An investigation on fuel similarity of turbulent flames for C₄-C₈ n-alkanes

In this study we experimentally investigated the propagation speed of constant-pressure expanding flames in near-isotropic turbulence using a dual-chamber, fan-stirred vessel. The motivation of the work is to test whether the concept of fuel similarity for C₄-C₈ n-alkanes on laminar flames also holds for turbulent flames. Previously it was found that the laminar flame speed, laminar flame thickness and Markstein length are almost identical for these fuels. If this fuel similarity concept can also be shown for turbulent flames, it will suggest a canonical flame structure for large hydrocarbon fuels of the same chemical family, i.e., large fuels always decompose to small C₀-C₄ fuel fragments before being oxidized, and would significantly simplify/generalize the description of such flames. Our preliminary results show that in the flamelet and thin-reaction zone, the turbulent flame speeds of these fuels indeed assume similar values at various pressures, equivalence ratios and turbulence intensities, thereby extending the concept of their fuel similarity to turbulent flame propagation, within the present parametric range of investigation.