Shock Tube Study on Propanal Ignition and the Comparison to Propane, n-Propanol, and i-Propanol

High temperature ignition characteristics of propanal/oxygen mixtures diluted with argon were studied in a shock tube for temperatures ranging from 1050 to 1800 K, pressures ranging from 1.2 to 16.0 atm, fuel concentrations of 0.5, 1.25, 2.0%, and equivalence ratios of 0.5, 1.0, and 2.0. A detailed kinetic model consisting of 250 species and 1479 reactions was developed and validated against experimental results. To clarify the influence of functional groups and their positions on the oxidation, previously measured ignition delay times of propane, n-propanol, and i-propanol were employed for comparison. It was found that ignition delays are in the order of propane > i-propanol > n-propanol > propanal. Reaction pathway analysis indicated that the intermediate species of propane and i-propanol are rather stable, while the products of n-propanol and propanal are more reactive, which leads to the decreased ignition delay times. Sensitivity analysis demonstrated that some fuel-specific reactions exhibit relatively large sensitivity during the ignition of the four C₃ fuels.