Identification and mapping of early thermoacoustic phenomena in gas turbine test rig

In this paper, an optical approach is tested to spatially characterize combustion fluctuations in a single burner atmospheric gas turbine test rig. The target of present investigation was to test two different techniques with the aim to characterize the thermoacoustic behavior of burners during combustion tests campaign. The analysis based on fast infrared imaging of flames, coupled with dynamic pressure transducers and photomultiplier measurements, has been elaborated on a 3 MW gas turbine test rig equipped with full scale burner tested in atmospheric conditions. The rig has been purposely designed to be tuned on acoustic frequencies detected in real gas turbine machine equipped with 24 burners and operating at 20 bar. In atmospheric test campaign the burner evidenced main oscillations at low frequencies around 82 Hz and 146 Hz. These frequencies have been recorded in real machine too. The technique allowed identifying these frequencies in the 2D dimensions under humming conditions. The developed tool has enabled to design a methodology for comparing different burners operating in different conditions from thermoacoustic point of view.