(608c) The Low-Temperature Oxidation of Diethyl Ether with Non-Boltzmann Reactions of Hot Radicals

Several properties of diethyl ether make it an appealing transportation fuel, particularly in low-temperature compression ignition engines. Low-temperature combustion, characterized by sequential additions of O₂ to fuel radicals and subsequent isomerizations, enables rovibrationally excited radicals to react prior to stabilization into Boltzmann distributions. The effects of these “non-Boltzmann” reactions on the low-temperature oxidation of diethyl ether are unknown. Electronic structure calculations and transition state theory are used to compute rate constants for the low-temperature oxidation of diethyl ether. Rate constants that take into account the fraction of rovibrationally excited radicals that react with O₂ prior to thermalization are also computed, resulting in a new chemical kinetic mechanism. Ignition delay curves are computed using two mechanisms: one that contains only thermal reactions, and a second augmented by non-Boltzmann reactions. Simulations suggest that non-Boltzmann reactions will decrease the predicted ignition delay by a sizeable factor. As the pressure increases, the effective contribution of these reactions diminishes. These results suggest that non-Boltzmann phenomena can have a significant effect on real-world applications.