Comparative Study on Ignition Characteristics of 1-Hexene and 2-Hexene behind Reflected Shock Waves

In this work, ignition characteristics of 1-hexene and 2-hexene are investigated behind reflected shock waves. The ignition delay times of 1-hexene and 2-hexene are measured at P = 1.2-10 atm, φ = 0.5-2.0, and T = 1020-1900 K with a fixed fuel concentration of 0.5%. The experimental results show that 2-hexene has shorter ignition delay times and higher reactivity than 1-hexne at high temperature region, and this difference increases with the decrease in equivalence ratio. Kinetic analysis shows that the different reactivity is mainly due to the higher concentration of resonance stabilized C₃H₅-A radical in 1-hexene system. The NUIG and LLNL mechanisms are adopted for simulation. For both 1-hexene and 2-hexene, the NUIG mechanism presents reasonably good predictions under all of the tested conditions. Pathway analysis exhibits that 1-hexene and 2-hexene oxidation is dominated by C-C fission and H-addition reactions, respectively. Sensitivity analysis indicates that 1-hexene ignition is sensitive to small molecular reactions and 2-hexene ignition is mainly sensitive to the reactions associated with the fuel.