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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!