https://www.sciencedirect.com/science/article/pii/S1290072924007476?dgcid=coauthor

Aero-engines firing gas or liquid fuel often suffer from self-excited thermoacoustic instability (SETAI). The fuel mass flowrate (F_P) strongly influences the SETAI condition, but existing experimental data do not provide a consistent explanation for the mechanism. Based on the effects of the premixed chamber length (L_P) and equivalence ratio (φ) on SETAI, this study investigates how F_P affects the SETAI state and the combined effect of these three parameters. F_P influences the total heat release and temperature within the combustion chamber, thus affecting the local acoustic speed and modifying the sound pressure wavelength (λ_P) in the premixed chamber. Lower values of F_P lead to higher λ_P, which then requires a larger value of L_P to achieve a similar phase difference between the pressure oscillations and flowrate oscillations. φ mainly affects the reaction time-lag, and consequently determines the phase difference between flowrate oscillations and heat release oscillations. These factors combine to affect the phase difference between pressure oscillations and heat release oscillations, thus determining the SETAI state according to Rayleigh's criterion. The mechanisms explain some ostensibly conflicting observations of the SETAI variation trends with increasing F_P in previous reports.