Detection and numerical analysis of the most efforted places in turbine blades under real working conditions

Blades of combustion turbines are elements which transfer an operative energy to an engine rotor. The blade consists of two pieces: a working piece called a profile covered by Thermal Barrier Coating (TBC) and a footer. The most dangerous parts of the blades are subjected to very high stress concentrations. They are situated in the profile section with the footer connection, where the maximum values of bending moments occur resulting from centrifugal forces and pressure of a working medium on the profile section.In the work we propose an extension of the turbine blade design strategy (in comparison to [5], [12] and [13]) by application of submodeling technique to perform more detailed analysis of damage process and progressive fracturing of the most efforted cross sections of the blade. In particular cracking direction of the TBC was analyzed numerically with application of the XFEM technique. The critical values of rotor speeds were estimated at which damage process initiates and further develops. The damage of TBC can lead to destruction of protective covering and exposures the whole turbine blade core (made of alloys) to sudden thermal shock.

► A new 3-D numerical model of the modern turbine blades was created with application XFEM.
► We propose an extension in the turbine blade design by application of submodeling technique.
► The model can be applied to the analysis of engineering structures with more complex shapes subjected to thermal shock.