Parametric Study of NOx Adsorber Regeneration in Transient ......Mercedes 1.7 L CIDI Engine Lightoff...

1

OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY

Parametric Study of NOx Adsorber Regeneration in Transient Cycles

Brian WestScott Sluder

Oak Ridge National Laboratory

Sponsor: Kathi EppingDOE FreedomCAR and Vehicle Technologies Office

8th DEER WorkshopAugust 25-29, 2002

2


Objective:

Determine effects of rich pulse air:fuel ratio and duration on NOx adsorber performance in transient operation

Motivation: Augment what can be learned from quasi-steady bench flow experiments with fixed flows and temperature

3


Experimental Approach• Utilized Mercedes A170 CDI as “gas

generator” • ECU unmodified; regeneration

controlled off-board• Used synthesis gas as a reductant

− Laboratory experiment, not intended for production

− Syngas nominally 2/3 CO, 1/3 H2, 3% C2H4

• Ran multiple hot LA-4 cycles to assess device performance on transient cycle− At least 3 replicate hot-starts at each

condition− Test sequence: richest to leanest

• Measured indicated AFR (iAFR) at adsorber inlet during regeneration events with UEGO

4


Reductant delivered upstream of lightoff catalyst for regeneration

Mercedes

1.7 L CIDI

EngineLightoffcatalyst

CDPF NOxAdsorber

ReductantDelivery

0 200 400 600 800 1000 1200 1400

Time (s)

1400

Regeneration events on LA-4• Driver’s aid controls:• Timing• Duration

• Auxiliary engine controller meters gas volume

5


MECA members provided five prototype NOx adsorbers for evaluation.

All units were 2.5 liter volume (5.66 in x 6 in round)

Unknown100300E

Yes/No164400D

Yes/No120400C

Yes/No120400B

Yes/Yes164400A

Contains Barium/Alkali metals

Precious Metalg/ft3Cells/in2Adsorber

6


Decreasing air/fuel ratio during regeneration decreases tailpipe NOX emissions

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 200 400 600 800 1000 1200 1400

Time (s)

Cum

ulat

ive

NO

x E

mitt

ed (

g)

10.2 AFR, 2 Sec11.2 AFR, 2 Sec11.6 AFR, 2 Sec11.9 AFR, 2 Sec14.2 AFR, 2 Sec

Adsorber A Performance, Hot-Start LA-4 Cycle

Tier 2 Bin 8 Limit

Tier 2 Bin 5 Limit

7


0.0

0.5

1.0

1.5

2.0

2.5

0 200 400 600 800 1000 1200 1400

Time (s)

Cu

mu

lati

ve N

Ox

Em

itte

d (

g)

11.2 AFR, 1.5 Sec 11.2 AFR, 2.0 Sec 11.2 AFR, 2.5 Sec


Tier 2, Bin 8 Limit

Tier 2, Bin 5 Limit

Shorter rich pulse duration significantly affects NOx performance of adsorber A

0.0

0.5

1.0

1.5

2.0

2.5

0 200 400 600 800 1000 1200 1400

Time (s)

Cu

mu

lati

ve N

Ox

Em

itte

d (

g)

10.2 AFR, 1.5 Sec 10.2 AFR, 2.0 Sec 10.2 AFR, 2.5 Sec


Tier 2, Bin 8 Limit

Tier 2, Bin 5 Limit

10.2 iAFR 11.2 iAFR

1.5 s

1.5 s

2.0 s

2.5 s

2.0 s

2.5 s

8


Adsorber A yields lowest NOx emissions

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 200 400 600 800 1000 1200 1400

Time (s)

NO

x E

mitt

ed (

g)

Adsorber A Adsorber B Adsorber C Adsorber E

Hot-Start LA-4 Cycle, 2 Second Rich Duration, AFR 10.2

9


Adsorber A yielded the highest cycle-average NOx reduction. Longer duration regenerations

generally improved performance

70

75

80

85

90

95

100

A B C D E

Cyc

le N

Ox

Red

uctio

n (%

)

1.5 s 2.0 s 2.5 s

Hot-Start LA-4 Cycle, 10.2 iAFRRegeneration Duration

10


Idle-capacity experiment shows that adsorber A has highest capacity at low temperature

All adsorbers show near 100% capture of NOX for a short period at less than 150 C exhaust temperature.

