  Rotating detonation combustion (RDC) fuelled with partially pre-vaporized
n-heptane sprays and gaseous hydrogen is studied with an Eulerian-Lagrangian
method. Our focus is the effects of pre-vaporized n-heptane equivalence ratios
and droplet diameters on detonation wave propagation and droplet dynamics in
two-phase RDC. The results show that when the droplets are small, they are
fully vaporized by the detonation wave. However, when the droplet diameter is
relatively large and/or the detonation wave number is bifurcated, liquid
droplets are observable beyond the refill zone. Moreover, the detonation speed
is considerably influenced by the droplet pre-vaporization and diameter. The
velocity deficits vary between 5% and 30%. Over 70% n-heptane is detonated in
the simulated cases, and there exists a critical droplet diameter (about 20
um), around which the detonated fuel fraction is minimal. Four droplet
trajectories in RDC are identified, which are differentiated by various
evaporation times, residence times and interactions between droplets and the
basic RDC flow structures. Inside the refill zone, three droplet categories are
qualitatively identified. Droplets injected at the right end of the refill zone
directly interact with the deflagration surface and meanwhile have relatively
long residence time. However, droplets injected closer to the travelling
detonation front have insufficient time to be heated and vaporized. Our results
also demonstrate that when pre-vaporization level is low and initial droplet
diameter is large, the liquid fuel droplets may disperse towards the combustor
exit. Furthermore, the droplet dispersion height decreases with liquid fuel
pre-vaporization, while increases with droplet diameter.
