NOX ABATEMENT. 1D/3D simulation of urea dosing and selective catalytic reduction

Transcription

1 NOX ABATEMENT 1D/3D simulation of urea dosing and selective catalytic reduction J. C. Wurzenberger, A. Nahtigal, T. Mitterfellner, K. Pachler, S. Kutschi AVL List GmbH (Headquarters)

2 BACKGROUND 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 J.C. Wurzenberger CDS 14 September

3 DEPOSITS DEPEND ON: 1. DESIGN 2. INJECTOR 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. 3. BOUNDARY CONDITIONS J.C. Wurzenberger CDS 14 September

4 CONTENT 1. Model / Model Validation i. DEF Dosing (CFD) ii. Drive Cycle Performance (SysEng) 2. Tools and Workflows 3. Use Case 4. Summary J.C. Wurzenberger CDS 14 September

5 DEF DOSING INJECTION OF UREA-WATER SOLUTION SPRAY PREPARATION MODELS Injection of urea-water solution Urea-water properties: f(t,w i,g ) Nozzle modeling J.C. Wurzenberger CDS 14 September

6 DEF DOSING SPRAY/GAS INTERACTION SPRAY PREPARATION MODELS I. II. II. III. III. H 0 2 (NH ) CO 22 (NH ) CO (g) 22 (NH ) CO (s or l) 22 (NH 2 ) 2 CO NH 3 H 2 O HNCO NH 3 CO 2 (NH ) CO (g) 22 (NH ) CO (s or l) 22 Injection of urea-water solution Urea-water properties: f(t,w i,g ) Nozzle modeling Spray/gas interaction Multicomponent evaporation Thermolysis: (NH2)2CO NH3 + HNCO Hydrolysis: HNCO + H2O NH3 + CO2 H 0 (l) 2 (NH 22 ) CO H (s 0 or (l) l) 2 (NH ) CO (s or l) 22 H 0 (l) 2 H20 (l) H 0 (g) 2 (NH 22 ) CO H 0 (g) (g) 2 (NH ) CO (g) 22 H 0 (g) 2 H 0 (g) 2 NH (g) + HNCO (g) 3 NH (g) + HNCO (g) 3 J.C. Wurzenberger CDS 14 September

7 DEF DOSING SPRAY/GAS INTERACTION SPRAY PREPARATION MODELS Velocity (NH 2 ) 2 CO NH 3 H 2 O HNCO NH 3 NH 3 CO 2 Injection of urea-water solution Urea-water properties: f(t,w i,g ) Nozzle modeling Spray/gas interaction Multicomponent evaporation Thermolysis: (NH2)2CO NH3 + HNCO Hydrolysis: HNCO + H2O NH3 + CO2 Uni=0.84 =0.94 J.C. Wurzenberger CDS 14 September

8 DEF DOSING SPRAY/WALL INTERACTION SPRAY PREPARATION MODELS (NH 2 ) 2 CO NH 3 H 2 O HNCO NH 3 CO 2 Injection of urea-water solution Urea-water properties: f(t,w i,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 J.C. Wurzenberger CDS 14 September

9 DEF DOSING SPRAY/WALL INTERACTION -- VALIDATION Test bench at Graz University of Technology Nahtigal et al. SCR recent development and method, AVL International Simulation Conference, 2017 J.C. Wurzenberger CDS 14 September

10 DEF DOSING COOLING OF WALLS SPRAY PREPARATION MODELS Injection of urea-water solution Urea-water properties: f(t,w i,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, ) J.C. Wurzenberger CDS 14 September

11 DEF DOSING CATALYTIC CONVERSION SPRAY PREPARATION MODELS (NH 2 ) 2 CO NH 3 H 2 O HNCO NH 3 CO 2 Injection of urea-water solution Urea-water properties: f(t,w i,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, J.C. Wurzenberger CDS 14 September

12 CONTENT 1. Model / Model Validation i. DEF Dosing (CFD) ii. Drive Cycle Performance (SysEng) 2. Tools and Workflows 3. Use Case 4. Summary J.C. Wurzenberger CDS 14 September

13 SYSTEM ENGINEERING MODEL DRIVER, VEHICLE, DRIVELINE ENGINE, COOLING, CONTROL Multi-physics model Multi-rate numeric Diesel Exhaust System Dedicated coupling technique for engine thermodynamics and EAS modeling J.C. Wurzenberger CDS 14 September

14 SYSTEM ENGINEERING MODEL DOSING, EVAPORATION, WALL FILM 0D/1D DOSING MODEL injection Instantaneous evaporation u g wi,pass g w t z transport w H 2 O, HNCO, NH 3 transport u i,pass w v r g u w dep Q k H 2 O dep u surface w HNCO + NH 3 decomposition b t c a i,pass Z deposition s, empty Arbitrary liquid/gas mixtures Instantaneous evaporation gas phase Break-up model (DEF 2NH3+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(t w, p i,g, Re) Arbitrary film reaction chemistry (i.e. decomposition of urea) J.C. Wurzenberger CDS 14 September

15 SYSTEM ENGINEERING MODEL WALL 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) +NH3 6) 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) +NH3 13) urea(s) urea(m) 14) ammelide(s) ammelide(g) 15) HNCO(l) HNCO(g) 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: A R, V R : estimated to match published data biuret urea cyanuric acid ammelide Validated using published data triuret * 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 J.C. Wurzenberger CDS 14 September

16 SYSTEM ENGINEERING MODEL VALIDATION CYA & BIURET DECOMPOSITION CYA decomposition MODEL VS BRACK (2014) Biuret decomposition 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 J.C. Wurzenberger CDS 14 September

17 SYSTEM ENGINEERING MODEL VALIDATION UREA DECOMPOSITION (SETUP) 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 J.C. Wurzenberger CDS 14 September

