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Simulation of Exhaust Gas Aftertreatment Systems -Reaction Engineering in Automotive Applications
Dr. Daniel Chatterjee
Memorial Colloquium Prof. Dr. Dr. h.c. Jürgen Warnatz
31.05.2008
Dr. D. Chatterjee, GR/VPE 2
Outline
� Emission Legislations
� Exhaust Gas Aftertreatment Systems
� Simulation of Exhaust Gas Aftertreatment Systems
� Modeling of SCR-Systems
� Summary
Dr. D. Chatterjee, GR/VPE 3
European Emission Legislation
Since the introduction of the emission legislation the standards were reduced drastically
Test procedure: ESCEU 5 not yet defined by law
limits in discussion
Emission legislation for CO, HC, NOx and PM is the driving force for exhaust gas aftertreatment
NOx (g/kWh)
CO
(g
/kW
h)
PM (g/kWh)
5,0
2,1
3,51,5 0,02
2,0
EU 3
EU 4EU 5
0,36
0,15
0,14,0
4,5
8,07,0
EU 2
EU 1
HC+NOx (g/km)
CO
(g
/km
)
PM
(g/km)
0,560,50,3
0,025
0,005
0,23
EU 3
EU 4
0,14
0,08
0,05
0,641,0
2,72
0,970,7
EU 2
EU 1
EU 5
Commercial
Vehicles
Passenger
Cars
3
Dr. D. Chatterjee, GR/VPE 4
Development of Emission Limits of Diesel Passenger Cars
Improvement of the engine/combustion process is needed. In addition highly efficient
active aftertreatment systems are required to meet emission limits.
2009-112014-15
USA USA
56% NOx control
Dr. D. Chatterjee, GR/VPE 5
Emission Certification Testcycles:New European Driving Cycle (NEDC)
Exhaust System are operated under highly transient operation conditions regarding: mexh., Texh., CO, HC, NOx, PM,…
Dr. D. Chatterjee, GR/VPE 6
Outline
� Emission Legislations
� Exhaust Gas Aftertreatment Systems
� Simulation of Exhaust Gas Aftertreatment Systems
� Modeling of SCR-Systems
� Summary
Dr. D. Chatterjee, GR/VPE 7
SCR-Based Exhaust Gas AftertreatmentTechnology: BlueTEC II - GL 320 CDI
Dosing
Valve
BlueTEC II
DPF
Oxi-Catalyst
SCR-
Catalyst
• The exhaust system BlueTEC II is based on the NH3 based SCR process
used already for power plant DeNOx.
• BlueTEC II was introduced for Heavy Duty Trucks with EURO IV and EURO V.
AdBlue/Urea
TankOxidation of CO, HC, NO
Soot Trapping
NOx Reduction
With NH3Urea Injection
Dr. D. Chatterjee, GR/VPE 8
NSC Based Exhaust Gas AftertreatmentTechnology: BlueTEC I - E320 CDI
NSC-Catalyst
Oxi-Catalyst
SCR-
Catalyst
BlueTEC I
BlueTEC I
New exhaust gas aftertreatment system based on the combination of
NSC+SCR an low emission combustion. No urea dosing required.
DPF
Oxidation of CO, HC, NO
NOx Trapping/Reduction and
NH3 Formation Soot TrappingNOx Reduction
with NH3
Dr. D. Chatterjee, GR/VPE 9
Overview: AT-Components and Systems
AT*-Components (Heavy Duty and Passenger Cars):
AT*-Systems:
DOC+DPF
DOC+DPF+NSC
DOC+DPF+SCR
(BlueTEC II)
DOC+NSC+DPF+SCR
(BlueTEC I)
AdBlue-Injection
Three-Way Catalyst Oxidation Catalyst Diesel Particle Filter NOx Storage Catalyst SCR Catalyst
DOC SCRNSCDPFTWC
TWC only
Diesel Engines
*AT = Aftertreatment
Simulation assisted development required to manage complexity
regarding costs an time.
Dr. D. Chatterjee, GR/VPE 10
Outline
� Emission Legislations
� Exhaust Gas Aftertreatment Systems
� Simulation of Exhaust Gas Aftertreatment Systems
� Modeling of SCR-Systems
� Summary
Dr. D. Chatterjee, GR/VPE 11
Exhaust Aftertreatment ModelingExACT:
1D- Simulation of combined
Exhaust Aftertreatment Systems
3D-Simulation:Optimization of Geometry
for Individual Components
Applications:
•Effect of non uniform
inlet conditions
•Temperature/Soot
distribution
•Light-off optimization
Applications:
•Testcycle performance
•System-design
•Operating strategies
0.5s
24s
Focus: SCR-, NSC-, DPF-,
DOC-, TWC-SystemsFocus: Urea Injection, DPF
Dr. D. Chatterjee, GR/VPE 12
ExACT Exhaust Aftertreatment System Modeling:Application Examples
0
50
100
150
200
250
300
350
400
450
500
0 200 400 600 800 1000 1200
time [s]
Te
mp
era
ture
[°C
]
T after NSK
T after NSK calc
Tout NSC, exp,
Tout NSC, sim.
Temperatures
Rußbeladung & Differenzdruck
0
5
10
15
20
25
30
35
40
45
50
0 300 600 900 1200
Zeit [s]D
iffe
ren
zd
ruc
k [
mb
ar]
Ru
ßb
ela
du
ng
[g
]
backpressure - measured
backpressure - computed
soot mass in filter - computed
Soot Loading/Pressure LossECU-Development
„Virtual Testbench“
Electronic Control Unit (ECU) ModelElectronic Control Unit (ECU) Model
Hardware implementation of
ECU model
Software in the Loop (SiL):
Test of ECU model on engine test bench
Prediction of Soot, NOx, CO, HC Conversion
0 200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Cu
mu
lati
ve
NO
x [
g]/
cy
cle
time [s]
inlet AGN system
outlet T original
outlet T+20°C (whole cycle)
outlet T+40°C (whole cycle)
outlet T+20°C (first 600s)
outlet T+40°C (first 600s)
Euro 5
Euro 6
0 200 400 600 800 1000 1200
0.5
1
1.5
2
2.5
3
3.5
4
Cu
mu
lati
ve
NO
x [
g]/
cy
cle
time [s]
inlet AGN system
outlet T original
outlet T+20°C (whole cycle)
outlet T+40°C (whole cycle)
0 200 400 600 800 1000 12000
50
100
150
200
250
300
time [sec]
NO
x [
pp
m]
NOx inlet EGA-system
NOx outlet EGA-system
Dr. D. Chatterjee, GR/VPE 13
Simulation of Exhaust Gas AftertreatmentSystems
Requirements on Simulation Models:
� Scalability:
(e.g. catalyst volume can range from 0.5 L (e.g. PC DOC) to 34L (e.g. HD SCR))
� Valid for a wide range of operating conditions
(e.g. exhaust temperatures from 100°C to 800°C)
� Extrapolation capability
(Not all inlet conditions combinations can be tested/measured.)
Physical and chemical based model approach required
Dr. D. Chatterjee, GR/VPE 14
surface reactions:
(chemistry)
z [m]
r[m
]
0 0.025 0.05 0.075 0.10
0.025
0.05
0.075
0.1
monolith:
(solid temperature)
Modeling of all relevant processes required for predictive simulations.
Variation of
coating/ amount
of precious metals.
requires recalibration
Variation of
coating/ amount
of precious metals.
requires recalibration
single channel:
(heat and
mass transfer) Variation of geom.
parameters (e. g. cell
density, length,
structure,...) possible.
Variation of geom.
parameters (e. g. cell
density, length,
structure,...) possible.
Detailed Modeling of Catalytic Converters/DPFs
Dr. D. Chatterjee, GR/VPE 15
Outline
� Emission Legislations
� Exhaust Gas Aftertreatment Systems
� Simulation of Exhaust Gas Aftertreatment Systems
� Modeling of SCR-Systems
� Summary
Dr. D. Chatterjee, GR/VPE 16
Exhaust Aftertreatment System Modeling: Example Heavy Duty SCR-System
ECU
SCR Catalyst
N2,
H2O
Urea Injection
NO
NH3
NO
NOx is reduced within the SCR catalyst by stored NH3.
