DARS FUEL MODEL DEVELOPMENT

Transcription

1 DARS FUEL MODEL DEVELOPMENT

2 DARS Products (names valid since October 2012) DARS 0D & 1D tools Old name: DARS Basic DARS Reactive Flow Models tools for 3D/ CFD calculations DARS Fuel New! Advanced fuel models Stand alone tool for 0D-1D analyses of chemical processes in industrial and scientific devices - Chemistry module coupled to CFD (STAR-CD and STAR-CCM+) - Gas phase chemistry and surface chemistry - TIF: Transient interactive flamelet model coupled to STAR-CD - Libraries and run-time reaction mechanisms for detailed chemistry modeling in conjunction with DARS CFD/TIF 2

3 DARS (Basic) Flames Reactors DARS 1D Models Chemical Mechanisms Burner stabilized Homogeneous CV SRM (Stochastic Reactor Models) Coolers Turbo charging Development Analysis Counter Flow PSR PSR Piping After-treatment Reduction Freely propagating RCM SRM-HCCI Flamelet CP SRM SI Catalytic Converter SRM-Diesel Particulate Filter (DPF) 3

4 EXAMPLE FOR FUEL MODEL DEVELOPMENT WITH DARS

5 Outline Ethanol-gasoline blend selection Ethanol-gasoline chemical mechanism DARS mechanism analysis Sensitivity analysis Flow analysis Necessity analysis Life time analysis DARS mechanism reduction Ethanol-gasoline dual fuel table generation

6 ETHANOL-GASOLINE BLEND SELECTION 6

7 Aspects of surrogate fuel choice Real fuels are not consisting of one single component The surrogate chemistry needs to be representative of the components present in the real fuel Physical properties and chemical properties need to be matched Example: ethanol-gasoline fuel mixture Standards: DIN EN 228, SS E5/E10: unleaded gasoline with 5/10% ethanol E75/85: Winter/summer mixture containing 75/85% ethanol Gasoline E5 E10 E75 E85 RON 95* ** Density (kg/m3) Aromatic content (%v/v) Lower heating value (MJ/kg): ** Note: * The base gasoline used for mixing might be of varying quality for different mixtures ** Reported octane numbers for E75/85 are approximations 7

8 Methodology Find a base gasoline composition which conforms to aromatic content, as well as density, lower heating value and RON when mixed with 5% ethanol. RON calculations: Modified Linear by Volume (MLbV) [1]: Good approximation for synergetic blending of iso-octane, n-heptane and toluene. Linear by Mole Fraction (LbMF) [2]: Shown to yield good results for gasoline/ethanol blends. Calculate RON for the gasoline based on the MLbV method, and the effect of the added ethanol by the LbMF method. Calculated liquid volume fraction Calculated gaseous mole fraction A1CH I-C8H N-C7H

9 Lower heating value (MJ/kg) Heat of vaporization [J/kg] RON Density (kg/m3) Ethanol-gasoline fuel mixture properties Calculated mixture Reference data (min) Reference data (max) Estimate from simple correlation (PREEM) % Ethanol (vol.) % Ethanol (vol.) Calculated mixture Reference data (min) Reference data (max) Calculated mixture Reference data % Ethanol (vol.) Temperature [K] Gasoline Ethanol Two components considered for preferential evaporation 9

10 ETHANOL/GASOLINE MECHANISM

11 Ethanol-gasoline mechanism C1 to C4 chemistry extensive validated Single fuel components validated against a wide range of experiments, such as flames, shock tubes, flow reactors, Sub models for NOx chemistry and soot formation Detailed mechanism around 480 species, reduced around 250 species

12 Mechanism analysis

13 Sensitivity analysis of a certain reaction R normalized and ranked Reaction r sensitivity with respect to reaction R: Species s sensitivity with respect to species j: R CH ][ O ] k [ 4 2 k AT n e Ea RT Variable Y can be: mass fraction of a target species, or temperature of the gas. 13

14 Flow analysis Atoms fluxes [mol/cm3/sec] H atom O atom Analyses the flow of atoms between species Graphs are drawn for given limits of the flux (low values of limits give very branched praphs). 14

15 Necessity analysis A combination of sensitivity and flow analysis 15

16 Life time analysis Measures the rate of consumption of a species 16

17 Mechanism reduction

18 Reduce the mechanism Use the specific Reduce Mechanism module:

19 Reduce the mechanism Remove redundant species according to: - preset criteria (as the necessity level, calculated within the previous mechanism-analysis step) OR - ad-hoc criteria

20 Options for reduced mechanism You can export your reduced mechanism You can reduce your mechanism in several steps

21 Analyze reduced mechanisms results Compare the results obtained with the original vs. the reduced mechanism User friendly postprocessing interface In this example: the reduced mechanism gives slightly slower ignition compared to the original mechanism, with a difference of only 2%. However, the gain in computational time is approximately 90% for this reduced mechanism case.

