Experimental Study on the Cooling Performance of a Turbine Nozzle With an Innovative Internal Cooling Structure

Abstract

An innovative cooling structure named multi-slot cooling was invented for high-pressure turbine (HPT) nozzles and blades. This cooling structure has been designed to be simple, inexpensive, and to exhibit good cooling performance. In a previous study (GT2008-50444), the basic design data on the cooling effectiveness and pressure loss coefficients for HPT cooling design were obtained by using simple test pieces. In this study, the cooling performance of the HPT nozzle with a multi-slotted cooling structure in a cascade was reported. First, the HPT nozzle with a multi-slotted cooling structure and its outer profile were selected; its cooling structure was designed by using the data in the previous study and trial-and-error method. Subsequently, ceramic casting cores and casting nozzles were manufactured by way of trial. Furthermore the cooling performance test for the multi-slotted cooling nozzle (TEST #1) in an annular sector cascade test rig was conducted, and the cooling effectiveness fields and pressure loss data were obtained. In addition, the measurement test for determining the heat transfer coefficient on the nozzle (TEST #2) and that for determining the film cooling effectiveness on the nozzle (TEST #3) were conducted. And then, cooling performance of the multi-slotted cooling nozzle was evaluated by using these data. As a result, for the typical configuration, it was confirmed that the basic design data obtained in the previous study are applicable to designing nozzles with multi-slot cooling by introducing a minor modification and the cooling performance of multi-slot cooling is equivalent to that of the conventional cooling under the test condition; consequently, it was confirmed that the multi-slot cooling is well applicable to the cooling of actual HPT airfoils except in the case that its configuration is significantly changed.