Study on Combustion Oscillation Characteristics in a Kerosene-Fueled Supersonic Combustor

This paper investigates the combustion oscillation characteristics of kerosene fuel under varying equivalence ratios in a supersonic combustor, operating with an inflow Mach number of 3, a stagnation temperature of 1920 K, and a stagnation pressure of 2.9 MPa. The findings reveal that as the equivalence ratio increases, the oscillation amplitude decreases. Two distinct flame stabilization modes were identified during the oscillation process: cavity recirculation-stabilized combustion and shear-layer-stabilized combustion. At higher equivalence ratios, combustion oscillations are mitigated, and overall flame intensity diminishes, particularly in the shear-layer-stabilized mode. The spectral analysis of pressure oscillations identified three primary frequency ranges: 2.7–100 Hz, attributed to unstable fuel supply; 152 Hz, associated with flame flashback and blow-off; and 700–1000 Hz, linked to flow separation. Additionally, detailed schlieren and oil mist visualizations were used to capture the dynamic changes during the flame flashback process. A one-dimensional thermodynamic analysis further revealed the presence of a thermodynamic throat within the combustor, with thermal choking at the combustor identified as the main cause of flame flashback. The experimental phenomena, combined with theoretical analysis, show that appropriately increasing the equivalent ratio can maintain the shear-layer-stabilized combustion.