Dr. D. Chatterjee, GR/VPE 17
0
100
200
300
400
500
600
0 200 400 600
time [s]
NO
x [
ppm
]
0
10
20
30
40
50
60
70N
H3 [p
pm
]
NOx
NH3
Modeling SCR-Catalytic Converters:
Texh. = 200°C, mexh. = 582 kg/h, α = 0.87, catalyst 25L, 300cpsi
Test Bench Measurement:
Concentrations Behind Catalyst
Buildup of stored NH3
η10ppm
Start of Urea
Injection
Dr. D. Chatterjee, GR/VPE 18
Modeling SCR-Catalytic Converters
Chemical Reactions: NO+NH3+
NH3 adsorption: NH3 → NH3*
NH3 desorption: NH3* → NH3
NH3 oxidation: 4NH3*+3O2 → 2N2+6H2O
NO-SCR reaction: 4NH3*+4NO+O2→4N2+6H2O
)1(3 ϑ−=NHadsads
Ckr
ϑγϑ)]1(exp[ −−=°
°
RT
Ekr
des
desdes
β
ϑ
ϑ
ϑ
−+
−= °
02.0
11
)exp( 2O
LH
NONO
NONO
P
K
C
RT
Ekr
•No NH3 adsorption/desorption equilibrium is assumed.
•Eley-Rideal kinetics for NO-SCR reaction.
•Higher O2 concentration increases SCR reaction and NH3 oxidation rates.
+SAE 2005-01-0965
NH3
NH3
NH3NH3
ϑ
β
−= °
02.0)exp( 2Oox
oxox
P
RT
Ekr
β
ϑ
−= °
02.0)exp( 2
3
O
NHNO
NO
NONO
PC
RT
Ekr
NH3
NH3
Dr. D. Chatterjee, GR/VPE 19
Modeling SCR-Catalytic Converters:Influence of NH3 Inhibition on NOx Reduction
NH3
NH3**NH3*
NOx
2000 3000 4000 5000 6000
0
200
400
600
800
1000
tempo [s]
Co
ncen
trazio
ni [p
pm
]
2000 3000 4000 5000 6000
0
200
400
600
800
1000
tempo [s]
Exp NH3
Exp N2
Exp NO
Fit NH3
Fit N2
Fit NO
EleyEleyEleyEley――――RidealRidealRidealRideal kinetics Langmuir―Hinshelwood Langmuir―Hinshelwood Langmuir―Hinshelwood Langmuir―Hinshelwood kinetics
time [s] time [s]
NH3 shut off NH3 shut off
NH3
NH3*
NOx
Powder Microreactor: GHSV = 90000 h-1, O2=2%, H2O = 1 %, NO = NH3 = 1000 ppm, T = 200 °C
NO
NH3
N2
NO
NH3
N2
0
20
40
60
80
100
120
140
160
180
200
0 500 1000 1500
time [s]
NO
x [
pp
m]
NOx, exp
NOx, sim
0
20
40
60
80
100
120
140
160
180
200
0 500 1000 1500
time [s]N
Ox [
pp
m]
NOx, exp
NOx, sim
Engine test bench: Texh.=297°C, mexh.1061 kg/h, SCR Vol.=32L, α=1.01
Dr. D. Chatterjee, GR/VPE 20
Modeling SCR-Catalytic Converters
Chemical Reactions: NO+NH3+
NH3 adsorption: NH3 → NH3*
NH3 desorption: NH3* → NH3
NH3 oxidation: 4NH3*+3O2 → 2N2+6H2O
NO-SCR reaction: 4NH3*+4NO+O2→4N2+6H2O
)1(3 ϑ−=NHadsads
Ckr
ϑγϑ)]1(exp[ −−=°
°
RT
Ekr
des
desdes
β
ϑ
ϑ
ϑ
−+
−= °
02.0
11
)exp( 2O
LH
NONO
NONO
P
K
C
RT
Ekr
•No NH3 adsorption/desorption equilibrium is assumed.
•Two-sites L.-H. expression accounts for NH3 inhibition of the SCR reaction.
•Higher O2 concentration increases SCR reaction and NH3 oxidation rates.
