DARS

Digital Analysis of Reactive Systems

Introduction

DARS is a complex chemical reaction analysis

system, developed by DigAnaRS.

Our latest version, DARS V2.0, was released in

September 2008 and new releases are planned every 4

months.

You’ll find more details at www.DigAnaRS.com

The DARS suite consists of the following

components» DARS Basic

» DARS LGT

» DARS CFD

» DARS ESM

What DARS Basic can do

Import Chemkin format mechanisms and view, analyze, reduce and export chemical kinetics for fluid and surface reactions.

Simulate simple 0-D reactors, 0-D engine models and 1-D reaction fronts.

Generate kinetic landscapes for ignition delays times;• Looping is supported for pressure, temperature, fuel-air equivalence ratio and

artificial EGR

• Kinetic mapping is accelerated through multiprocessor usage.

• Multiprocessor options are offered as beneficial HPC licenses.

Simulate Stochastic Reactor engine models.• HCCI, SI and DI models are available in DARS v 2.00.

Simulate simple reactor networks like 0-D models.• Our first reactor networks are available as command line models.

Analyse results with the Graph Comparator.

Export validated and tested mechanisms for usage with CFD or ESM tools.

More information about DARS Basic

Supports gas phase chemistry and surface chemistry• Allows definition of up to 10 surfaces.

Highly robust stiff solver• Both time dependent and steady state solutions.

Includes data bases of physical properties• Thermophysical data (specific heat, enthalpy, entropy)

• Transport properties (viscosity, thermal conductivity, diffusivity)

Includes sophisticated ideal flame models

• 1-D reactor: Flamelet, Opposed Flame, Premixed Burner Stabilized Flame and

Freely Propagating Flame.

Can perform analyses of reaction mechanisms

– Sensitivity analysis, Reaction flow analysis, Necessity analysis, and Life time

analysis

Has a highly efficient mechanism reduction module

More information about DARS Basic

Includes sophisticated ideal reactor models

• 0-D reactor: Perfectly Stirred Reactor, Plug Flow Reactor, Constant Volume

reactor, Constant Pressure reactor, HCCI engine model, SI engine model.

• Multiple reactor definitions possible for kinetic map generation.

Can exports mechanism data to STAR-CD, GT-POWER and

WAVE

The DARS Basic Interface is intuitive and user-friendly

The mechanism analyses in DARS Basic

• Sensitivity analysis

• Flow analysis

• Necessity analysis

• Lifetime analysis

DARS-Basic (Reduction)

Reducing mechanisms using DARS Basic

• The reduction module uses

reactor calculations to

optimize the mechanism

• Results can easily be

compared with detailed or

with other reduced

chemistry calculations

Exporting mechanism using DARS Basic

™

• Mechanisms can be exported in

several different formats, for

instance:

CHEMKINTM format

Fortran 95 modules

• Allows using the

chemistry in any

software

Compiled .dll/.so files

• Allows using the

chemistry in any

software that is

compatible with DARS

Future development plans for DARS Basic

Extended engine models

• Multi zone models.

• Engine performance optimization.

• Usage of library based models (Flamelet, TPFM)

Development of reactor networks

• Simple engine models (Inlet system, engine model, exhaust system, EGR system)

Visual reduction, through the DARS reaction flux filter technique.

Fully support looping for reaction front calculations.

Full soot model support

Overview 1D-project

DI-SRM

Intake valve

Exhaust valve

Catalyst

DPF

12

Standard tools vs DARS-1D

INPUTHeat releaseMass fraction burned 1D-

CODE

FlowTemperaturesPerformance parameters

OUTPUT

DeterministicINPUT

DARS-

1D

FlowTemperaturesPerformance parameters

OUTPUTEngine ParametersMixing time

Unburned hydrocarbonsSootNOx

Predictive

13

Stochastic Reactor Model

DI-SRM

14

Stochastic Reactor Model

15

PDF = Probability Density Function

• The mixture is represented by aPDF in phase-space

• In-cylinder mass is divided intoparticles realizing the

distributions

• Each particle represents a point in phase space for species mass

fractionand enthalpyThe SRM captures

inhomogeneities in the

cylinder

Stochastic Reactor Model

Fuel mixes with cylinder gas at injection

16

fuel

air in cylinder

EGR

Fuel is injected into the cylinder

Portions of the cylinder gas is taken for evaporation

New particles containing fuel and cylinder gas are created

The mixing is controlled by

the τ curve

Stochastic Reactor Model

17

Pressure history variations

Pasternak et al, SAE 2009-01-0676

-10 -5 0 5 10 15 20 25 306,0

7,0

8,0

9,0

10,0

11,0

12,0

13,0

14,0

15,0

16,0

Exp

Sim, Cycle 61-110

Sim, Average 10 cycles

Sim, Average 20 cycles

Sim, Average 30 cycles

Sim, Average 50 cycles

Crank Angle [deg ATDC]

Pre

ssure

[M

Pa]

Average values from simulated cycles

Catalyst

Catalyst

18

Catalyst

Several problems need to be adressed when simulating a

catalyst.

