Numerical study of the self-excited thermoacoustic vibrations occurring in combustion system

Much attention has been paid to the effects of Reynolds number, equivalence ratio, and acoustic excitation on vibration frequency and amplitude in the previous studies on thermoacoustic vibrations, while little work has been published on the factors affecting the occurrence of vibrations in combustion system. The self-excited thermoacoustic vibrations in a two-dimensional combustion system were studied with a numerical method in the present study. The effects of inlet boundary condition and fuel-air feed channel length on the occurrence of thermoacoustic vibrations, the vibration mode, and the vibration frequency were investigated. The results showed that the self-excited thermoacoustic vibrations during combustion process were successfully captured by numerical simulations. The waveform of the standing wave formed in the channel-chamber coupled system was influenced by the inlet boundary condition and the channel length. Only when a pressure node rather than a pressure antinode occurred upstream of the interface, and the reaction heat release zone was close to the pressure antinode in the combustion chamber, could the Rayleigh criterion be fulfilled and consequently the vibration be encouraged. In addition, the vibration mode and the vibration frequency were also affected by the inlet boundary condition and the channel length.