Influence of the Constraint Equations in the Thermo-Mechanics Stress Analysis in Blades of Gas Turbine

The thermo-mechanical stresses analysis in an internally cooled first stage bucket, applying the finite element analysis (FEA) and computational fluid dynamics (CFD) is presented. In this analysis two cases are considered; first one where the model is solved using constraint equations in two zones, blade-platform and platform-root, obtaining the distribution of stresses which is in agreement with the physical problem, nevertheless due to the application of the constraint equations it was observed that the model has numerical limitations to obtain results. For the second case, without constraint equations, a geometry that include all the zones of the blade is achieved, generating a new mesh on which the same analysis was realized (thermo-mechanic) obtaining similar magnitudes of stresses like the first one model, but without numerical limitations. In both cases, the analysis was done using a complete model in 3D including the internal cooling channels. To carry out this analysis it was necessary to apply an interface FLUENT-ANSYS (FAI) to transfer the temperature data from an analysis obtained with a CFD model in steady state to the finite element model. A methodology was developed to eliminate to constraint equations in the finite element model across skills of union elements to achieve a uniform mesh in the whole model. The results show that an analysis without constraint equations, to avoid geometric simplifications and numerical limitations, permitting to obtain better results in the analysis of thermo-mechanics stress in blades of a gas turbine.