Unstretched laminar flame speed and unburned Markstein length of n-decane and iso-octane blends

Blends of n-decane and iso-octane are employed as surrogates for Fischer-Tropsch-derived Sustainable Aviation Fuels (SAFs), and the unstretched laminar flame speed and unburned Markstein length of such premixed and pre-vaporized surrogates are studied experimentally and numerically in the present study. The experiments are performed using a jet-wall stagnation burner and Particle Image Velocimetry. For the numerical simulations, either the detailed and skeletal or the reduced, merged, and validated chemical mechanisms of n-decane and iso-octane are used. It is reported that the measured laminar flame speed decreases linearly with increasing the iso-octane volumetric fraction, which agrees with the predictions of the developed merged mechanism. A second-order correlation that models the effects of both iso-octane volumetric fraction and the fuel–air equivalence ratio on the unstretched laminar flame speed is proposed and shown to yield results in agreement with those of the measurements. It is shown that changing both the fuel–air equivalence ratio and the iso-octane volume fraction changes the effective Lewis number, which ultimately influences the unburned Markstein length linearly. The present study provides new experimental data and empirical correlations of the unstretched laminar flame speed and unburned Markstein length for n-decane and iso-octane blends, and a reduced, merged, and validated combustion chemistry mechanism of these blends.