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Published byYadiel Kimball Modified about 1 year ago

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Non-premixed turbulent combustion (Flamelet Progress Variable Approach (FPVA))

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Flamelet-based combustion model for compressible flows

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Source term is highly non-linear The source term: with

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Model algorithm Transported variables NSE Turbulence Combustion Tabulated chemistry Table lookup Pre-computed chemistry Temperature Newton iteration Not looked up from table All other quantities Chemistry does not account for compressibility effects and viscous heating EOS Mixing rules

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Flamelet models for non-premixed combustion The species mass fractions are related to the mixture fraction Z by the solution of the steady flamelet equations, parameterized by the scalar dissipation rate. The basic assumption is that the chemical time-scales are short enough so that reactions occur in a thin layer around stoichiometric mixture on a scale smaller than the small scales of the turbulence. Physically, the flame structure is locally one-dimensional and depends only on time and on the coordinate normal to the flame front (or on z). This has two consequences: the structure of the reaction zone remains laminar, and diffusive transport occurs essentially in the direction normal to the surface of stoichiometric mixture. Then, the scalar transport equations can be transformed to a system where the mixture fraction is an independent coordinate. A subsequent asymptotic approximation leads to the flamelet equations.

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Compute flamelet equations and create chemistry table from the solutions Step 1: Inputs : batesgn.therm (thermodata) batesgn.trans (transportdata) batesgn.mech (reactions) 1) CreateBinFile batesgn.therm batesgn.trans thermo.bin 2) ScanMan thermo.bin batesgn.mech batesgn.pre 3) FlameMaster batesgn.pre.in (input file with start profile) Flamelet solution Step 2: Goal : Create chemistry table Introducing the assumption of a beta- function sub-filter distribution of the mixture fraction leads to CreateChemTable Mum/bin/CreateChemTable Input : CreateChemTable.in thermo.bin Flameletlist.txt Output : table (binary file)

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Jet in crossflow for combustion 9 species 28 reactions : N2 H O2 O OH H2 H2O HO2 H2O2 Global reaction : H2 + ½ (02 + 3.76N2) H20 + ½(3.76N2) fuel + air

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