NOX ABATEMENT - CLEERS€¦ · MODEL VS BRACK (2016) Urea Decomposition Urea mass decreases over...
Transcript of NOX ABATEMENT - CLEERS€¦ · MODEL VS BRACK (2016) Urea Decomposition Urea mass decreases over...
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NOX ABATEMENT
—1D/3D simulation of urea dosing and
selective catalytic reduction
J. C. Wurzenberger, A. Nahtigal, T. Mitterfellner, K. Pachler, S. Kutschi
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WHY SIMULATION
▪ Urea SCR is the technology to reduce NOx emissions in HD applications
▪ NOx aftertreatment needs to deal with strongly transient operating conditions
▪ Deposit formation is a key aspect in the design if DEF dosing systems
▪ 3D phenomenon influenced by geometry, flow, control Candidate for 3D CFD
▪ Transient phenomenon influenced by the course of the operating conditions Candidate for Real-time system level simulation
BACKGROUND
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DEPOSITS DEPEND ON:
1. DESIGN
2. INJECTOR
3. BOUNDARY CONDITIONS
All physical phenomena can
be covered by 3D FIRE™
in detail - but long
simulation time is required.
SOLUTION: Provide CFD-
3D FIRE™ simulation
results to Real – Time
capable 1D BOOST™.
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CONTENT
1. Model / Model Validation
i. DEF Dosing (CFD)
ii. Drive Cycle Performance (SysEng)
2. Tools and Workflows
3. Use Case
4. Summary
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SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
DEF DOSINGINJECTION OF UREA-WATER SOLUTION
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SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
▪ Spray/gas interaction▪ Multicomponent evaporation
▪ Thermolysis: (NH2)2CO NH3 + HNCO
▪ Hydrolysis: HNCO + H2O NH3 + CO2
DEF DOSINGSPRAY/GAS INTERACTION
H 0 (l)2
H 0 (g)2
H 0 (l)2
H 0 (g)2
(NH ) CO (s or l)2 2
(NH ) CO (g)2 2
NH (g) + HNCO (g)3
H 02 (NH ) CO2 2
I. II. III.
(NH ) CO (s or l)2 2
(NH ) CO (s or l)2 2
(NH ) CO (g)2 2
(NH ) CO (g)2 2
H 0 (l)2
H 0 (g)2
H 0 (l)2
H 0 (g)2
(NH ) CO (s or l)2 2
(NH ) CO (g)2 2
NH (g) + HNCO (g)3
H 02 (NH ) CO2 2
I. II. III.
(NH ) CO (s or l)2 2
(NH ) CO (s or l)2 2
(NH ) CO (g)2 2
(NH ) CO (g)2 2
H2O
(NH2)2CO NH3
HNCO
NH3
CO2
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SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
▪ Spray/gas interaction▪ Multicomponent evaporation
▪ Thermolysis: (NH2)2CO NH3 + HNCO
▪ Hydrolysis: HNCO + H2O NH3 + CO2
DEF DOSINGSPRAY/GAS INTERACTION
H2O
(NH2)2CO NH3
HNCO
NH3
CO2
VelocityNH3
Uni=0.84 =0.94
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SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
▪ Spray/gas interaction▪ Multicomponent evaporation
▪ Thermolysis: (NH2)2CO NH3 + HNCO
▪ Hydrolysis: HNCO + H2O NH3 + CO2
▪ Spray/wall interaction▪ Heat transfer between spray and wall
▪ Wallfilm formation
▪ Multicomponent film evaporation & thermolysis
DEF DOSINGSPRAY/WALL INTERACTION
H2O
(NH2)2CO NH3
HNCO
NH3
CO2
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DEF DOSINGSPRAY/WALL INTERACTION -- VALIDATION
Nahtigal et al. “SCR recent development and method”, AVL International Simulation Conference, 2017
Test bench at Graz University of Technology
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J.C. Wurzenberger | CDS | 14 September 2017 | 11Public
SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
