Flame dynamic characteristics of evaporative flameholder for air turbo rocket engine based on guided gas and pilot kerosene

To investigate the flame dynamic characteristics of an evaporative flameholder in the combustion chamber of an Air Turbo Rocket (ATR) engine under the combined effects of guided ethylene and duty kerosene, a model evaporative flameholder was used as the experiment object. Combustion experiments were conducted at room temperature and atmospheric pressure to examine the flame dynamics under different flow rates of guided ethylene and duty kerosene. The experimental results show that: Under high equivalence ratio conditions, the pulsation zone of guiding ethylene is primarily concentrated in the downstream region of the flameholder, and the dynamic characteristics of the flame are mainly influenced by Bénard-von Kármán (BVK) instability. When the ethylene supply is cut off and the kerosene burner operates independently, the flame dynamics are primarily characterized by volumetric oscillations and axial pulsations; When guided ethylene and duty kerosene are operated simultaneously, the flame dynamics within the V-shaped channel are primarily influenced by volume oscillations induced by heat release from combustion. Near the shear layer at the trailing edge of the flameholder, flame dynamics are predominantly affected by Kelvin-Helmholtz (KH) instability. When the guided ethylene equivalence ratio is relatively low, the dynamic characteristics of the flame near the trailing edge of the flameholder are primarily influenced by KH instability. As the equivalence ratio increases, the combustion zone gradually shifts downstream along the flameholder, and the dominant factor transitions from KH instability to BVK instability. When the guided ethylene flow rate is set to 2 g/s, increasing the duty kerosene fuel-air ratio from 0.003 4 to 0.008 5 has a negligible effect on the dynamic characteristics of the flameholder flame, and the frequency remains unchanged. A local optimum fuel-air ratio exists downstream of the flameholder. Continuing to add duty kerosene beyond this local optimum ratio will cause local fuel enrichment, thereby suppressing the flame's heat release pulsation.