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: CHEMKIN TM 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 Intake Exhaust valve valve Catalyst DI-SRM DPF 12
Standard tools vs DARS-1D INPUT OUTPUT 1D- Heat release Flow Mass fraction burned Temperatures Performance parameters CODE Deterministic INPUT OUTPUT DARS- Engine Parameters Flow Mixing time Temperatures Performance parameters 1D Unburned hydrocarbons Predictive Soot NOx 13
Stochastic Reactor Model DI-SRM 14
Stochastic Reactor Model 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 15
Stochastic Reactor Model Fuel mixes with cylinder gas at injection fuel air in cylinder EGR New particles containing Fuel is injected into Portions of the cylinder gas fuel and cylinder gas are the cylinder is taken for evaporation created The mixing is controlled by the τ curve 16
Stochastic Reactor Model Pressure history variations Pasternak et al, SAE 2009-01-0676 16,0 15,0 14,0 Pressure [MPa] 13,0 12,0 11,0 10,0 Exp Sim, Cycle 61-110 9,0 Sim, Average 10 cycles 8,0 Sim, Average 20 cycles Sim, Average 30 cycles 7,0 Sim, Average 50 cycles 6,0 -10 -5 0 5 10 15 20 25 30 Crank Angle [deg ATDC] Average values from simulated cycles 17
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 Heat conduction is Detailed or global calculated chemistry Washcoat level Reactor level Washcoat Several representative channels are selected for solving of Monolith wall • chemistry • flow Channel level • heat transport 20 • mass transport
Catalyst Channels are discretized into a number of cells C i, i,p , , Γ m , , Ѳ m, m,j ,T ,T w 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 (pores and wall surface) 21
Catalyst 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 • 22
Catalyst Validation against Koop, J., Deutschmann, O., Applied Catalysis B: Environmental 91 (2009) 47 – 58 23
DPF DPF 24
DPF The solution procedure is split into three levels Heat conduction is Detailed or global calculated chemistry Porous media Reactor level and soot cake level Soot cake Porous wall Several representative channels are selected for solving of • chemistry washcoat • flow Channel level • heat transport 25 • mass transport
DPF Soot cake Porous wall washcoat Flow between inlet and outlet channels are modeled using Darcy’s law calculating pressure drop 26
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: Spec ecies ies Y i 0 , l , , n Spec ecies ies Y i * Transpo ansport rt data D ij ij , En Enthalpy halpy h DARS-CFD CFD
STAR-CD – TIF coupling STAR-CD CD Transpo ansport rt of Z, Z” 2 , h, I T, W W q Z, Z” 2 Get cell ll lo local l T and and W q and Updat date e h and Perf rform orm specie cies s pdf in integra rati tion on Y i (Z) Z) 2 Y Y TIF i i W i i 2 t 2 Z
Flamelet library based emission models Soot • – Method of Moments – Sectional Method NOx • 31
Application of DARS-CFD to reacting-flow 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 •
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