Structure and Dynamics of Three Dimensional Spray Detonations in Jet Fuels

Recent years have seen a surge in numerical studies of spray detonations due to their relevance in hypersonic propulsion devices and energy conversion systems. Having said that, all such prior studies are currently limited to two-dimensional (2D) channels with ideal boundary conditions. In this work, for the first time, we carry out three dimensional (3D) numerical simulations of detonations propagating in a liquid jet fuel spray. In particular, the simulations are carried out in dodecane/air mixtures using an Eulerian-Lagrangian formulation with complex chemistry, complete molecular transport, realistic boundary conditions and state-of-the art spray sub-models for droplet drag, atomization and evaporation. The obtained detonation properties are then contrasted with those of purely gaseous detonations. A sensitivity study is conducted by varying the droplet break-up time in the droplet atomization model. The results show that in case of fast atomization, the detonation cells are slightly irregular but are qualitatively and quantitatively similar to those of purely gaseous detonations. However, when the atomization is slow, the cells become more regular in shape but smaller in size when compared to the purely gaseous case. Overall, these results demonstrate that detonation properties of jet fuels in 3D geometries are both qualitatively and quantitatively different from those obtained from 2D geometries.