.03 g/mi of NOx+NMOG,1.0 g/mi of CO
SCR
TWC
GPF SCR CUC
TWC
NSC
g/m
ile
------------ ------------0
2
3
5
6
8
9
PGMg/liter-engine
0
2
4
6
8
10 ------------max
Fuel economy improvement
relative to stoich
%
GPF SCR CUC
TWC
NSC
CO/10
------------
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Summary
• Modified 5-function passive SCR system architecture evaluated for improved fuels savings and meeting Tier 3 emissions regulations
• 8.3% fuel economy benefit achieved compared to 5.9% improvement with a TWC+SCR system, while meeting Tier 3 NOx+HC (0.03 g/mi)
• Combination of Pd-only and NS-TWC enable efficient NH3 generation and improved fuel efficiency
• CUC catalyst decreases CO and HC emissions and helps with NH3 slip, some of the NH3 is converted back to NOx
• More research is needed to further control CO emissions, improve NH3 utilization and increase fuel economy
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ORNL procured MAHLE TJI engine for lean gasoline emission control research
• MAHLE TJI engine procured as a new lean gasoline engine platform– based on a 2.3L Ford EcoBoost engine platform– provides relevant turbo-boosted stoichiometric baseline
for comparison– offers wider range of ultra lean operation– capable of better control over exhaust composition and
temperatures
MAHLETurbulentJet Ignition
Images from MAHLE
MAHLE TJI will be used to generate a wide range of exhaust conditions that will allow us to fully investigate the emission control system functionality
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THANK YOUVitaly Prikhodko
Oak Ridge National LaboratoryNational Transportation Research Center
https://www.ornl.gov/ntrc