▪ Spray/gas interaction▪ Multicomponent evaporation
▪ Thermolysis: (NH2)2CO NH3 + HNCO
▪ Hydrolysis: HNCO + H2O NH3 + CO2
▪ Spray/wall interaction▪ Heat transfer between spray and wall
▪ Wallfilm formation
▪ Multicomponent film evaporation & thermolysis
▪ Cooling of walls▪ Radial and lateral heat transfer (walls, mixers,…)
DEF DOSINGCOOLING OF WALLS
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SPRAY PREPARATION MODELS
▪ Injection of urea-water solution▪ Urea-water properties: f(T,wi,g)
▪ Nozzle modeling
▪ Spray/gas interaction▪ Multicomponent evaporation
▪ Thermolysis: (NH2)2CO NH3 + HNCO
▪ Hydrolysis: HNCO + H2O NH3 + CO2
▪ Spray/wall interaction▪ Heat transfer between spray and wall
▪ Wallfilm formation
▪ Multicomponent film evaporation & thermolysis
▪ Cooling of walls▪ Radial and lateral heat transfer (walls, mixers,…)
▪ Catalytic conversion▪ Ad- and desorption, fast, standard, slow SCR,…
DEF DOSINGCATALYTIC CONVERSION
H2O
(NH2)2CO NH3
HNCO
NH3
CO2
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CONTENT
1. Model / Model Validation
i. DEF Dosing (CFD)
ii. Drive Cycle Performance (SysEng)
2. Tools and Workflows
3. Use Case
4. Summary
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SYSTEM ENGINEERING MODELDRIVER, VEHICLE, DRIVELINE ENGINE, COOLING, CONTROL …
Multi-physics model
Multi-rate numeric
Diesel Exhaust System
Dedicated coupling technique for engine thermodynamics and EAS modeling
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0D/1D DOSING MODEL
▪ Arbitrary liquid/gas mixtures
▪ Instantaneous evaporation gas phase▪ Break-up model (DEF2NH3+CO2+6H2O)
▪ Spraying liquid droplets
▪ Split is empirical parameterized or from CFD
▪ Droplets▪ Passive transport
▪ Deposition following “adsorption chemistry”
▪ Wall film▪ Heat-transfer: wall, wall film and gas phase
▪ Multi-component evaporation f(Tw, pi,g, Re)
▪ Arbitrary film reaction chemistry (i.e. decomposition of urea)
SYSTEM ENGINEERING MODELDOSING, EVAPORATION, WALL FILM …
Qz
vw
t
w
gpassi,gpassi,g
emptys,passi,depdep Zwkr
injection
surfaceu w
wutransport
wu
u b t c adecomposition
HNCO + NH3H2O
Instantaneous evaporation
transport
deposition
H2O, HNCO, NH3
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MODEL BRACK (2014*, 2016†)
▪ Rates are parameterized using experimental data from TGA measurements
▪ Translated into open User-Coding models
▪ General rate:
▪ CYA decomp. rate:
▪ HNCO evap. rate:
▪ AR, VR: estimated to match published data
▪ Validated using published data
SYSTEM ENGINEERING MODELWALL FILM – UREA DECOMPOSITION MODEL
1) CYA(s) 3 HNCO(g)2) biuret(m) urea(m) +HNCO(l)3) urea(m) +HNCO(l) biuret(m)4) urea(m) HNCO(l) +NH3(g)5) 2 biuret(m) ammelide(s) +HNCO(l) +NH36) biuret(m) +HNCO(l) CYA(s) +NH3(g)7) biuret(m) +HNCO(l) triuret(s)8) triuret(s) CYA(s) +NH3(g)9) urea(m) +2HNCO(l) ammelide(s) +H2O(g)10) biuret(m) biuret(matrix)11) biuret(matrix) biuret(m)12) biuret(matrix) 2 HNCO(g) +NH313) urea(s) urea(m)14) ammelide(s) ammelide(g)15) HNCO(l) HNCO(g)
* Brack, W.; Heine, B.; Birkhold, F.; Kruse, M.; Schoch, G.; Tischer, S. & Deutschmann, O., Chemical Engineering Science, 2014, 106, 1-8
† Brack, W.; Heine, B.; Birkhold, F.; Kruse, M. & Deutschmann, O., Emission Control Science and Technology, 2016, 1-9
biuret
triuret
cyanuric acid ammelideurea
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MODEL VS BRACK (2014)
▪ CYA decomposition▪ CYA(s) 3 HNCO(g) (0th order rate!)
