Turbine Vane Passage Cooling Experiments With a Close-Coupled Combustor-Turbine Interface Geometry Part II: Describing the Coolant Coverage

The first-stage gas turbine vane surfaces and endwalls require aggressive cooling. This two-part paper introduces a modified design of the combustor-turbine (C-T) interface, the "close-coupled interface," that is expected to increase cooling performance of vane passage surfaces. While Part I of the paper describes secondary flows and coolant transport in the passage, this part discusses the effects of the new C-T interface geometry on adiabatic cooling effectiveness of the endwall and vane surfaces. Compared to the traditional C-T interface, the coolant requirement is reduced for the same level of cooling effectiveness on all three surfaces for the new C-T interface design, confirming that it is an improvement over the previous design. The endwall crossflow is reduced by combustor coolant injection with the new interface leading to more pitchwise-uniform cooling of the endwall. For the pressure surface, increasing combustor coolant flowrate directly increases phantom cooling effectiveness and spreading of coolant away from the endwall. With the traditional passage vortex seen in the literature replaced by the impingement vortex of the present design, the suction surface receives less phantom cooling than does the pressure surface. However, cooling performance is still improved over that of the previous C-T interface design.