Effects of combustor wall cooling structure on combustor performances

Abstract

For lean premixed low-emissions gas turbine combustors, the amount of air used for combustion chamber cooling is relatively low to maintain a “lean” state of the flame. However, the wall cooling structures may have significant effects on combustor performances such as pollutant emissions, outlet temperature distributions, and boundary temperatures since it can change the near-wall temperature distributions. Most of the existing studies focus on the influence of cooling hole structures on heat transfer characteristics, and few studies comprehensively investigate the comprehensive effects on the wall heat transfer, outlet temperature distribution, pollutant generation characteristics, flow field structure, and flame morphology. To explore the feasibility of enhancing combustor performance through the implementation of combustor wall cooling structures, this study conducted a series of experimental and numerical investigations using two combustion chamber liners. Results show that although the burner structure remains unchanged, using the improved liner can widen the low-emissions operation ranges, and will reduce CO emissions by 49.34 % under low-power operating conditions and NOx emissions by 7.95 % under high-power operation conditions. This is because it optimizes the distribution of the wall temperature gradient and the shape of the corner recirculation zone. Besides, the improved structure enhances the boundary wall heat transfer by about 10 %, which leads to a 14.31 K lower and more uniform temperature of the liner. This is because it eliminates the cooling air incident vortex and improves the heat transfer between different rows of cooling holes. Due to the change of flow-field and near-wall temperature distribution, the optimum fuel supply strategy is different for the two liner structures. In particular, the optimal fuel staging strategy for the original liner necessitates a higher inner stage equivalence ratio than that required for the improved liner configuration. The results of this study offer a solution strategy for effectively improving combustor performances by employing suitable liner cooling tactics.