Parametric Study of NOx Adsorber Regeneration in Transient ......Mercedes 1.7 L CIDI Engine Lightoff...
Transcript of Parametric Study of NOx Adsorber Regeneration in Transient ......Mercedes 1.7 L CIDI Engine Lightoff...
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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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
Adsorber A Performance, Hot-Start LA-4 Cycle
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
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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
Adsorber A Performance, Hot-Start LA-4 Cycle
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Adsorber A yields lowest NOx emissions
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0.4
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0.8
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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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Adsorber A yielded the highest cycle-average NOx reduction. Longer duration regenerations
generally improved performance
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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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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.
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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
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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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
Minimum AFR During Regeneration
CO
Em
issi
on
s (g
/mi)
Adsorber A Adsorber B Adsorber C Adsorber E
Tier 2 Bin 5 Limit 4.2 g/mi
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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0.12
0.14
10.2 11.2 11.6
Minimum AFR During Regeneration
NM
HC
Em
issi
on
s (g
/mi)
Ads A Ads B
Ads D Ads E
Tier 2 Bin 8 Limit 0.125 g/mi
Tier 2 Bin 5 Limit 0.090 g/mi
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
10.2 11.2 11.6
Minimum AFR During Regeneration
NM
HC
Em
issi
on
s (g
/mi)
Adsorber A Adsorber B
Adsorber C Adsorber E
Tier 2 Bin 8 Limit 0.125 g/mi
Tier 2 Bin 5 Limit 0.090 g/mi
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Questions?
• For further information, contact− Brian West, 865-946-1231
− Scott Sluder, [email protected]
− See SAE 2002-01-2876
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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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
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Time (s)N
A In
let
Tem
p (
C)
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Sp
eed
(M
PH
)
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Time (s)
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t T
emp
erat
ure
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)
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eed
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