Experimental Investigation on Combustion Characteristics of Aviation Kerosene Under Sub/Supercritical Conditions

Considering the turbine inlet temperature of the advanced aeroengines grows higher and higher, the cooling capacity of the onboard aviation kerosene has to be fully used. Consequently, the kerosene may experience the transition from subcritical to supercritical before injected into the combustion chamber. The fluid properties vary greatly in the phase change process, which significantly changes the combustion process of kerosene in the combustion chamber. In this study, the swirling flame of subcritical and supercritical kerosene was experimentally investigated within a model combustion chamber (T_fuel = 310K–713 K). The flame morphology, the fuel-lean blowout boundaries, and the stability of flame were obtained using flame luminosity signals and CH* signals. And the Dynamic Mode Decomposition (DMD) was used to study the transient changes of the flame. The results present that the flame morphology exhibits differences as the fuel–air ratio (FAR) changes. The fuel-lean blowout FAR is increased by the flash boiling. Compared to the subcritical state, the lean blowout FAR of supercritical kerosene is considerably lower. Besides, the combustion oscillation mode of the subcritical kerosene flames is characterized by “low-frequency, high-amplitude.” Regarding the supercritical kerosene flames, the combustion oscillation mode is “high-frequency, low-amplitude.” The oscillation behavior of the flame is highly related to the structure of the flow field. As the kerosene gets closer to the supercritical state, this effect becomes more pronounced.