+SAE 2005-01-0965
NH3
NH3
NH3NH3
ϑ
β
−= °
02.0)exp( 2Oox
oxox
P
RT
Ekr
Dr. D. Chatterjee, GR/VPE 21
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 100 200 300 400 500
time [s]N
H3
, in
[-]
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
0.018
0.020
NH
3,
ou
t [-
]
SCR-Model Validation: Testcycle Simulation (ETC)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 100 200 300 400 500
time [s]
NO
x [-
]
NOx in
NOx out, exp.
NOx out, sim.
NH3 in
NH3 out, exp.
NH3 out, sim.
The overall NOx efficiency within an testcycle
is predicted with an typical accuracy of 3-4%
OM906, SCR : Argillon9999 18L, 300cpsi
Dr. D. Chatterjee, GR/VPE 22
SCR-Model Application: Identification of RequiredCatalyst Volume - Steady State NOx Conversion
η10ppm, α = optimized ηmax, α = 1
Catalyst: 18L, 300cpsi
ESC
operating points
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
• Low Texh. : NOx conversion limited by slow SCR kinetics.
kinetic limitation
• High mexh.: NOx conversion limited by diffusion effects � high NH3 slip.
diffusion effects
• High Texh. : NOx conversion limited by low NH3 storage capacity and NH3 oxidation.
low NH3 storage,
NH3 oxidation
Dr. D. Chatterjee, GR/VPE 23
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
η10ppm η10ppm
η10ppm
14L 18L
25L
908825
898118
816114
ηETC [%]ηESC [%]catalyst
volume [L]
*10% deduction on the NOx conversion if α > 1
18L catalyst volume is sufficient to fulfill the
application target of 80% NOx conversion.
SCR-Model Application: Identification of RequiredCatalyst Volume - Steady State NOx Conversion
OM906LA, α=optimized, SCR : Argillon9999, 300cpsi
Dr. D. Chatterjee, GR/VPE 24
SCR Model Application:Transient behavior within an ETC tescycle
α=1, Catalyst: 18L, 300cpsi
NOx in/out NH3 in/out
Ts along monolith axis Stored NH3* along monolith axis Stored NH3* within monolith wall
Dr. D. Chatterjee, GR/VPE 25
Exhaust Aftertreatment System Modeling of Advanced SCR Systems: DOC+DPF+SCR
ECU
SCR Catalyst
N2,
H2O
Urea Injection
NO
NH3
NO
DOC DPF
,NO2
DOC upstream of the SCR oxidizes NO to NO2, which improves SCR performance.
Dr. D. Chatterjee, GR/VPE 26
Modeling SCR-Catalytic Converters:
Chemical Reactions: NO+NO2+NH3
� NO2 disporoportion: 2NO2 +H2O ⇔ HNO2 + HNO3
� HNO2 reaction with NH3: HNO2 + NH3* → N2 + 2H2O
� NH4NO3 adsorption-desorption: NH3*+ HNO3 ⇔ NH4NO3*
� HNO3 reaction with NO: HNO3 + NO ⇔ HNO2 + NO2
� N2O formation: NH3*+ HNO3 → N2O + 2H2O
� NO2- SCR reaction: 4NH3*+ 3NO2→ 3.5N2 + 6H2O
•HNOx and NH4NOx are considered as intermediate species in the mechanism.
•No equilibrium is assumed for disproportion, adsorption/desoprtion etc.
•Two-sites L.-H. expression accounts for NH3 inhibition of the HNO3+NO reaction.
Fast SCR:
2NH3+NO2+NO
→ 2N2+3H2O
(NH4NO2)
(NH4NO3*)
� Fast-SCR reaction: 2NH3*+ NO2 + NO→ 2N2 + 3H2O
• The global reaction between NH3+NO+NO2 is very fast.
• However, the direct reaction between NH3 and NO2 is slow.
Dr. D. Chatterjee, GR/VPE 27
Low temperature� 2NH3 + 2NO2 � N2 + H2O + NH4NO3 (ammonium nitrate formation)
High Temperature
� NH4NO3 � N2O + 2H2O (ammonium nitrate decomposition)
� 6NO2 + 8NH3 � 7N2 + 12H2O (NO2 SCR)
150 175 200 225 250 275 300 325 350 375 400 425 450
0
100
200
300
400
500
600
700
800
900
1000
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
Co
ncn
etr
atio
n (
pp
m)
Temperature (°C)
N2ONO
2
NO
NH3 N
ba
lan
ce
(pp
m)N
2
N balance
Modeling SCR-Catalytic Converters:NO2+NH3 Experiment
Dr. D. Chatterjee, GR/VPE 28
Modeling SCR-Catalytic Converters:Proposed Reaction Mechanism for NO2+NO+NH3on V-Based and Fe-Zeolites SCR Catalysts:
Data analysis and literature supports the assumption of a similar reaction
mechanism on V-based and Fe-Zeolites SCR catalysts.
