  Eulerian-Lagrangian simulations are conducted for two-dimensional Rotating
Detonative Combustion (RDC) fueled by bi-disperse n-heptane sprays without any
fuel pre-vaporization. Parametric studies are performed to study the influences
of droplet diameter and droplet distribution on detonation wave are studied.
The extinction process of the detonation wave is also been analyzed. It is
found that small n-heptane droplets (e.g., 2 um) are completely vaporized in
the fuel refilling area. Increasing the droplet diameter causes the droplet to
fail to evaporate completely within the fuel refilling area and exist after the
detonation wave. A reflected shock can be obsevered after the detonation wave.
When the droplet diameter is larger than 10 {\mu}m, the higher pressure after
the detonation wave leads to the reactants cannot be sprayed into the
combustor, eventually leading to extinction of the detonation wave. In
bi-disperse n-heptane sprays, presence of droplets with small diameter
maintains the stable propagation of the detonation wave. The average
equivalence ratio in the fuel refilling area is lower than total equivalence
ratio (up to 0.66 only), and the average equivalence ratio decreases with the
increase of droplet diameter in bi-disperse n-heptane sprays. The increase in
droplet diameter decreases the detonated fuel fraction and the speed of
detonation wave. The speeds of detonation wave in bi-disperse n-heptane sprays
are 3-9% lower than the respective gaseous cases. Moreover, propulsion
performance of RDC such as thrust and specific impulse decreases with
increasing droplet diameter.
