Multidisciplinary Prediction of Spatial-Temporal Evolution of Creep Damage on an Internally Cooled Turbine Vane

Abstract

One of the main causes of damage to gas turbine nozzle guide vanes (NGVs) is creep, which threatens the safety and reliability of gas turbines. Although creep life prediction has been applied to design and maintenance, creep damage is still frequently observed. Inadequate knowledge of the spatial-temporal evolution of creep damage makes it difficult to evaluate and accurately protect NGVs against abnormal creep damage. An integrated aero-thermal-structural simulation method based on conjugate heat transfer (CHT) computational fluid dynamics (CFD) and finite element method (FEM) is proposed to predict the spatial-temporal evolution of creep damage in the NGVs with internal cooling structures. In the temporal dimension, creep life is calculated by Larson-Miller parameters. In the spatial dimension, creep damage is characterized by a parametric modeling and CHT mesh generation procedure. The predicted results show that creep damage forms a groove or crack along the span at the leading edge of the suction side where the stress concentrates, which is similar to the frequently observed damage on the actual NGVs. The interactions between creep damage, flow, and heat transfer are discussed. The increase in turbine inlet temperature significantly shortens the time required for creep formation and evolution. It is suggested that creep damage through the NGV wall could radically alter the heat transfer and flow, resulting in a 30K increase in average leading edge temperature. As a result, the evolution of creep damage is self-promotingly accelerated.