Thermoelastic eigenfrequency of pre-twisted FG-sandwich straight/curved blades with rotational effect

This work focuses on the dynamic analysis of thermal barrier coated straight and curved turbine blades modelled as functionally graded sandwich panel under thermal environment. The pre- twisted straight/curved blade model is considered to be fixed to the hub and, the complete assembly of the hub and blade are assumed to be rotating. The functionally graded sandwich composite blade is comprised of functionally graded face-sheet material and metal alloy core. The constituents' material properties are assumed to be temperature-dependent, however, the overall properties are evaluated using Voigt's micromechanical scheme in conjunction with the modified power-law functions. The blade model kinematics is based on the equivalent single-layer shear deformation theory. The equations of motion are derived using the extended Hamilton's principle by including the effect of centrifugal forces, and further solved via 2D- isoparametric finite element approximations. The mesh refinement and validation tests are performed to illustrate the stability and accurateness of the present model. In addition, frequency characteristics of the pre-twisted rotating sandwich blades are computed under thermal environment at various sets of parametric conditions such as twist angles, thickness ratios, aspect ratios, layer thickness ratios, volume fractions, rotational velocity and blade curvatures which can be further useful for designing the blade type structures under turbine operating conditions.

Automated summary

This study focuses on the dynamic analysis of thermal barrier coated straight and curved turbine blades, which are modeled as functionally graded sandwich panels in a thermal environment. The findings reveal that the functionally graded sandwich composite blade is made up of a functionally graded face-sheet material and a metal alloy core, with temperature-dependent material properties. The overall properties are evaluated using Voigt's micromechanical scheme and the modified power-law functions. The blade model uses the equivalent single-layer shear deformation theory, and the equations of motion are derived using the extended Hamilton's principle and solved using 2D-isoparametric finite element approximations. Mesh refinement and validation tests are conducted to demonstrate the stability and accuracy of the model. Additionally, the frequency characteristics of the pre-twisted rotating sandwich blades are computed under various parametric conditions, providing useful insights for designing blade type structures for turbine operations.