▪ TGA Experiment: 6mg CYA heated at different heating rates
▪ End-of-decomposition temperature increases with increasing heating rate
▪ Good match with published data
▪ Biruet decomposition▪ All 15 reactions
▪ TGA Experiment: ~50mg biuret heated at 2K/min
▪ Initial decomposition to major amounts of CYA, minor amounts of ammelide, which, in turn decompose at higher temperatures
▪ Good match with published data
SYSTEM ENGINEERING MODELVALIDATION – CYA & BIURET DECOMPOSITION
CYA decomposition
Biuret decomposition
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MODEL VS BRACK (2016)
▪ Urea Decomposition
▪ All 15 reactions
▪ Simulation: initial urea decomposed at different constant temperatures for 180 min assuming two different film thicknesses
▪ Brack presents several contour plots gained from simulation data like the own shown here
▪ To compare them cuts at 5 temperatures were made to gather data points for comparison
SYSTEM ENGINEERING MODELVALIDATION – UREA DECOMPOSITION (SETUP)
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MODEL VS BRACK (2016)
▪ Urea Decomposition
▪ Urea mass decreases over time
▪ Fasted decomposition at highest temperature
▪ Incomplete decomposition for all temperatures, in the given time span, is in line with the reference data
▪ Effect of changing film thickness (model input parameter) is reflected accurately
▪ Reasonable qualitative agreement between simulated data from Brack and BOOST, for both cases
SYSTEM ENGINEERING MODELVALIDATION – UREA DECOMPOSITION (TOTAL MASS)
Total mass decrease
173 µm film thickness
750 µm film thickness
Points: data from contour plots x-cutsLines: BOOST simulation
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MODEL VS BRACK (2016)
SYSTEM ENGINEERING MODELVALIDATION – UREA DECOMPOSITION (SPECIES F1)
Species mass fractions
173 µm film thickness
Points: data from contour plots x-cutsLines: BOOST simulation
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MODEL VS BRACK (2016)
SYSTEM ENGINEERING MODELVALIDATION – UREA DECOMPOSITION (SPECIES F2)
Species mass fractions
750 µm film thickness
Points: data from contour plots x-cutsLines: BOOST simulation
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CONTENT
1. Model / Model Validation
i. DEF Dosing (CFD)
ii. Drive Cycle Performance (SysEng)
2. Tools and Workflows
3. Use Case
4. Summary
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EAS TOOLS –REACTION MODELING
User Coding Interface
Reaction/Transfer/Diffusion
RT-Solver /1D, 2D, 1D+1D/ for catalysts, filters, pipes, dosers,… EAS systems
𝑉 ⋅𝜕𝜌
𝜕𝑡= −
𝜕 ሶ𝑚
𝜕𝑧⋅ d𝑧 +MG𝑖 ⋅𝜈𝑖,𝑗 ⋅ ሶ𝑟𝑗 | 0 =
d𝑝
d𝑧− 𝜁 ⋅
1
2⋅ 𝜌 ⋅ 𝑣2
𝑉 ⋅𝜕𝜌 ⋅ 𝑤𝑖𝜕𝑡
= −𝜕 ሶ𝑚 ⋅ 𝑤𝑖𝜕𝑧
⋅ d𝑧 + D ⋅ 𝜌 ⋅ AC ⋅𝜕2𝑤𝑖𝜕𝑧2
⋅ d𝑧 − 𝛽 ⋅ 𝜌 ⋅ AW ⋅ 𝑤𝑖 − 𝑤𝑖,L
𝑉 ⋅𝜕𝜌 ⋅ 𝑢
𝜕𝑡= −
𝜕 ሶ𝑚 ⋅ ℎ
𝜕𝑧⋅ d𝑧 + 𝜆 ⋅ AC ⋅
𝜕2𝑇
𝜕𝑧2⋅ d𝑧 − 𝛼 ⋅ AW ⋅ 𝑇 − 𝑇W
𝑚L ⋅𝜕𝑤𝑖,L𝜕𝑡
= 𝛽 ⋅ 𝜌 ⋅ AW ⋅ 𝑤𝑖 −𝑤𝑖,L +MG𝑖 ⋅𝜈𝑖,𝑗 ⋅ ሶ𝑟𝑗
𝑚W ⋅ 𝑐p,W ⋅𝜕𝑇W𝜕𝑡
= 𝜆W ⋅ AW ⋅𝜕2𝑇𝑊𝜕𝑧2
⋅ d𝑧 + AW ⋅ 𝛼 ⋅ 𝑇 − 𝑇W +Δℎ𝑗 ⋅ ሶ𝑟𝑗 | 𝑍𝑛d𝑤𝑘,𝑛,Sd𝑡
= MG𝑘 ⋅𝜈𝑘,𝑗 ⋅ ሶ𝑟𝑚
Execution Environments
MyReac.ucp
MyTrans.ucp
MyDiff.ucp
MyModel.fmu
MyModel.zip
Kinetics/Transfer
Library• ASC: Scheuer
• LNT: Olsson
• SCR: Olsson
• SCR: Ebrahimian/Brack
• TWC: Brinkmeier
• DPF: Konstandopoulos
• CSF: Premchand
• XXX: Surface Chemkin
• …
This
study
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1D / 3D SIMULATION WORKFLOW
Tasks
Tools
Results
Component Design
3D CFD
EAS
Species uniformity, wall
film mass and
position,…
Concept Layout
Virtual Testing
1D EAS
Optimization
EAS Layout (drive cycle
emissions, component
performance,
durability….)
