Turbomachine Blade Vibration

Fatigue failures of blades is one of the most vexing problems of turbomachine manufacturers, ever since the steam turbine became the main stay for power generating equipment and gas turbines are increasingly used in the air transport. The problem is very complex, involving the excitation due to aerodynamic stage interaction; damping due to material deformation, friction at slip surfaces and aerodynamic damping; vibration of an asymmetric aerofoil tapered along its length and mounted on a rotating disc at a stagger angle. The problem is also governed by heat transfer analysis and thermal stresses. His book deals with a basic understanding of free vibratory behaviour of turbine blades- free standing, packetted, and bladed-discs. The analysis is based on continuous and discrete models using energy principles and finite element techniques. A clear understanding of the interference phenomenon in a thin cambered airfoil stage in subsonic flow is presented to determine the nonsteady excitation forces acting on the blades. A comprehensive treatment on the blade damping phenomenon that occurs in turbines is given. The nonlinear damping models account for material damping and friction damping as a function of rotational speed for each mode. Resonant response calculation procedures for the steadily running as well as accelerating blades are given. Cumulative damage calculations are then outlined for fatigue life estimation of turbomachine blades. The book also deals with heat transfer analysis and thermal stress calculations which help in a comprehensive understanding of the blade problems. About the author: prof. J.s. Rao (hons.), m. Tech, ph.d., d.sc, taught at the indian institute of technology, kharagpur and delhi for over 30 years. He has also taught at the university of surrey, as a