Shock interactions and re-initiation mechanism of liquid ethanol-fueled rotating detonation wave

Abstract

We present a numerical simulation of a two-phase rotating detonation fueled by liquid ethanol and pre-heated air in a two-dimensional rotating detonation combustor. The study aims to understand the structure and shock interactions of the two-phase rotating detonation wave (RDW) using a two-way coupled Eulerian–Lagrangian framework. Initially, the flow field is ignited with a gaseous rotating detonation, followed by the injection of liquid ethanol and pre-heated air at near-stoichiometric and fuel-lean conditions. Observations reveal incomplete evaporation of the newly injected liquid droplets, which affects the propagation of the initial gaseous RDW and leads to its decoupling. Subsequently, a two-phase RDW is re-initiated. Different types of shock waves are identified in the unsteady flow field, and their interactions and contribution to the re-initiation of the rotating detonation are discussed. An analysis of the established two-phase rotating detonation elucidates mechanisms underlying droplet evaporation and RDW propagation, highlighting the roles of incident shocks, transverse waves, and Mach stems. Additionally, we investigate the two-phase RDW under the fuel-lean condition, where the excessive presence of air mixing with unburned ethanol vapor can cause pre-ignition, leading to a chaotic rotating detonation field. The existence of reversed shock waves and ongoing collisions with the RDW can gradually reduce its intensity, induce fluctuations in the propagation velocity of the two-phase RDW, and ultimately lead to quenching.