Eulerian-Lagrangian LES analysis of residence time in a scramjet cavity combustor*

One of the principal considerations in the design of scramjet combustors is the residence time associated with the flame stabilization mechanism. This residence time must be long enough to allow for mixing and combustion processes to occur. A traditional approach for numerical evaluation of this quantity involves the injection of a passive scalar into the cavity and subsequent measurements of the decay in its concentration, yielding only a single mean value of the residence time. This work presents a one-way coupled Eulerian-Lagrangian approach in which passive tracer particles are injected into the flow. This enables continuous measurement of residence time with spatially and temporally varying statistics as well as improved analysis of mixing without disturbing the Eulerian field. This approach is applied to large-eddy simulations of a cavity-stabilized scramjet combustor in both non-ignited and ignited states, the effects of combustion on the flow field are evaluated, and implications on combustor design are discussed.