  Spray detonation in n-heptane two-phase mixtures is simulated using Eulerian
Lagrangian method. Two-dimensional configuration is considered, and the effects
of droplet diameter and liquid equivalence ratio on detonation propagation,
structure, and dynamics are investigated. The results show that the average
detonation propagation speed first increases and then decreases as liquid
equivalence ratio changes, and the speed peaks at higher liquid equivalence
ratio for larger droplets. The triple points and transverse detonations
vaporize or aerodynamically expel the droplets from their trajectories,
resulting in non-uniform distributions of fuel vapor and reaction zones behind
the detonation. In addition, droplet dispersion distance in the post-detonation
area increases for larger droplets due to lower evaporation. Moreover, small
droplets generally lead to higher detonated n-heptane fraction, and fuel
detonative combustion directly affects the variations of detonated fuel
fraction. For larger droplets, V shaped dependence on liquid equivalence ratio
is seen for large droplets, dominated by variations of post-detonation
deflagration. It is found that spray detonation structure is significantly
influenced by liquid fuel equivalence ratio and droplet diameter. The
dependence of key locations in spray detonation structure on liquid fuel
properties is also evaluated, e.g., reaction front and sonic plane.
Furthermore, the leading shock Mach number slightly decreases with droplet
size. When the liquid equivalence ratio is high, spray detonation exhibits
pronounced unsteadiness, such as instantaneous or complete extinction. Either
extinction is caused by strong heat absorption of evaporating droplets behind
the shock. Moreover, localized detonative spot is observed due to the
compression of multiple transverse shocks.
