Digital Analysis of Reactive Systems Introduction DARS is a complex - - PowerPoint PPT Presentation

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

• ptimize 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

INPUT

Heat release Mass fraction burned

1D- CODE

Flow Temperatures Performance parameters

OUTPUT Deterministic INPUT

DARS- 1D

Flow Temperatures Performance parameters

OUTPUT

Engine Parameters Mixing time Unburned hydrocarbons Soot NOx

Predictive

13

Stochastic Reactor Model

DI-SRM

14

Stochastic Reactor Model

15

PDF = Probability Density Function

• The mixture is represented by a

PDF in phase-space

• In-cylinder mass is divided into

particles realizing the distributions

• Each particle represents a point in

phase space for species mass fraction and enthalpy The 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

5 10 15 20 25 30 6,0 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] Pressure [MPa]

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

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

p, v, Yi, , hg

Ci,

i,p,

, Γm, , Ѳm,

m,j ,T

,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

• utlet 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: CD: DARS-CFD CFD Spec ecies ies Yi En Enthalpy halpy h Spec ecies ies Yi

*

Transpo ansport rt data Dij

ij,

, l, , n

TIF

STAR-CD – TIF coupling

2 2

2

i i i i

Y Y W t Z          

STAR-CD CD Transpo ansport rt of Z, Z”2, h, I Updat date e h and and  Get cell ll lo local l T and and Wq Perf rform

• rm specie

cies s pdf in integra rati tion

• n

Z, Z”2 T, W Wq Yi(Z) 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

cm-sec-K

Gas Inlet

X(CO) = 0.1mol% O2/CO = 0.5 u = 0.5 m/s T = 420K P = 1 atm.

35

Summary NOx Results

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!