ORNL is managed by UT-Battelle, LLC for the US Department of Energy

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

2

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

3

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

4

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

5

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

6

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

7

= 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

8

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

9

• 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

10

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

11

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

12

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

13

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

14

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

17

• 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

------------

18

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

prikhodkovy@ornl.gov

Oak Ridge National LaboratoryNational Transportation Research Center

https://www.ornl.gov/ntrc