Effects of Mixing Section Geometry on the Combustion Instability Characteristics in a Dump Shape Combustor

摘要

The main objective of this study was investigation of combustion instability characteristics in a lean partially premixed model gas turbine dump shape combustor. Dynamic pressure sensors were located on combustor and inlet section to observe combustion pressure oscillation and pressure difference at each place. Also heat release oscillation was measured using a high speed ICCD camera and PMT(Photomultiplier Tube). The inlet mixing section and combustor length were varied in order to have different acoustic characteristics from 470, 550, 870 mm inlet mixing section and 800 to 1680 mm of combustor section. In this study, shows the general behavior of combustion instability and stability map in model gas turbine combustor. And effects of combustor length, mixture velocity in the mixing section and equivalence ratio were studies by the pressure perturbation and heat release oscillation. The instability frequency and mode analysis were studied in last two sections. We observed two dominant instability frequencies in this study. Lower frequencies were obtained at lower equivalence ratio and it was associated with the fundamental longitudinal mode of combustor length. Higher frequencies were observed in higher equivalence ratio conditions. It was related to secondary longitudinal mode of combustor and mixing section. Also in this instability, pressure oscillation of mixing section was larger than pressure oscillation of combustor. As a result, combustion instability was strong affected by acoustic characteristics of combustor and inlet fuel-air feeding geometry.