• Heat and mass transfer between bulk gas and surface

• Surface reactions

• Gas phase reactions

• Diffusion in pores

• Heat conduction in surface

• Heat conduction in substrate

19

Catalyst

The solution procedure is split into three levels

20

Reactor level

Washcoat

Monolith wall

Channel level

Washcoat level

Heat conduction is

calculated

Several representative

channels are selected for

solving of

• chemistry

• flow

• heat transport

• mass transport

Detailed or global

chemistry

Catalyst

21

n-1 n n+1n-2

k-1 k k+1 k+2

p, v, Yi, hg

Ci,p, Γm, Ѳm,j ,Tw

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 (pores and wall

surface)

Catalyst

22

Chemistry calculation• Series of perfectly stirred reactors

• Heat and mass transfer between bulk gas and thin film layer are

modeled using heat and mass transfer coefficients

• Detailed chemistry or global gas phase chemistry can be used

• Gas phase chemistry in bulk gas can be modeled

Assumption made for the flow• Steady state solution for the flow calculated in each time step

Catalyst

23

Validation against Koop, J., Deutschmann, O.,

Applied Catalysis B: Environmental 91 (2009) 47–58

DPF

DPF

24

Reactor level

Porous wall

Channel level

washcoat

Soot

cake

Porous media

and soot cake level

DPF

25

The solution procedure is split into three levels

Heat conduction is

calculated

Detailed or global

chemistry

Several representative

channels are selected for

solving of

• chemistry

• flow

• heat transport

• mass transport

DPF

26

Porous wall

washcoat

Soot cake

Flow between inlet and

outlet channels are modeled

using Darcy’s law

calculating pressure drop

DARS Library Generation Tool (LGT)

DARS LGT contains the following features:

Library Generation Tool for zero-dimensional ignition timing

(ECFM) and progress variable based models.

Looping can be performed together with DARS Basic.

Library generation tool for one-dimensional stationary and

transient flamelets (TFLM).

Library generation tool for flame velocities.

Future development of DARS LGT includes:

Library generation tool for flame velocities.

DARS Computational Fluid Dynamics (CFD)

DARS CFD contains the following features:

Fast coupled ODE and algebraic chemistry solver.

Coupling of detailed/reduced chemistry models with a CFD

program.

Multiprocessor options are offered as beneficial HPC

licenses.

Future development of DARS CFD:

Full particle model support.

Inclusion of monitoring cells for reaction flow and sensitivity

analysis.

DARS-CFD – STAR-CD coupling

STAR-CD:

DARS-CFD

Species Yi0

Enthalpy hSpecies Yi

* Transport data Dij, l, n

TIF

STAR-CD – TIF coupling

2

22

i ii i

Y YW

t Z

STAR-CD

Transport of Z, Z”2, h, I

Update h and Get cell local T and Wq

Perform species pdf integration

Z, Z”2 T, Wq

Yi(Z)

31

Flamelet library based emission models

• Soot

– Method of Moments

– Sectional Method

• NOx

Reduction of pollutant species

• NOx, SOx, Soot, Unburned Hydrocarbon in flames

Catalyst reaction

• Catalyst combustion

• Fuell cell reformer

• deNOx, deSOx on catalyst

Chemical vapor deposition

• Silicon epitaxial film

• Metal Organic Compound

Other important process

• Partially oxidation of hydrocarbon

• Pyrolysis of hydrocarbon

Application of DARS-CFD to reacting-flow

Problem description:

X(CO) = 0.1

O2/CO = 0.5

u = 0.5 m/s,

1m/s

T = 420K

P = 1 atm.

Monolith single channel

1 mm

10 mm

Three way catalyst

(k = A T**b exp(-E/RT)) SURFACE REACTIONS CONSIDERED A b E 1. O2+2PT(S)=>2O(S) 7.00E-02 0.0 0.0 Coefficients are sticking parameters... 2. 2O(S)=>O2+2PT(S) 9.25E+24 0.0 213200.0 Coverage parameters for species O(S): 0.000E+00 0.000E+00-6.000E+04 3. CO+PT(S)=>CO(S) 8.40E-01 0.0 0.0 Coefficients are sticking parameters... 4. CO(S)=>CO+PT(S) 2.50E+16 0.0 125500.0 Coverage parameters for species CO(S): 0.000E+00 0.000E+00-3.300E+04 5. CO2(S)=>CO2+PT(S) 2.50E+16 0.0 20500.0 6. CO(S)+O(S)=>CO2(S)+PT(S) 9.25E+23 0.0 105000.0 Coverage parameters for species CO(S): 0.000E+00 0.000E+00-3.300E+04 NOTE: E units Joules/mol, A units mole-cm-sec-K

Gas

InletX(CO) = 0.1mol%

O2/CO = 0.5

u = 0.5 m/s

T = 420K

P = 1 atm.

35

Summary NOx Results

0

10

20

30

40

50

60

E0 E1 F0 F1 F2

Experiment

Lib-NOx

36

Summary Soot Results

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

E0 E1 F0 F1 F2

Experiment

SCt = 0.5

SCt = 0.6

Secondary Air Combustion (DARS-CFD)

DARS 2.0 - Summary

DARS includes capabilities for chemistry development:

• Mechanism analysis via several 0-D and 1-D models

• Mechanism reduction

• Mechanism optimization

DARS facilitates use of chemical models in:

• 1-D engine simulation software (HCCI, SI, Diesel)

• 3-D computational fluid dynamics software

» Fast solver for 0-D treatment of chemistry

» Flamelet libraries

» Transient interactive flamelets

The DARS team can quickly respond to customer

requests and format needs!