For more complex fuel mixtures, high levels of EGR, or pressures and temperatures that may be outside of the available experimental range, the Table Library option allows more general accounting of flame-speed dependencies.

With increasing fuel variability, the effects of fuel composition on flame speeds need to be captured accurately. Gasoline, for example, consists of hundreds of components; representing the behavior of gasoline may require 3–8 components. Ansys Forte comes installed with pre-built laminar flame-speed tables for 64 surrogate fuels as part of the Table Library option. The fuels covered in the Table Library option represent several classes: families of n-alkanes, iso-alkanes, cyclo-alkanes, alkenes, cyclo-alkene, iso-alkene, aromatics, ethers, cyclo-ethers, alcohols, and methyl esters. The fuels are listed in Table 1: Fuels for which prebuilt laminar flame speeds are available as part of the Table Library option.

In addition to fuel effects, the operating conditions of equivalence ratio, temperature, pressure, and EGR affect flame speeds. With wider operating regimes, including fuel stratification and boosted conditions, it is difficult to predict the correct trends of flame speeds using correlations. For the 64 surrogate fuels that are part of the Table Library option, flame speeds have been calculated over a wide range of operating conditions. The Ansys Forte laminar flame-speed tables were generated using the Ansys Chemkin [5] Flame-speed Table Generator. This Chemkin option uses an adiabatic, premixed, laminar flame-speed calculator to determine the flame speeds over a range of conditions for a particular fuel component, employing detailed (high-temperature) kinetics for the fuel-combustion.

The conditions that can be varied include: fuel-air equivalence ratio, initial temperature of the unburned gas, pressure, and dilution rate (for simulated EGR). For the pre-built flame speed tables available as part of the Table Library option, the conditions covered for the built-in tables are summarized in Table 2: Mixture conditions covered by the built-in laminar flame-speed tables available in the Table Library option.

When conditions are encountered outside of the range described in Table 2: Mixture conditions covered by the built-in laminar flame-speed tables available in the Table Library option, the flame speed is determined by sampling points within the table, and creating a linear-least-square fit of a power law / Gulder equation that can be used to extrapolate to the given conditions.

Using pure-fuel flame speeds and local fuel composition in the CFD simulation, multicomponent-fuel flame speeds are calculated on-the-fly using non-linear blending of the single-component values [26]. This Table Library option provides: