Supersonic turbulent combustion characteristics of a rocket-based combined-cycle engine combustor

This paper reports on combustion characteristics of a Rocket-Based Combined-Cycle (RBCC) engine operating at ramjet/scramjet transition mode numerically. Three-dimensional Large Eddy Simulation (LES) with liquid kerosene (C₁₂H₂₃) sprayed and vaporized is used to study the inherently unsteadiness of such a propulsion system. Results of pressure oscillation amplitude and frequency in the combustor, as well as pressure distribution along the flow-path wall are validated by experimental data, all show good agreement. Coupling with reduced chemical kinetics of kerosene and hydrogen, LES result is compared with Reynolds-Averaged Navier-Stokes (RANS) simulation, and shows significant unsteady features. Supersonic flow and turbulent flame structures are further analyzed by density gradient magnitude, vortices development and combustion parameter distributions. The combustor is divided into different regions recognized by non-uniform characteristics. Results show that the unsteady primary rocket jet, which is designed rich in fuel and over expanded, has significant effects on the vaporization features of kerosene injected from the fuel struts, and consequently on the unsteady combustion characteristics of the engine combustor.