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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-

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SLIDE 1

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

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SLIDE 2

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  • DARS 2.06: New catalyst model

–

Description

–

Application: Pt-γ-Alumina SCR

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Application: Atom flow analysis

–

Coupling to 3D and to 1D engine codes

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Usage with global chemistry

  • DARS 2.06: New particulate filter model

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Description

–

Results

  • Future work

Ov Overview rview

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SLIDE 3

Reactor network 1D models

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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
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SLIDE 4

Catalyst model

  • Usable for:

–

Three way catalysts (TWC)

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NOx-storage and reduction catalysts (NSC)

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Diesel oxidation catalysts (DOC)

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Selective catalytic reduction (SCR)

  • Catalyst model = 3 model-parameters:

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Heat transfer parameter

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Mass transfer parameter

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Overall reaction efficiency

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SLIDE 5

Catalyst model

Solution procedure - split into three levels:

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Washcoat Monolith wall

Channel level Washcoat level

Heat conduction is calculated

Several representative channels are selected for solving:

  • chemistry
  • flow
  • heat transport
  • mass

transport

Detailed surface or global chemistry

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SLIDE 6

Catalyst model

6 n-1 n n+1 n-2 k-1 k k+1 k+2

p, v, Yi, hg

washcoat Monolith wall

  • Channels are discretized into a number of cells:
  • Flow and chemistry calculations are decoupled
  • Chemistry calculations are performed in two

subsections:

  • Bulk gas
  • Boundary layer
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SLIDE 7

Catalyst model

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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
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SLIDE 8

Catalyst model

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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
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SLIDE 9

Catalyst results

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Validation against experiments [Koop & Deutschmann, 2009]

Fröjd, K., Mauss, F. - SAE 2011-01-1306

250 2500C 450 4500C

The effect of C3H6 inhibition on NO conversion (steady state, flat-bed reactor)

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SLIDE 10

Catalyst results

The effect of C3H6 inhibition for lean phase, 250 °C

Fröjd, K., Mauss, F. - SAE 2011-01-1306 2011-01-1306

~ 200ppm NO (according to experiment), 0.04% CO, 12% O2, 7% CO2, 10% H2O, balance N2. All measures are by volume. T = 250°C

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SLIDE 11

Catalyst results

The effect of C3H6 inhibition for lean phase, 250 °

Fröjd, K., Mauss, F. - SAE 2011-01-1306 2011-01-1306

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SLIDE 12

Catalyst results

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

Fröjd, K., Mauss, F. - SAE 2011-01-1306

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SLIDE 13

Catalyst results

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

Response time of 5.5 seconds

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SLIDE 14

2011-01-1306

The effect of C3H6 inhibition for lean phase, 350 °C

Catalyst results – C3H6 inhibition

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

  • sit

itio ion, n, 90 ppm C3H6, 0.04 04 % CO. 350 350°C. C.

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SLIDE 15

2011-01-1306

H2 acting as reducing agent under fuel rich conditions

Catalyst results

The e effec ect of H2 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

  • r, comparison

parison of exper erimen iments and simulation ulations. ~ ~ 200ppm 0ppm NO (accor

  • rdin

ding g to experimen periment), ), 60 60 ppm C3H6, 2.1% % CO, 0.9% 9% O2, 7% CO2, 10% H2O, balan ance N2.

Fröjd, K., Mauss, F. - SAE 2011-01-1306

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SLIDE 16

Catalyst results: atom flow analysis

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Flo low paths hs for nitr itrogen

  • gen atoms,

ms, fuel l ric ich phas ase e 350 0 °C, 1% H2 450 0 °C, 0% H2

[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]

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SLIDE 17

Catalyst results: atom flow analysis

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350 0 °C, 1% H2 450 0 °C, 0% H2. . Dis isplay play lim limit: it: 0 0% of total l flu lux. 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]

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SLIDE 18

Catalyst results: atom flow analysis

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350 0 °C, 1% H2 450 0 °C, 0% H2 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]

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SLIDE 19

Coupling to 1D engine code

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Cataly alyst st model el in in th the proc

  • cess

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

  • rman

ance ce analysis lysis (GT-Power) Power)

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SLIDE 20

Calculations with global and detailed surface chemistry

20

  • Global reaction schemes are

invoked via user subroutines

  • Detailed Surface Chemistry is

invoked through Read Mechanism in DARS GUI

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SLIDE 21

Global surface chemistry

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  • 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.

C3H6 H6 + 4 4.5O2 2 => 3 C CO2 + 3 3 H2O

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SLIDE 22

Detailed surface chemistry

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  • 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

NO(s (s) + Pt(s) s) <=> N(s) s) + O O(s) s)

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SLIDE 23

Global reaction rate optimization

1.

Define test matrix

  • 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

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50 100 150 200 250 300 350 400 450 500 200 400 600 800 1000 1200 Temperature [°C] time [s] T [°C]

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SLIDE 24

Global reaction rate optimization

2.

Optimization (e.g. Matlab)

3.

Validation for engine cycle

4.

Usage: parameter studies

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Effect of catalyst length on emission conversion

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Effects of exhaust emission levels on conversion

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Transient crossdependencies between species.

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Coupling to SRM in-cylinder model to study overall gain of in-cylinder parameters (EGR rate, equivalence ratio, …)

24 DARS Catalyst calculation(s) Outlet concentrations Evaluation of results Improved rate parameters

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SLIDE 25

Diesel Particulate Filter (DPF) model

DPF

25 DICI- SRM

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SLIDE 26

Reactor level

Porous wall

Channel level

Soot cake

Porous media and soot cake leve

DPF model

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The solution procedure is split into three levels:

Heat conduction is calculated Soot deposition and oxidation Solved:

  • soot

deposition and

  • xidation
  • pressure drop

and flow properties

  • chemistry
  • heat transport
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SLIDE 27

DPF model

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Porous wall

Soot cake

  • Pressure drop and flow between inlet and
  • utlet channels - modeled by Darcy’s law
  • Permeability - calculated from the current

level of soot deposited in soot cake and in the filter

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SLIDE 28

Soot deposition is modeled by unit cell filtration model 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

DPF model

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[Konstandopoulos, A.G. et al., SAE 2000-01-1016]

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SLIDE 29

DPF results

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Flow velocities and pressure in the DPF channel

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SLIDE 30

DPF results

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

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SLIDE 31

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

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