Thermo-Mechanical Transient Analysis and Conceptual Optimization of a First Stage Bucket Available to Purchase

This paper presents a thermo-mechanical analysis of a first stage bucket during a gas turbine start-up. This analysis uses two simulation techniques, Computational Fluid Dynamics (CFD) for the conjugate heat transfer and flow analysis, and Finite Element Analysis (FEA) for the thermo-structural analysis. Computational three dimensional models were developed using two commercial codes, including all elements of the real bucket, to avoid geometric simplifications. An interface was developed to transfer the three-dimensional behavior of bucket temperatures during turbine start-up from CFD analysis to subsequent FEA analysis, imposing them as a thermal load. This interface virtually integrates the computational models, although they have different grids. The results of this analysis include temperature evolution and related stresses, as well as the thermo-mechanical stresses and zones where they are present. These stresses are dominated by thermal mechanisms, so a new temperature start-up curve is proposed where the maximum calculated stress decline around 100 MPa, and almost all stresses are lower throughout the transient analysis. The results are compared to experimental data reported in the literature obtaining acceptable approximation.