General correlations of iso-octane turbulent burning velocities relevant to spark ignition engines

A better understanding of turbulent premixed flame propagation is the key for improving the efficiency of fuel consumption and reducing the emissions of spark ignition gasoline engines. In this study, we measure turbulent burning velocities (S_T) of pre-vaporized iso-octane/air mixtures over wide ranges of the equivalence ratio (φ = 0.9–1.25, Le ≈ 2.94–0.93), the root-mean-square (r.m.s.) turbulent fluctuating velocity (u⁰= 0–4.2 m/s), pressure p = 1–5 atm at T = 358 K and p = 0.5–3 atm at T = 373 K, where Le is the effective Lewis number. Results show that at any fixed p, T and u⁰, Le < 1 flames propagate faster than Le > 1 flames, of which the normalized iso-octane S_T/S_Ldata versus u⁰/S_Lare very scattering, where S_Lis the laminar burning velocity. But when the effect of Le is properly considered in some scaling parameters used in previous correlations, these large scattering iso-octane S_T/S_Ldata can be collapsed onto single curves by several modified general correlations, regardless of different φ, Le, T, p, and u⁰, showing self-similar propagation of turbulent spherical flames. The uncertainty analysis of these modified general correlations is also discussed.