Numerical Study on a Cycle of Liquid Pulse Detonation Engines

A typical cycle of a liquid pulse detonation engine (PDE) often involves three main processes, which are injection and evaporation process, deflagration-to-detonation transition process (DDT), and detonation propagation process. These three processes often include a number of complex subprocesses, which strongly influence the performance characteristics of the engine. Thus, it is important to understand the physical and chemical insights of these processes in an operating cycle of the liquid PDE to improve the engine performance characteristics. In this study, numerical simulations are performed to simulate for the complete operating cycle of the liquid PDE. The numerical method is developed based on the Eulerian–Lagrangian approaches. Particularly, the continuous vapour phase is described using Navier–Stokes equations in the Eulerian frame of reference, while the liquid fuel droplets are modelled using discrete phase model in the Lagrangian frame of reference. The liquid fuel is injected into the detonation chamber through a cone nozzle injector model. The evaporation process of the liquid droplet is modelled using the D-square law. The density-based solver with a shock-capturing scheme is employed to simulate for both the DDT and detonation propagation processes. The combustion process is modelled through the reduced chemical kinetic model of Jet-A fuel. The obtained numerical results are in good agreement with both the experimental and numerical data. Both physical and chemical insights of the operating cycle are investigated. The obtained results show that the evaporation process and mixing process play a key role in the homogeneity of the fuel/air vapour mixture. The deflagration wave can successfully transit to detonation wave for a certain range of injected fuel mass flow rate. The DDT length strongly depends on the temperature of incoming airflow as well as liquid fuel mass flow rate.