On the distributions of fuel droplets and in situ vapor in rotating detonation combustion with prevaporized n-heptane sprays

Abstract

Rotating detonation combustion fueled with partially prevaporized n-heptane sprays is studied with the Eulerian–Lagrangian method. A flattened two-dimensional domain with periodic boundaries is considered to mimic the annular rotating detonation combustor. This work focuses on the effects of prevaporized gas temperature and equivalence ratio on two-phase rotating detonation wave propagation and n-heptane droplet vaporization characteristics in the refill zone. The results show that gas temperature has a great impact on n-heptane sprays vaporization in the refill zone. The droplet evaporation rate increases with the gas temperature, especially when they are close to the deflagration surface. High evaporation rate can be observed for those droplets that are freshly injected into the chamber because they closely interact with the hot product gas from the previous cycle of the rotating detonation. A vapor layer between the droplet-laden area and deflagration surface exists and high concentrations of n-heptane can be found along the deflagration surface. A conceptual model for the droplet and vapor distribution in the refill zone is proposed. The results also show that the blast waves can encroach the refill zone and therefore influence the droplet thermodynamic properties inside the refill zone. The blast waves influence the droplet evaporation rate but have limited effects on droplet temperature, diameter, and spatial distributions. Also, the detonation propagation speed increases with increased prevaporized gas temperature and/or equivalence ratio. The detonation cell size decreases and becomes more uniform as the reactant temperature increases. Moreover, the size and irregularity of rotating detonation cells increase when the prevaporized gas equivalence ratio decreases.