An experimental and kinetic study of quadricyclane autoignition at high temperatures

Quadricyclane, with high density and net heat value, can provide more energy to extend the flight distance and enhance the payload capacity of aircraft. The autoignition characteristics of quadricyclane have been investigated behind reflected shock waves in this study. With argon as the diluent gas, experiments are conducted at pressures of 2, 4, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, fuel concentrations of 0.2% and 0.4%, and temperatures ranging from 1276 to 1773 K. The results indicate that the ignition delay time decreases with increasing pressure and fuel concentration, and increases with increasing equivalence ratio, showing a strong positive dependence with the equivalence ratio. Regression analysis of the experimental data has yielded quantitative relationships. To clarify the combustion process, a high-temperature kinetic model based on the NUIGMech1.1 mechanism has been developed, and the validation demonstrates that the model can accurately describe the autoignition characteristics of quadricyclane. Sensitivity and reaction pathways analyses have been conducted, the results reveal that quadricyclane primarily undergoes ring-opening isomerization to produce 2,5-norbornadiene at high temperature. Furthermore, to demonstrate the effect of the strained structure on fuel ignition, the ignition delay times of quadricyclane/air mixture are measured within a temperature range from 952 to 1113 K, pressure of 10 atm, and equivalence ratio of 1.0. When compared with the ignition delay times of JP-10 and Jet A, quadricyclane exhibits the shortest ignition delay time due to its exothermic ring-opening reaction occurring at the initial stage.