C. Ciardelli, I. Nova, E. Tronconi, D. Chatterjee, B. Bandl-Konrad, Chem. Commun. 23 (2004), 2718,
D. Chatterjee, T. Burkhardt, M. Weibel, E. Tronconi, I. Nova, C. Ciradelli, SAE 2006-01-0468,
I. Nova, C. Ciardelli, E. Tronconi, D. Chatterjee, B. Bandl-Konrad, Catal. Today, 114 (2006), 3,
A.Gossale, I. Nova, E. Tronconi, D. Chatterjee, M. Weibel, J. of Catalysis (submitted)
O. Kröcher, 1st Conference MinNOx, Feb. 2007 Berlin (Germany).
2NO2
↔↔↔↔ N2O
4+ H
2O ↔↔↔↔ HONO + HNO
3
NH3ads
[NH4NO
2] →→→→ N
2+ 2H
2O
NH4NO
3
NH3ads
2NO2 + 2NH3 →→→→ NH4NO3 + N2 + H2O2NO2
↔↔↔↔ N2O
4+ H
2O ↔↔↔↔ HONO + HNO
3
NH3ads
[NH4NO
2] →→→→ N
2+ 2H
2O
NH4NO
3
NH3ads
2NO2 + 2NH3 →→→→ NH4NO3 + N2 + H2O2NO2 + 2NH3 →→→→ NH4NO3 + N2 + H2O
NO
HONO + NO2 NH4NO3 + NO →→→→ N
2+ NO
2+ 2H
2ONH4NO3 + NO →→→→ N
2+ NO
2+ 2H
2O
2 NH3 + NO2 + NO →→→→ 2 N2 + 3 H2O
[NH4NO
2] →→→→ N
2+ 2H
2O
NH3ads
NO-NO2/NH
3
NO2/NH
3
NH4NO
3↔↔↔↔ NH
3+ HNO
3NH
4NO
3↔↔↔↔ NH
3+ HNO
3NH
4NO
3↔↔↔↔ NH
3+ HNO
3
Dr. D. Chatterjee, GR/VPE 29
Modeling SCR-Catalytic Converters:
Chemical Reactions: NO+NO2+NH3
� NO2 disporoportion: 2NO2 +H2O ⇔ HNO2 + HNO3
� HNO2 reaction with NH3: HNO2 + NH3* → N2 + 2H2O
� NH4NO3 adsorption-desorption: NH3*+ HNO3 ⇔ NH4NO3*
� HNO3 reaction with NO: HNO3 + NO ⇔ HNO2 + NO2
� N2O formation: NH3*+ HNO3 → N2O + 2H2O
� NO2- SCR reaction: 4NH3*+ 3NO2→ 3.5N2 + 6H2O
•HNOx and NH4NOx are considered as intermediate species in the mechanism.
•No equilibrium is assumed for disproportion, adsorption/desoprtion etc.
•Two-sites L.-H. expression accounts for NH3 inhibition of the HNO3+NO reaction.
Fast SCR:
2NH3+NO2+NO
→ 2N2+3H2O
(NH4NO2)
(NH4NO3*)
• The global reaction between NH3+NO+NO2 is very fast.
• However, the direct reaction between NH3 and NO2 is slow.
Dr. D. Chatterjee, GR/VPE 30
SCR-Modeling: Influence of NO2 on SCR Conversion Efficency
Steady state NOx conversionSteady state outlet concentrations
Good prediction quality of NO2 influence on product selectivity and NOx conversion.
