Abstract
Successful ignition process is the prerequisite for achieving stable combustion in a scramjet combustor coupled with a cavity. A single pulse laser is adopted to ignite the fuel/air mixture that is generated by a sonic ethylene jet injection into heated Mach 2.92 crossflows. In order to reveal the complicated combustion regime, large eddy simulations are performed to reproduce the unsteady reactive process observed in the experiments, from an initial ignition kernel to the cavity-stabilized flame. From qualitative comparisons, the predicted results show reasonably good agreement with experimental observations. After ignition, the flow dynamics drive the flame kernel to the leading edge of the cavity. Herein, a flame base is established, and provides hot intermediate products and high temperature to continually ignite the fresh combustible mixture downstream. Finally, a partially-premixed flame is stabilized in the cavity. Due to a shorter flow residence time, the intensity of chemical reactions becomes weak in the downstream region of cavity. In comparison with no-reactive flows, the chemical heat released during the reactions induces high temperature, and the jet wakes penetrate a deep height into the mainstream. A thorough understanding of unsteady flame regime is propitious to instruct the design and optimization of combustor.
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