Reaction modeling/
parameterization
1D EAS
Coding Interface
Optimization
Model
(kinetic, transfer,
diffusion…)
Control Develepment
/Calibration
1D EAS
Control strategy
Control params.
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J.C. Wurzenberger | CDS | 14 September 2017 | 25Public
CONTENT
1. Model / Model Validation
i. DEF Dosing (CFD)
ii. Drive Cycle Performance (SysEng)
2. Tools and Workflows
3. Use Case
4. Summary
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▪ HD exhaust line
▪ Simplified Geometry
▪ Artificial mixer geometry
▪ Fame Poly Mesh
▪ 4.200.000 cells
▪ w/o wall film reactions
▪ w/ wall film evaporation
COMPONENT DESIGNDEF DOSING – MODEL SETUP
Mixer
Tg
(degC)
mg(kg/h)
mDEF(g/s)
Nr. pulses
(-)
Case 220 220 2000 2 10
Case 270 270 2000 2 10
Case 370 370 2000 2 10
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COMPONENT DESIGNDEF DOSING – 3D SIMULATION RESULTS
Urea dosing – snapshot of animation
Wall FilmCase 370
Wall FilmCase 220
Wall FilmCase 270
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DISCUSSION
▪ Most of the injected DEF vaporizes in the gas phase
▪ Wall film formation declines with increasing temperature
▪ Simulation of 10 pulse gives a trend, full steady-state is not reached
▪ Results for 1D▪ Deposition split ratio
▪ Film thickness
▪ Frozen flow field* technology enables a significant speed-up to conventional CFD
COMPONENT DESIGNDEF DOSING – 2D SIMULATION RESULTS
Wall Film Mass
0
5
10
15
20
Liq
uid
ma
ss in
jecte
d (
g)
0 2 4 6 8 10
Time (s)
9.95
20
3.8755
2.48917
0.741679
Transient_220 - Injected mass
Transient_220 - WF mass
Transient_270 - WF mass
Transient_370 - WF mass
Gas
temp.
(degC)
Mass
flow
(kg/h)
Dosing
rate
(g/s)
Nr.
pulses
Film
mass
(%)
CPU
time**
[h]
Case 220 220 2000 2 10 19.3 243
Case 270 270 2000 2 10 12.45 151
Case 370 370 2000 2 10 3.7 106
* Schellander D., Pachler K., Schmalhorst C., Nahtigal A., “Predictive Numerical Models and Methods for Selective Catalytic Reactor Applications in Diesel Powered Vehicles”, COMODIA 2017
** CPU time for 10s physical time on Linux cluster on 64 cores (less WF accumulation -> faster sim.)
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SUMMARY
▪ AT Model: DOC, injector, pipes, SCR, AMOX
▪ Engine out data from test bed (measured drive cycle)
▪ Injection mass flux: Controlled =1.1▪ Injection shut off: TSD_SCR ≥ 180°C▪ DEF split is taken from CFD▪ ~75% instantaneous evaporation
▪ ~25% wall film
▪ Passive species are deposited(= converted to surface species) in dedicated pipe
CONCEPT SIMULATIONHD EXHAUST LINE – MODEL SETUP
Start of injection@Ts(SCR) = 180°C
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SUMMARY
▪ SCR operating conditions are reached after ~120s
▪ Tailpipe NOx levels out after cold start and shows slight increase for the remaining simulation time
▪ NH3 conversion▪ SCR: 85%
▪ AMOX: 100%
▪ NOx conversation: 93%
CONCEPT SIMULATIONHD EXHAUST LINE – TAILPIPE EMISSIONS
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SUMMARY
▪ Results depend on assumed wall film thickness60 µm: avg. film thickness from CFD173 µm: moving film (Brack2016)
▪ after 60 min:
▪ thin film: less deposits, formed CYA decomposes again fully
CONCEPT SIMULATIONHD EXHAUST LINE – DEPOSIT FORMATION
dfilm / µm CYA / mg ammelide / mg Total / mg
60 - 150 150
173 320 380 700
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SUMMARY
▪ 1/3 pipe insulation lower decomposition temperatures (~25°C)
▪ after 60 min:
▪ higher total deposit mass
CONCEPT SIMULATIONHD EXHAUST LINE – DEPOSIT FORMATION
dfilm / µm CYA / mg ammelide / mg Total / mg
60 - 200 200
173 710 410 1120
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▪ 3D DEF dosing model validated in various sub-models
▪ 1D real-time, system engineering model urea decomposition model from Brack
▪ 3D-1D workflow
▪ 3D simulations provide dosing split ratio and film thickness
▪ 1D simulations show strong impact of film thickness (film surface area) on urea decomposition
SUMMARY