22 ETHANOL-GASOLINE DUAL FUEL TABLE GENERATION

23 Table generation process

24 Table generation process

25 Table generation process

26 Table generation process Flame speed DARS-FUEL tabulated chemistry library ECFM-3Z-TKI Laminar flame speed Soot/NOx source terms

27 ECFM-3Z-TKI tables

28 ECFM-3Z-TKI Progress variable solver Pressure: 40 bar, Tunb: 800 K, Z: 6.22e-2, PRF 95

29 ECFM-3Z-TKI Tables Single fuel table (PRF 95) Temperature: 101 points between 600 K and 1600 K Pressure: 8 points between 10 bar and 80 bar Mixture fraction points: 6 points depending on stoichiometry EGR points: 5 values between 0 % and 90 % EGR Temperature segregation: 21 values between 0 and 1 Around 60 MB data Dual fuel table (ethanol-gasoline mixtures) Temperature: 41 points between 600 K and 1600 K Pressure: 11 points between 10 bar and 200 bar Mixture fraction points: 16 points depending on stoichiometry EGR points: 5 values between 0 % and 90 % EGR Temperature segregation: 21 values between 0 and 1 Fuel composition points: 11 values between 0 and 1 (mass fraction ethanol) Around 400 MB data

30 LFS [cm/sec] Laminar Flame Speed Tables Single fuel table (PRF 95) 0.2 Φ 4.0 [-] 300 Autoignition T [K] 1 P 130 [bar] 0 EGR 50 [%] laminar flame speed above 1 cm/s Dual fuel table (ethanol-gasoline mixtures) 0.2 Φ 4.0 [-] 300 Autoignition T [K] 1 P 130 [bar] 0 EGR 50 [%] laminar flame speed above 1 cm/s Ethanol/gasoline fuel fraction Equivalence ratio

31 Soot/NOx tables Single fuel table (PRF 95) Flamelet oxidizer temperature: K in steps of 100 K Logarithmic stepping, bar, 9 points Mixture fraction points: 0-1, 101 points EGR points: 11 values between 0 % and 50 % EGR Scalar dissipation rate points: 0 extinction [1/s] Dual fuel table (ethanol-gasoline mixtures) Flamelet oxidizer temperature: K in steps of 100 K Logarithmic stepping, bar, 9 points Mixture fraction points: 0-1, 101 points EGR points: 11 values between 0 % and 50 % EGR Scalar dissipation rate points: 0 extinction [1/s] Fuel composition points: 11 values between 0 and 1 (mass fraction ethanol)

32 DARS Fuel Accurate reaction schemes ready to use! Plug in to STAR-CD, STAR-CCM+, DARS-TIF No additional work needed Free basic mechanism for TIF/PVM Diesel Gasoline Requires a DARS license Free basic libraries for ECFM Diesel Gasoline Other fuels are available as library on license base Pure components Multicomponent mixture Dual fuel libraries Group Chemistry Reference fuel for Oxygenated methanol, ethanol, propanol Gasoline, Bio fuels Mono aromats Larger aromats toluene, m-xylene a-methylnaphtalene Gasoline, Diesel, Jet Diesel, Jet Linear alkanes n-heptane, n-decane Gasoline, Diesel, Jet Branched alkanes iso-butane, iso-butene, isopentane, iso-octane, iso-dodecane Ester methyldecanoate Biodiesel Additives DME Gasoline Other Emission methane, ethane, propane, butane, pentane, neo-pentane, ethylene, acetylene, propene, hydrogen and others NOx, soot, formaldehyde, unburnt HC and other Gasoline, Diesel, Jet Natural gas, Biomass to gas / liquid, turbines Combinable with all fuels

33 DARS v2.08 Try it today!