Simulations of rotating detonation combustion with in-situ evaporating bi-disperse n-heptane sprays

Abstract

Eulerian-Lagrangian simulations are conducted for two-dimensional Rotating Detonative Combustion 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 the rotating detonation wave. The extinction process of the detonation wave is also been analyzed. It is found that small n-heptane droplets (e.g., 2 µm) 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 observed after the detonation wave. When the droplet diameter is larger than 10 μm, 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 stabilizes the detonation wave. The average equivalence ratio (up to 0.66 only) in the fuel refilling area is lower than total equivalence ratio (1.0 in this work), and the average equivalence ratio decreases with increased droplet diameter in the bi-disperse n-heptane sprays. The increase in droplet diameter decreases the detonated fuel fraction and detonation wave speed. The detonation speeds in bi-disperse n-heptane sprays are 3–9% lower than the respective gaseous cases. Moreover, the results also show that propulsion performance of rotating detonation combustor, such as thrust and specific impulse, decreases with the droplet diameter.