Effects of droplet breakup models in simulating liquid-fueled rotating detonation engines

Recent interest in liquid-fueled rotating detonation engines (RDEs) has highlighted the need to understand how liquid droplets interact with the detonation wave. To investigate this, we have employed in our numerical simulations an Eulerian-Lagrangian framework with detailed particle modeling¹ including droplet deformation, breakup, and evaporation. A premixed mixture of pure oxygen and n-dodecane in both liquid and prevaporized form was injected uniformly into a three-dimensional unrolled configuration of an RDE. Three different droplet diameters of sizes 5 μm, 15 μm and 30 μm were studied, while the effects of droplet breakup were addressed using an empirical Weber number-based model (WERT) and a model that drives droplet breakup through the growth of hydrodynamic instabilities - Kelvin-Helmholtz Rayleigh-Taylor (KHRT). The multiphase simulations showed a weaker detonation wave due to inhomogeneities in the fuel droplet distribution, and drag-induced fuel oxidizer segregation in the refill region. We also found the detonation velocity decreased with an increase in droplet diameter, attributed to slower vaporization of larger diameter droplets, reducing the local energy released near the wave front. The WERT model predicted breakup in the refill region, resulting in smaller droplets, in contrast to the KHRT model, where the initial droplet size was maintained throughout the refill region. These smaller droplets evaporate and burn rapidly, yielding a higher detonation velocity and thrust compared to the KHRT model.

¹B. J. Musick et al., Combust. Flame, Suppl. vol. 257 (2023)