The Flamelet Generated Manifold (FGM) model requires a reaction progress variable which is usually defined as a weighted sum of species mass fractions. This progress variable should increase monotonically as flamelet states progress from unburnt to chemical equilibrium. A favorable attribute of the progress variable is that the flamelet species should change gradually with the progress variable, which reduces sensitivity of these species to any predicted errors in the progress variable. Previous publications have presented optimization algorithms for specific flamelet operating conditions, including fuel and oxidizer compositions and temperatures, and pressures. This work applies the HEEDS optimization software to find optimal species weights for a range of fuels and operating conditions. The fuels included are methane, methane-hydrogen, n-dodecane and n-heptane, at fuel-oxidizer temperatures of 293K and 1000K, and pressures of 1 and 30 atmospheres. For manifolds modeled by constant pressure ignition reactors, the optimal progress variable weights using four species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.52, αH2 = 1}, and for eight species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.51, αH2 = 1, αC2H2 = 0.16, αOH = −0.66, αH = −0.38, αO = 0.4}.

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