Numerical Study of a Gas Turbine's Shaft Cooling

Abstract

This paper focuses on the numerical study of a shaft's cooling, positioned at the end of the gas turbine hot section. Due to convection and conduction phenomena, the high temperatures of the primary gas flow are transferred -via the power turbine's blades and disk- to the power turbine's shaft. If the values of these transmitted temperatures are too high, in time, negative effects can occur, like: rotor imbalance or overheating the oil surrounding the power turbine's shaft. Therefore, for the turbine's shaft to operate properly, a cooling method must be applied. The cooling method considered in this study, is a secondary air flow path, which crosses through the labyrinth, part of the shaft itself and turbine's disk.In order to investigate the heat transfer between the secondary air flow and the turbine's shaft, several computations were performed, using the CFD software Ansys CFX. Several cases were analyzed, by modifying the geometry, the material, as well as the air mass flow passing through the analyzed path. The comparison between the different results led to the selection of the best configuration, in terms of cooling performances.