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Detonation-based propulsion devices, such as rotating detonation engines (RDEs), must be able to leverage the higher energy densities of liquid fuels in order for them to be utilized in practical contexts. This necessitates a comprehensive understanding of the physical processes and timescales that dictate the shock-induced breakup of liquid drople...
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... schematic of the case initialization is provided in Fig. 1. In both cases, a 100 µm diameter water droplet is initially suspended in ambient air at 1 atm and 300 K. The droplet is also initialized at 300 K, but with a pressure that includes the added Laplace pressure of 2σ/r 0 . Upstream of the droplet, the inflow boundary uniformly supplies air at the analytic post-shock state (p ps , T ps , ...
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... diameter drops more quickly in the M s = 2 case. This indicates faster formation of small secondary droplets, which may be due to the more pronounced ligament formation in the droplet wake (see τ = 0.386 in Figs. 2-3). However, after τ ∼ 1.3, the mean droplet diameter is consistently lower in the M s = 3 case. The reason for this can be seen in Fig. 10, which shows the total liquid mass in droplets of varying sizes through time. As with the PDFs in Fig. 7, the droplet diameters are grouped into 40 logarithmically-spaced bins, and the total mass of all droplets within each bin are computed at each time. Despite the rapid initial formation of small secondary droplets, which causes the ...
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... droplets is critical for liquid-fueled detonations, as their stable propagation requires a sufficient quantity of small fuel droplets that can evaporate and react with the surrounding oxidizer prior to the wave-relative sonic plane. The necessary droplet diameters for this to occur have been estimated as 5-7.5 µm [61]. Following this metric, Fig. 11 shows the fraction of total liquid mass within droplets less than 5 µm in diameter over time. This fraction can be interpreted as the degree of atomization of the primary ...
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... be distinguished from the background gas. While the results indicate that the primary droplets have largely broken up by τ ∼ 2, Figs. 2 and 3 show that the cloud of secondary droplets can still appear as a cohesive structure when viewed from the side. As such, the shorter breakup times reported here may be due to the definition presented in Fig. 11, which is inaccessible with current experimental diagnostics. The discrepancies could also be partly due to the assumption of quasi-instantaneous thermomechanical equilibrium discussed in the introduction. Finite rate equilibration that takes place over several simulation time steps could lead to a slower deposition of momentum and ...
