Comparative Shock Tube and Kinetic Study on High-Temperature Ignition of 2,3-Dihydrofuran and 2,5-Dihydrofuran

The ignition delay times of 2,3-dihydrofuran (23DHF) and 2,5-dihydrofuran (25DHF) were investigated over the temperature range of 1100 to 1635 K with pressure of 1.2, 4, and 10 atm for lean (φ= 0.5), stoichiometric, and rich (φ= 2) fuel/O₂/Ar mixtures. 23DHF shows shorter ignition delay times than 25DHF under the above conditions. A modified model (M_Tran model) was presented to improve the prediction of DHF ignition. Kinetic analysis indicated that most 23DHF transforms to cyclopropane carboxaldehyde (CPCA) and further to croton aldehyde (CA) by isomerization while most 25DHF dehydrogenates to furan. Some reactions involving CA and propene show strong sensitivity for 23DHF ignition. Some reactions of furan present strong effect on 25DHF ignition. Ignition delay data between furan, 23DHF, and 25DHF were compared to reveal the effect of number and location of carbon double bonds on the ignition characteristics. The bond dissociation energies of DHF are not as strong as that of furan and are significantly influenced by the locations of carbon double bonds, causing the differences in structure stability. As a result, the ignition trends of furan and DHF in this research are furan < 25DHF < 23DHF.