Acoustic Diagnostics Applications in the Study of the Oscillation Combustion in Lean Premixed Pre-Evaporation Combustor

Abstract

The paper presents an experimental investigation of the thermoacoustic oscillations detection in a lean premixed pre-evaporation (LPP) combustor using acoustic signals. The LPP model combustion chamber oscillation combustion test platform was designed and built, and the combustion chamber oscillation combustion conditions of the sound - pressure - thermal parameters contrast experiment was complete. In this experiment, the thermal parameters signal, the acoustic signal and the dynamic pressure signal were collected under the oscillation state and the transition state (ignition condition, stable to the oscillation combustion condition, the oscillation to the stable combustion condition and the flameout condition), and been analyzed comparatively. The experimental result shows that the acoustic signal and pressure signal can reflect the changing of the main frequency in the combustion chamber. That is, at the same inlet air flow, the main frequency of the combustion chamber is proportional to the thermal load, while at the same fuel flow, the main frequency of the combustion chamber does not change with the changing of air flow. In addition, the frequency multiplication of the acoustic signal is more obvious than the pressure signal’s, which show that the interference of the acoustic signal is less, it can clearly reflect the thermoacoustic oscillation in the combustion chamber. In the transition state, the pulse energy of the acoustic signal is obviously increased after ignition. The main frequency energy increases when the working condition begins to change in the stable to the oscillation combustion condition. The main frequency energy decreases when the working condition begins to change in the oscillation to the stable combustion condition. During the flameout condition, the oscillating energy begins to decay from the high frequency region. For the acoustic signal is less disturbed than the pressure signal and it can obtained the same result with the pressure signal in the oscillation state and the transition state, it can replace the pressure signal in the thermoacoustic coupling oscillation analysis of the lean premixed pre-evaporation combustor the lean premixed pre-evaporation combustor.