Abstract Modern gas turbine combustors usually adopt multi-nozzle lean premixed and pre-evaporated (LPP) combustion technology to reduce emissions. However, the thermoacoustic oscillation of this design poses a significant threat to the safe operation of gas turbines. This paper conducts experiments and numerical calculation studies on a diesel multi-nozzle LPP combustor to investigate the influence of its fuel staging ratio (FSR) on the flame structure and thermoacoustic oscillation. In the experiment, the pressure fluctuation and the self-luminescence images of OH* were measured simultaneously. The flow field and flame structure were obtained by RANS calculation. The results show that for the diesel multi-nozzle LPP combustor, increasing the FSR can suppress the thermoacoustic oscillation of the combustor, and the suppression ratio can reach 60%. When the pilot stage is not ignited, the oscillation mode is double-period limit loop oscillation, while after the pilot stage is ignited, the oscillation is single-period limit loop oscillation. The Proper Orthogonal Decomposition mode shows that the main energy of the oscillation is concentrated in the global axial synchronous oscillation. The Rayleigh index and numerical calculation results indicate that the change of FSR alters the flame distribution in the combustor. The increase of FSR causes the flame to develop from the interference zone between the wall and the main stage to that between the main stage and the pilot stage. The change of flame structure is the main reason for the suppression of thermoacoustic oscillation.
Lu et al. (Fri,) studied this question.