0D 0D/1 /1D D af afte ter-treatment treatment mo mode deling - PowerPoint PPT Presentation

0D 0D/1 /1D D af afte ter-treatment treatment mo mode deling ng with th DARS Fabian bian Mauss ss www. w.digan diganars. rs.co com

Ov Overview rview DARS 2.06: New catalyst model • Description – Application: Pt- γ -Alumina SCR – Application: Atom flow analysis – Coupling to 3D and to 1D engine codes – Usage with global chemistry – DARS 2.06: New particulate filter model • Description – Results – Future work • 2

Reactor network 1D models Complete powertrain system - possible now in DARS v2.06: - New transient 1D models: - Catalytic converter - DPF - Engine models: DARS SRM for DICI and SI engines - Cooler, pipes and turbocharging 1D models  Species tracked from inlet to exhaust  Emission optimization  CPU time efficient  Tracks inhomogeneities  Fuel flexible 3

Catalyst model Usable for: • Three way catalysts (TWC) – NOx-storage and reduction catalysts (NSC) – Diesel oxidation catalysts (DOC) – Selective catalytic reduction (SCR) – Catalyst model = 3 model-parameters: • Heat transfer parameter – Mass transfer parameter – Overall reaction efficiency – 4

Catalyst model Solution procedure - split into three levels: Detailed surface or global Heat chemistry conduction is calculated Washcoat level Several representative channels are Washcoat selected for solving: • chemistry Monolith wall • flow • heat transport • mass Channel level transport 5

Catalyst model - Channels are discretized into a number of cells: washcoat p, v, Y i , h g k+2 k-1 k k+1 Monolith wall n-2 n-1 n n+1 - Flow and chemistry calculations are decoupled - Chemistry calculations are performed in two subsections: • Bulk gas • Boundary layer 6

Catalyst model Chemistry calculation Cell bulk gas = PSR (Gas phase chemistry) • Heat & mass transfer (bulk gas - thin film layer) - modeled using • heat and mass transfer coefficients Thin layer: • • detailed surface chemistry • global gas phase chemistry Assumption: Steady state solution of the flow - in each time step • 7

Catalyst model Transient representative channel model, suitable to model Catalyst warm-up • Hot spots • Effect of site blocking / poisoning • Conversion efficiencies • Non-uniform, non-steady state inlet conditions • Effect of heat and mass transfer on conversion efficiencies • 8

Catalyst results Validation against experiments [Koop & Deutschmann, 2009] Fröjd, K., Mauss, F. - SAE 2011-01-1306 250 250 0 C 450 450 0 C The effect of C 3 H 6 inhibition on NO conversion (steady state, flat-bed reactor) 9

Catalyst results The effect of C3H6 inhibition for lean phase, 250 °C Fröjd, K., Mauss, F. - SAE 2011-01-1306 ~ 200ppm NO (according to experiment), 0.04% CO, 12% O 2 , 7% CO 2 , 10% H 2 O, balance N 2 . All measures are by volume. T = 250°C 2011-01-1306

Catalyst results The effect of C3H6 inhibition for lean phase, 250 ° Fröjd, K., Mauss, F. - SAE 2011-01-1306 2011-01-1306

Catalyst results NO mole fraction and CO site fraction (250 0 C) along the catalyst channel, as a function of distance – time Fröjd, K., Mauss, F. - SAE 2011-01-1306 12

Catalyst results NO mole fraction and CO site fraction (250 0 C) along the catalyst channel, as a function of distance – time Response time of 5.5 seconds

Catalyst results – C 3 H 6 inhibition The effect of C 3 H 6 inhibition for lean phase, 350 °C Fröjd, K., Mauss, F. - SAE 2011-01-1306 Comparison parison of mole frac action ions of spec ecie ies in bulk lk gas and d thin in film layer er for fuel el lean n compos osit itio ion, n, 90 ppm C 3 H 6 , 0.04 04 % CO. 350°C. 350 C. 2011-01-1306

Catalyst results H 2 acting as reducing agent under fuel rich conditions Fröjd, K., Mauss, F. - SAE 2011-01-1306 The e effec ect of H 2 as reduc ducing ing agent ent on NO conv nver ersio ion n under der steady eady-stat ate condition nditions in a flat at bed d reac actor or, comparison parison of exper erimen iments and simulation ulations. ~ ~ 200ppm 0ppm NO (accor ordin ding g to experimen periment), ), 60 60 ppm C 3 H 6 , 2.1% % CO, 0.9% 9% O 2 , 7% CO 2 , 10% H 2 O, balan ance N 2 . 2011-01-1306

Catalyst results: atom flow analysis Flo low paths hs for nitr itrogen ogen atoms, ms, fuel l ric ich phas ase e [Fröjd, K., Mauss, F . , Investigations of chemical processes in a NOx-storage catalyst by the use of detailed chemistry and flow analysis, ECM 2011, June 2011] 350 0 °C, 1% H 2 450 0 °C, 0% H 2 16

Catalyst results: atom flow analysis Flo low paths hs for oxyg ygen atoms ms for fuel l ric ich phas ase. e. [Fröjd, K., Mauss, F . , Investigations of chemical processes in a NOx-storage catalyst by the use of detailed chemistry and flow analysis, ECM 2011, June 2011] 350 0 °C, 1% H 2 450 0 °C, 0% H 2 . . 17 Dis isplay play lim limit: it: 0 0% of total l flu lux.

