Droplet Dynamics Characterization in Spray Detonations of Hydrocarbon Fuels*

Detonations have long held promise of significant efficiency gains in propulsion and energy conversion devices. Despite significant progress over the years in studies of gas-phase detonations, liquid-fuel detonations remain largely unexplored. Presence of a liquid spray brings in a multitude of complexities such as droplet-flow and droplet-droplet interactions, spray atomization, evaporation, and mixing, which all pose significant challenges for modelling. Here, we present results of the spray detonation simulations in dodecane/air mixtures using an Eulerian-Lagrangian formulation with complex chemistry and detailed multi-species transport. We contrast the obtained detonation properties with those of a purely gas-phase detonation. Furthermore, we discuss the flow regimes encountered by the liquid spray in a freely propagating detonation in order to determine the fidelity and limitations of the existing droplet drag, atomization, and evaporation models. In particular, we analyze the thermodynamic conditions encountered by liquid droplets along with droplet Reynolds, Mach, Weber, and Ohnesorge numbers. We conclude by discussing future extensions of the physical models necessary for the accurate and predictive modelling of liquid spray detonations.