Performance and Evaluation of a Thermally Optimized Gas Turbine Nozzle

Abstract This study evaluated the overall cooling effectiveness of a newly designed turbine airfoil using optimized internal and external cooling features. A symmetric airfoil, which incorporated advanced cooling schemes enabled by additive manufacturing, was designed for testing in a high temperature hydrogen fueled combustor facility. The design of this airfoil is described in a companion study. This paper describes the experimental and computational evaluation of the new design to ensure that the test model would have sufficient cooling to operate in the high temperature combustor. Tests were performed in a low temperature wind tunnel facility, matching the Mach number and Reynolds number of the combustor test facility. Further insight into the cooling performance and analysis of the experimental results was obtained using computational predictions. Experimental testing included a low conductivity model that was used to estimate adiabatic effectiveness for film cooling configurations. A high conductivity model, which matched the Biot number expected for operation in the combustor facility, was tested to obtain overall cooling effectiveness. Experimental results showed adiabatic effectiveness was generally above η¯ = 0.3, though there was a small region that fell below η¯. Overall cooling effectiveness was quite uniform ranging from ϕ¯ = 0.54 to 0.63 over the complete airfoil. Reynolds-Averaged Navier-Stokes (RANS) computations were consistent with the experimental trends. The RANS predictions were particularly useful in showing how conduction effects in the low temperature model were affecting the measurements of adiabatic effectiveness. The experiments and computational predictions verified that the design intent to have a relatively uniform overall effectiveness of greater than ϕ¯ = 0.55 was achieved. The study also identified deficiencies in the cooling design that could potentially be addressed leading to improved overall cooling effectiveness.