Numerical study on the mixing and evaporation process of a liquid kerosene jet in a scramjet combustor

Abstract

The mixing and evaporation process of a liquid kerosene jet in a scramjet combustor with dual-cavity is investigated by two-phase Large Eddy Simulation. The gas-droplet flow system is solved through a two-way coupled Eulerian-Lagrangian method. The primary and secondary breakup processes of the liquid fuel jet are taken into account. The Langmuir-Knudsen evaporation model, which considers the non-equilibrium effect, is used to calculate the evaporation process of the droplets. The penetration depth of the jet is in good agreement with the experimental value. The dynamic process of the liquid jet breakup, spray evaporation, and fuel transportation within the combustor are well described by the numerical results. The distribution and evaporation characteristics of the spray are analyzed and most droplets are evaporated within 30 mm downstream of the jet orifice. However, a small portion of droplets with high velocity and low temperature can survive for a long distance. The influence of injection pressure on the mixing process near the cavity is also analyzed, and it is found that the injection pressure affects the total quantity of fuel entrained into the cavity by affecting the fuel distribution in the near-wall region and the total fuel mass flow rate. The local distribution of the liquid and gas phase fuels, local temperature and turbulence characteristics in the cavity are analyzed, and the ignition environment on the development path of the flame kernel is discussed. The results indicate that the injection pressure and the distance between the cavity and the orifice have a critical effect on the quantity of the kerosene entrained into the cavity, which then have a great influence on the ignition environment in the cavity.