Thermo-elastodynamic coupled model to obtain natural frequency and stretch characteristics of a rotating blade with a cooling passage

Abstract

Gas turbines are operated at high temperatures for increased thermal efficiencies and power outputs. To protect turbine blades from high temperatures and to meet the proper durability requirements, superalloys and cooling passages are widely used. The employment of cooling passages results in significant variations in the temperatures of the blades. Owing to these temperature variations, there are significant variations in the material properties of the blades. Further, the variations in the material properties should be considered to develop a structural dynamic model. In this paper, an enhanced thermo-elastodynamic coupled model of a rotating superalloy blade under thermal loading conditions is proposed. In particular, a nonlinear heat transfer equation was solved to obtain an accurate temperature distribution along the cross-section of the blade. With an increase in the surface temperature, there was a decrease in the first natural frequency and an increase in the stretched length of the blade. The accuracy of the proposed model was validated by comparing the natural frequencies and stretched lengths of the rotating blade obtained using the proposed model with those obtained using a commercial finite element code. The findings of this study highlight the necessity of employing an accurate thermo-elastodynamic coupled model for the design of gas turbine blades operated at high temperatures.