Numerical investigation of the liquid-fueled pulse detonation engine for different operating conditions

Abstract

In this study, an intensive simulation platform is developed and implemented to simulate the three stages in the operational cycle of the liquid-fueled pulse detonation engine. The three stages encompass the liquid fuel injection and evaporation process, deflagration-to-detonation transition process, and detonation propagation process. The Lagrangian-Eulerian approaches are employed to model the discrete liquid fuel droplets and the continuous vapor phase, respectively. The breakup and evaporation of liquid droplets are modeled using sub-models, while the interactions between the liquid droplets and the vapor phase are expressed through the two-way interaction models. The Jet-A liquid fuel is injected into the detonation chamber as the fuel for the engine, while the air flow is used as the oxidizer. A reduced chemical kinetic model of fuel/air is used to model the combustion process. The simulation platform is systematically validated against the experimental data for every stage of the operating cycle. To study the influence of the inlet and operating conditions, the numerical simulations are performed for three different operating conditions, which are the change in inlet air temperature, the change in inlet air flow velocity, and the change in liquid fuel mass flow rate. The obtained results indicate that the mass fraction of pre-vaporization of fuel plays an important role in the successful DDT process and/or detonation onset. The deflagration can successfully transit to detonation for both the cases of complete and incomplete vaporization of the liquid droplets inside the detonation chamber. The deflagration cannot successfully transit to detonation for the case of too lean or too rich fuel vapor in the mixture. The calculated burning temperature and Chapman-Jouguet (C-J) detonation velocity are slightly lower in the cases of the incomplete vaporization when compared to the complete vaporization cases. In addition, our numerical results show that the burning process occurs in two stages in the incomplete vaporization case: The first burning stage plays a main role in the successful DDT process, while the second burning stage only plays the role of augmentation.