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200 1400

Time (s)N

Ox

Slip

(p

pm

)Adsorber A Adsorber B Adsorber C Adsorber D Adsorber E

Reg

ener

atio

n

Tu

rned

Off

AE

C

D

B

0

50

100

150

200

250

300

350

400

450

500

0 200 400 600 800 1000 1200 1400

Time (s)

NA

Inle

t T

emp

(C

)

Adsorber A Adsorber B Adsorber C Adsorber D Adsorber E

Regeneration Turned Off

11


NOx slip during regeneration is not a significant source of NOx emissions. For the LA-4, hill 2 is a

major source of NOx

0.0

0.5

1.0

1.5

2.0

A B C D E A B C D E

Cu

mu

lativ

e N

Ox

Em

itted

(g

)

Regeneration Hill 2 Other Lean Periods

2.5 s Duration - 10.2 iAFR2.0 s Duration - 10.2 iAFR

12


Added hill 2 regeneration improves adsorber D overall, but has only short term effect on adsorber B

-0.5

0.0

0.5

1.0

1.5

2.0

0 200 400 600 800 1000 1200 1400Time (s)

Cum

ulat

ive

NO

x (g

)

B with added regeneration

B 2.5 Sec, 10.2 iAFR

D 2.5 Sec, 10.2 iAFR

D with added regeneration

Regeneration flagCircled event is added regeneration

13


CO emissions were only problematic at the richest and longest duration regenerations

2.0 Second Rich Pulse 2.5 Second Rich Pulse

0.0

1.0

2.0

3.0

4.0

5.0

6.0

10.2 11.2 11.6

Minimum AFR During Regeneration

CO

Em

issi

on

s (g

/mi)

Ads A Ads B

Ads D Ads E

Tier 2 Bin 5 Limit 4.2 g/mi

0.0

1.0

2.0

3.0

4.0

5.0

6.0

10.2 11.2 11.6


CO

Em

issi

on

s (g

/mi)

Adsorber A Adsorber B Adsorber C Adsorber E


14


Adsorbers C and D are more effective at eliminating HC emissions

2.0 Second Rich Pulse 2.5 Second Rich Pulse

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

10.2 11.2 11.6


NM

HC

Em

issi

on

s (g

/mi)

Ads A Ads B

Ads D Ads E



0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

10.2 11.2 11.6


NM

HC

Em

issi

on

s (g

/mi)

Adsorber A Adsorber B

Adsorber C Adsorber E



15


Summary and Conclusions

• Adsorbers with highest apparent storage capacity yielded best NOx performance on “hill 2” and overall

• Reducing NOx slip during lean periods has more potential for improved cycle performance than slip during regeneration

• For a fixed regeneration schedule, reducing iAFR and and/or increasing duration of regeneration improves NOx performance− at expense of CO emissions

− at expense of HC emissions for 2.0 second duration

− with improved HC emissions for 2.5 second duration

16


Questions?

• For further information, contact− Brian West, 865-946-1231

[email protected]

− Scott Sluder, [email protected]

− See SAE 2002-01-2876

17


Redesigning the regeneration schedule achieved lower exhaust temperatures than previous work

DVECSE Regeneration ScheduleSAE 2000-01-2912

New Regeneration Schedule

The new regeneration schedule was used for all experiments

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000 1200 1400

Time (s)N

A In

let

Tem

p (

C)

0

20

40

60

80

100

120

140

160

180

200

Sp

eed

(M

PH

)

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000 1200 1400

Time (s)

NA

Inle

t T

emp

erat

ure

(C

)

0

20

40

60

80

100

120

140

160

180

200

Sp

eed

(M

PH

)

Date post:	05-Mar-2021
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

Parametric Study of NOx Adsorber Regeneration in Transient ......Mercedes 1.7 L CIDI Engine Lightoff...

Documents