Tangential Mode Combustion Oscillation of a Bluff-Body-Stabilized Diffusion Flame: Experiments

Abstract

Addressing the issue of tangential mode combustion oscillation prevalent in aviation engine afterburners, this study targets bluff body diffusion flames. Innovatively, acoustic cavities were installed on either side of the bluff body flame, forming a tangential mode oscillation. The study employed experimental methods to study the flame pulsation characteristics under tangential oscillation, identifying the phase distribution of the flame front as a distinct feature differentiating it from conventional longitudinal mode oscillation. Furthermore, it was noted that the multiperiodic pulsation of the flame surface significantly contributes to the complex variability of the flame transfer function/flame description function. The research then established a phase relationship among velocity pulsation, pressure pulsation, and heat release rate pulsation, uncovering the phase coupling mechanism inherent in oscillatory combustion. It also delved into the impact of equivalence ratio and bluff body structure on tangential mode oscillation. Modifications to the bluff body structure led to a significant suppression of oscillation, reducing the amplitude by up to 81.3%. Thus, the study concluded that the flame dynamic response characteristics play a crucial role in determining the thermoacoustic coupling intensity, especially when the combustion system’s acoustic properties are stable. This finding lays a theoretical foundation for future endeavors to mitigate tangential mode oscillatory combustion in afterburners.