A Novel Multi-Stage Impingement Cooling Scheme—Part II: Design Optimization

Cross flow and coolant maldistribution are the common design challenges for impingement cooling in modern gas turbine. This paper reports a novel multi-stage impingement cooling scheme for combustor liner. The design concept and general working mechanism are introduced in the Part I paper. This Part II paper presents the design flexibilities and optimization strategies. Conjugate heat transfer (CHT) analysis was conducted at a range of Reynolds numbers to assess the thermal performance, loss penalty, and the working mechanism behind. The results show that varying the jet hole diameter in each cooling stage can be an effective design optimization strategy in balancing the cooling requirement and loss penalty. Inter-stage bypass design is also another design flexibility offered by the multi-stage scheme to regulate the cooling air consumption at different stages. With these optimization strategies, the target surface temperature and local gradient can be effectively reduced with reasonable pressure loss with 50% reduction in the cooling air consumption compared to conventional single-stage impingement design. This multi-stage impingement concept can be practically applied to gas turbine combustor liner and turbine blade cooling.