Structure and Dynamics of 2D and 3D Detonations in Ethylene-Air Mixtures

Recent years have seen an increasing interest in using ethylene as an alternate fuel to heavy hydrocarbons for detonative propulsion due to its better detonability. In this work, we present a brief summary of recent effort to perform the first systematic numerical exploration of the properties of detonations in ethylene-air mixtures across a wide range of conditions (pressures, equivalence ratios, fuel preheat) in 2D and 3D geometries using complex multi-step chemical kinetics and high-fidelity numerical simulations. In particular, we study the properties of these detonations as a function of the equivalence ratio to determine lean detonability limits. We also study the propagation limits of 2D detonations in channels of varying width. Overall, we observe that cells are highly irregular, and smaller than the expected experimental cell size. Hierarchy of cell sizes is observed due to frequent failure/re-ignition events resulting in the periodic formation of transverse detonations. These events lead to a complex detonation structure with various flow features that are typical in unstable detonation mixtures. Finally, we conclude by presenting a comparison between 2D and 3D ethylene/air detonations at similar conditions in rectangular channels in the presence of wall loss effects.