Catalyst results: atom flow analysis Flo low paths hs for hydro drogen gen atoms ms for fuel l ric ich phase. ase. [Fröjd, K., Mauss, F . , Investigations of chemical processes in a NOx-storage catalyst by the use of detailed chemistry and flow analysis, ECM 2011, June 2011] 350 0 °C, 1% H 2 450 0 °C, 0% H 2 18

Coupling to 1D engine code Cataly alyst st model el in in th the proc ocess ess to b be im imple lemented mented in in D DARS in interface ace for GT-Power Power 7.0 (DARS RS ESM). Kin inetic ic studies ies (DARS) RS) - combus mbustion ion - in in-cy cylin linde der r emis issio sion n formation mation - catalys yst emis issio sion n reduction duction AND engine gine perf rform orman ance ce analysis lysis (GT-Power) Power) 19

Calculations with global and detailed surface chemistry • Global reaction schemes are invoked via user subroutines • Detailed Surface Chemistry is invoked through Read Mechanism in DARS GUI 20

Global surface chemistry C3H6 H6 + 4 4.5O2 2 => 3 C CO2 + 3 3 H2O • Global reaction schemes describe the full conversion as one or a few lumped steps • Global reaction schemes are tuned for each catalyst type and morphology • Inhibition terms used for cross-dependency of reactants • Cannot take into account transient effects such as storage and poisoning. 21

Detailed surface chemistry NO(s (s) + Pt(s) s) <=> N(s) s) + O O(s) s) • Detailed surface chemistry includes all molecular reaction steps at the surface • Includes adsorption, reactions at the surface (Langmuir-Hinshelwood reactions), reactions of gas phase species with surface species (Eley-Rideal reactions), desorption. • Invoked through Read Mechanism in DARS GUI • Species storage is modeled. Thus transient effects such as oxygen storage in TWC’s and poisoning can be modeled. • Can be combined with global rates for conversion. • Example: oxygen storage model combined with global rate for CO, NO and HC conversion in TWC 22

Global reaction rate optimization Define test matrix 1. 1. Isolation of reaction rates: Tuning for CO, HC and NO conversion separately 2. Combinations representing the possible exhaust gas compositions 3. Temperature ramp for transient conditions / temperature matrix 500 T [°C] 450 400 Temperature [°C] 350 300 250 200 150 100 50 0 0 200 400 600 800 1000 1200 time [s] 23

Global reaction rate optimization Optimization (e.g. Matlab) 2. Validation for engine cycle 3. DARS Catalyst calculation(s) Usage: parameter studies 4. Effect of catalyst length on – emission conversion Effects of exhaust emission – levels on conversion Improved rate Outlet parameters concentrations Transient crossdependencies – between species. Coupling to SRM in-cylinder – model to study overall gain of in-cylinder parameters (EGR Evaluation of rate, equivalence ratio, …) results 24

Diesel Particulate Filter (DPF) model DPF DICI- SRM 25

DPF model The solution procedure is split into three levels: Soot deposition and oxidation Heat conduction is calculated Porous media Reactor level and soot cake leve Solved: • soot deposition and Soot cake oxidation Porous wall • pressure drop and flow properties • chemistry • heat transport Channel level 26

DPF model Soot cake Porous wall  Pressure drop and flow between inlet and outlet channels - modeled by Darcy’s law  Permeability - calculated from the current level of soot deposited in soot cake and in the filter 27

DPF model Soot deposition is modeled by unit cell filtration model [Konstandopoulos, A.G. et al., SAE 2000-01-1016] Also calculated: Soot cake growth • Soot oxidation • Catalytic reactions in wall • Heating of wall • Interaction between soot cake and catalytic reaction paths • Heat conduction throughout the filter • 28

DPF results Flow velocities and pressure in the DPF channel 29

DPF results Filter er wall permeabil ability ty and collec ection ion efficiency iency 30

Future work Currently coupling to STAR • Currently coupling to GT-Power • Built-in setup for different catalyst types • – TWC (chemistry available) – DOC (Pt- γ -Alumina chemistry available) – SCR 31