Effects of Wall Confinement on the Flame Topology and Lean Blowout Characteristics in A Partially Premixed Single Swirl Gas Turbine Model Combustor

This work investigated the effects of wall confinement on lean blowout (LBO) characteristics of partially premixed methane/air flames in a single swirl gas turbine model combustor (GTMC). Two different swirlers with flat and fillet sleeve structures (SWA and SWB) were adopted under fully confined and unconfined conditions for comparison. The velocity field characteristics were measured by 2D Particle Image Velocimetry (PIV), while the flame macrostructures were obtained by CH* chemiluminescence imaging. Distinctively, different types of flame shapes and flow field patterns were observed under fully confined and unconfined conditions and an evident transition of flow field topology from nonreacting to reacting cases related to the Coanda effect was only found in the SWB cases. The results show that the confined flames have a larger expansion angle than the unconfined, and the LBO limits (ϕLBO) shift to much higher equivalence ratios corresponding to better stability performance. Additionally, the ϕLBO characteristics present a slight difference between the SWA and SWB cases, and the Reynolds number (Re) also has a limited effect. Thus, wall confinement is a dominant factor that affects the flame topology and ϕLBO which should be considered in practical gas turbine applications.