Laminar flame speeds and flame instabilities of pentanol isomer-air mixtures at elevated temperatures and pressures

Laminar flame speeds of three pentanol isomer (1-, 2-, and 3-pentanol)-air mixtures were measured at equivalence ratios of 0.6-1.8, initial pressures of 0.10-0.75 MPa, and initial temperatures of 393-473 K using the outwardly propagating spherical flame. A recently developed kinetic mechanism of 1-pentanol oxidation (Dagaut model) was used to simulate the laminar flame speeds of 1-pentanol-air mixtures under experimental conditions. A comparison between simulation and measurement shows that the simulation yields good agreement on the stoichiometric and fuel-rich side, but it gives lower values on the fuel-lean side. A kinetic modeling study was performed, and several rate constants of selected elemental reactions were modified on the basis of the sensitivity analysis. The modified model gives good prediction on the laminar flame speed under all experimental conditions. The modified model is also validated against the jet-stirred reactor (JSR) experimental data, and it exhibits good prediction for most species. 1-Pentanol gives the fastest laminar flame speed, followed by 3- and 2-pentanol. 2- and 3-pentanol have very close values considering the experimental uncertainty. With the increase of the pressure, the difference in the laminar flame speed among pentanol isomers is decreased. The flame instability of three pentanol isomers was also analyzed. 2- and 3-pentanol have similar instability behavior with a close density ratio, flame thickness, and Lewis number, while 1-pentanol shows slightly high instability behavior. In comparison to 2- and 3-pentanol, 1-pentanol has a smaller critical radius and Peclect number, and this suggests its high instability behavior.