0.0 0.2 0.4 0.6 0.8 1.0
0
200
400
600
800
1000 experimental
calculated
N2O
NO
NO2
NH3
N2
ppm
NO2/NO
x feed ratio
0.0 0.2 0.4 0.6 0.8 1.00
20
40
60
80
100
experimental
calculated
275°C
225°C
200°C
NO2/NO
x feed ratio
NO
x c
onve
rsio
n (
%)
1000
800
600
400
200
0
concentration [ppm]
100
80
60
40
20
0
NOxconversion [%]
0.0 0.2 0.4 0.6 0.8 1.0
NO2/NOx feed ratio
0.0 0.2 0.4 0.6 0.8 1.0
NO2/NOx feed ratioMicroreactor sim./exp.:
Feed 1000ppm NH3, 1000ppm NOx, GHSV = 210000 h-1 at 225°C
Microreactor sim./exp.:
Feed 1000ppm NH3, 1000ppm NOx, GHSV = 210000 h-1
Dr. D. Chatterjee, GR/VPE 31
1D-Exhaust Aftertreatment System Modeling:DOC+SCR Simulation (ESC)
• Model predicts transient temperatures and species conversions within testcycle
• Presence of NO2 in the SCR inlet exhaust increases NOx conversion in
the lower temperature parts of the ESC.
NO2/NOx=DOCout at SCR inletNO2/NOx=50% at SCR inlet
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 500 1000 1500
time [s]
NO
x [-
]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 500 1000 1500
time [s]
NO
x [-
]
(NO2/NOx)in≈ 40%-50%
NO2/NOx behind DOC
0
10
20
30
40
50
60
70
80
90
100
0 500 1000 1500
time [s]
NO
2/N
Ox
[%]
100
150
200
250
300
350
400
450
tem
pe
ratu
re [
°C]
OM906, α=1, DOC: JM DF87 (20g/ft3), SCR : Argillon9999 18L, 300cpsi
Baseline 0% NO2
NOx inlet
Baseline 0% NO2
NO2/NOx=DOCout
Dr. D. Chatterjee, GR/VPE 32
DOC aged
30
40
50
60
70
NO
x-c
on
v.
[%]
0 % NO2
50 % NO2
20g/ft3
40g/ft3
55g/ft3
DOC aged
30
40
50
60
70
NO
x-c
on
v.
[%]
0 % NO2
50 % NO2
20g/ft3
40g/ft3
55g/ft3
DOC aged
30
40
50
60
70
NO
x-c
on
v.
[%]
0 % NO2
50 % NO2
20g/ft3
40g/ft3
55g/ft3
20g/ft3
40g/ft3
55g/ft3
DOC degreened
30
40
50
60
70
NO
x-c
on
v.
[%]
20g/ft3
40g/ft3
55g/ft30 % NO2
50 % NO2
DOC degreened
30
40
50
60
70
NO
x-c
on
v.
[%]
20g/ft3
40g/ft3
55g/ft30 % NO2
50 % NO2
DOC degreened
30
40
50
60
70
NO
x-c
on
v.
[%]
20g/ft3
40g/ft3
55g/ft3
20g/ft3
40g/ft3
55g/ft30 % NO2
50 % NO2
Exhaust Aftertreatment System Modeling:DOC Optimization (Cold Start FTP)
0 0.5 1 1.5 2 0 0.5 1 1.5 2
relative DOC volume relative DOC volume
• Noble metal loading higher than 40 g/ft3 required
• Significant volume reduction possible if degreened state could be stabilized.
Dr. D. Chatterjee, GR/VPE 33
Outline
� Emission Legislations
� Exhaust Gas Aftertreatment Systems
� Simulation of Exhaust Gas Aftertreatment Systems
� Modeling of SCR-Systems
� Summary
Dr. D. Chatterjee, GR/VPE 34
Simulation of Complex Exhaust Gas Aftertreatment Systems: Summary
• Exhaust aftertreatment simulation is needed due to increasing system
complexity and required system performance.
• Exhaust aftertreatment simulation has become a very efficient tool for
system design and operation strategies.
• Usage of global chemistry offers fast calculation times. However, a detailed
understanding of the chemical processes is required.
• Refined (reaction kinetic) models needed to improve prediction quality
and to reduce recalibration effort.
• Ongoing development needed for new types of catalyst, e.g. NH3-Slip
Catalyst.
• Aging and noble metal variations have to be included in future models.