Resolving Supercritical Effects in Multiphase Detonation
Abstract
The main goal of this research is to enhance the fundamental understanding of breakup, evaporation, and reaction of liquid fuel droplets under supercritical conditions and elucidate their impact on multiphase detonation. The next generation of detonation engines relies on liquid fuels due to their high energy content and storability. However, the multiphase nature of detonation, especially during the transition from subcritical to supercritical conditions (i.e., transcritical), which alters fuel breakup, evaporation, and fuel-air mixing, remains elusive. The main objectives of this proposal are to (1) elucidate the mechanisms of breakup, evaporation, and reaction of a transcritical droplet interacting with a detonation wave from molecular level to higher scales; (2) determine the effects of transcritical droplet behavior on multiphase detonation mechanisms when several fuel droplets interact with a detonation wave. We will test the hypothesis that transitioning to a supercritical state accelerates droplet breakup and evaporation, positioning fuel vapor closer to the detonation front, enhancing the detonation wave speeds. Capturing supercritical behavior is very challenging experimentally as supercritical diffusion can be mistaken for motion-induced blurring when a cloud of vapor surrounds high-speed droplets. Classical models overlook critical changes in fluid properties near the mixture critical point, leading to a shift in droplet breakup modes and dominance of the supercritical gas-like diffusion regime. This leads to inaccurate prediction of post-breakup droplet size and evaporation rate essential to control fuel-air mixing and reaction rates for initiating and sustaining detonationwaves. To address this critical challenge, a multiscale computational paradigm is proposed to (1) capture the molecular-level interfacial behavior governing the transition to the supercritical regime and surface tension changes using Molecular Dynamics (MD) simulations; (2) develop subgrid-scale closure models from MD-driven data to link the nanoscale interfacial dynamics to Direct Numerical Simulation (DNS). This coupled model will elucidate the underlying mechanisms behind breakup, supercritical phase change, and reaction of a microscale single droplet interacting with a detonation wave. Finally, (3) mesoscale Eulerian-Lagrangian (EL) simulations will elucidate the impact of supercritical droplet behavior during the interaction of a cloud of droplets with a detonation wave. Thisapproach ensures supercritical effects are captured from molecular-level interfacial dynamics to droplet-detonation wave interaction in larger scales. The merit of this work lies in developing a coupled MD-DNS framework validated with experimental measurements under reacting/non-reacting conditions in Sandia National Labs# high-pressure vessels and Texas A&M multiphase detonation tube. A novel comprehensive droplet breakup and evaporation model capturing sub- to supercritical transitionwill be developed and integrated with existing multiphase flow (EL) models. This is essential for propelling the progress of detonation spray models developed at the U.S. Naval Research Laboratory (NRL). Achieving the goal of this project and collaboration with NRL scientists will directly contribute to the advancement of liquid-fueled detonation engines that hinge upon an understanding of droplet behavior to control fuel-air mixing under detonation conditions to establish and sustain the detonation. This knowledge is critical for developing smaller, lighter, and more efficient high-speed prolusion engines such as rotating detonation engines, scramjets, and rockets to meet the rigorous demands of sea-based aviation operations of the Navy and Marine Corps. This project will contribute to future naval research workforce development by training students in areas vital to national security. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 12, 2025
- Source ID
- N000142512191
Entities
People
- Dorrin Jarrahbashi
Organizations
- Office of Naval Research
- Texas Engineering Experiment Station
- United States Navy