18 SYSTEM ENGINEERING MODEL VALIDATION UREA DECOMPOSITION (TOTAL MASS) Total mass decrease 173 µm film thickness 750 µm film thickness Points: data from contour plots x-cuts Lines: BOOST simulation 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 J.C. Wurzenberger CDS 14 September

19 SYSTEM ENGINEERING MODEL VALIDATION UREA DECOMPOSITION (SPECIES F1) Species mass fractions 173 µm film thickness MODEL VS BRACK (2016) Points: data from contour plots x-cuts Lines: BOOST simulation J.C. Wurzenberger CDS 14 September

20 SYSTEM ENGINEERING MODEL VALIDATION UREA DECOMPOSITION (SPECIES F2) Species mass fractions 750 µm film thickness MODEL VS BRACK (2016) Points: data from contour plots x-cuts Lines: BOOST simulation J.C. Wurzenberger CDS 14 September

21 CONTENT 1. Model / Model Validation i. DEF Dosing (CFD) ii. Drive Cycle Performance (SysEng) 2. Tools and Workflows 3. Use Case 4. Summary J.C. Wurzenberger CDS 14 September

22 EAS TOOLS REACTION MODELING User Coding Interface Reaction/Transfer/Diffusion MyReac.ucp MyTrans.ucp MyDiff.ucp Kinetics/Transfer Library ASC: Scheuer LNT: Olsson SCR: Olsson SCR: Ebrahimian/Brack TWC: Brinkmeier DPF: Konstandopoulos CSF: Premchand XXX: Surface Chemkin This study Execution Environments MyModel.fmu MyModel.zip V ρ t = mሶ z dz + MG i ν i,j r j ሶ V ρ w i = mሶ w i t z ρ u V = mሶ h t z m L w i,l t m W c p,w T W t 0 = dp dz ζ 1 ρ v2 2 dz + D ρ A C 2 w i z 2 dz β ρ A W w i w i,l dz + λ A C 2 T z 2 dz α A W T T W = β ρ A W w i w i,l + MG i ν i,j r j ሶ = λ W A W 2 T W z 2 dz + A dw k,n,s W α T T W + Δh j r j ሶ Z n = MG dt k ν k,j r m ሶ RT-Solver /1D, 2D, 1D+1D/ for catalysts, filters, pipes, dosers, EAS systems J.C. Wurzenberger CDS 14 September

23 1D / 3D SIMULATION WORKFLOW Tasks Reaction modeling/ parameterization Concept Layout Virtual Testing Component Design Control Develepment /Calibration Tools 1D EAS Coding Interface Optimization 1D EAS Optimization 3D CFD EAS 1D EAS Results Model (kinetic, transfer, diffusion ) EAS Layout (drive cycle emissions, component performance, durability.) Species uniformity, wall film mass and position, Control strategy Control params. J.C. Wurzenberger CDS 14 September

24 CONTENT 1. Model / Model Validation i. DEF Dosing (CFD) ii. Drive Cycle Performance (SysEng) 2. Tools and Workflows 3. Use Case 4. Summary J.C. Wurzenberger CDS 14 September

25 COMPONENT DESIGN DEF DOSING MODEL SETUP HD exhaust line Mixer Simplified Geometry Artificial mixer geometry Fame Poly Mesh cells w/o wall film reactions Tg (degc) m g (kg/h) m DEF (g/s) Nr. pulses (-) w/ wall film evaporation Case Case Case J.C. Wurzenberger CDS 14 September

26 COMPONENT DESIGN DEF DOSING 3D SIMULATION RESULTS Urea dosing snapshot of animation Wall Film Case 220 Wall Film Case 270 Wall Film Case 370 J.C. Wurzenberger CDS 14 September

27 Liquid mass injected (g) COMPONENT DESIGN DEF DOSING 2D SIMULATION RESULTS Transient_220 - Injected mass Transient_220 - WF mass Transient_270 - WF mass Transient_370 - WF mass Wall Film Mass Time (s) Gas temp. (degc) Mass flow (kg/h) Dosing rate (g/s) Nr. pulses Film mass (%) CPU time** [h] 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 Case Case Case Frozen flow field* technology enables a significant speed-up to conventional CFD ** CPU time for 10s physical time on Linux cluster on 64 cores (less WF accumulation -> faster sim.) * Schellander D., Pachler K., Schmalhorst C., Nahtigal A., Predictive Numerical Models and Methods for Selective Catalytic Reactor Applications in Diesel Powered Vehicles, COMODIA 2017 J.C. Wurzenberger CDS 14 September

28 CONCEPT SIMULATION HD EXHAUST LINE MODEL SETUP SUMMARY Start of s (SCR) = 180 C 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: T SD_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 J.C. Wurzenberger CDS 14 September

29 CONCEPT SIMULATION HD EXHAUST LINE TAILPIPE EMISSIONS 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% J.C. Wurzenberger CDS 14 September

30 CONCEPT SIMULATION HD EXHAUST LINE DEPOSIT FORMATION SUMMARY Results depend on assumed wall film thickness 60 µm: avg. film thickness from CFD 173 µm: moving film (Brack2016) after 60 min: d film / µm CYA / mg ammelide / mg Total / mg thin film: less deposits, formed CYA decomposes again fully J.C. Wurzenberger CDS 14 September

31 CONCEPT SIMULATION HD EXHAUST LINE DEPOSIT FORMATION SUMMARY 1/3 pipe insulation lower decomposition temperatures (~25 C) after 60 min: d film / µm CYA / mg ammelide / mg Total / mg higher total deposit mass J.C. Wurzenberger CDS 14 September

32 SUMMARY 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 J.C. Wurzenberger CDS 14 September