Laminar flame speeds for n-butanol/air mixtures at elevated pressures and temperatures: An experimental and numerical study

Laminar flame speeds of n-butanol/air premixed flames were measured experimentally and numerically at elevated pressures and temperatures for a wide range of equivalence ratios. Laminar flame speeds were obtained experimentally from the temporal evaluation of the flame front of spherically outwardly propagating flames at zero stress rate. The shadowgraph technique was employed to gain optical access to the constant volume combustion chamber. Flame propagation images were captured by a high-speed camera and MATLAB codes were used to process the images and calculate laminar flame speeds. Flame speeds have been calculated numerically using CHEMKIN-Pro based on a short reaction mechanism for n-butanol oxidation, which was derived from a previously published full reaction mechanism. Numerical predictions were in qualitative agreement with experimental data. The effects of initial pressure and temperature elevation were analyzed. Also, the effect of simultaneous elevation of initial pressures and temperatures is documented. For all experimental conditions, the maximum flame speed was found at around equivalence ratio 1.1. In general, flame speeds decreased with the elevation of initial pressure and increased with initial temperature elevation.