HCF Assessment of Gas Turbine Compressor Disc

A numerical assessment of a high pressure compressor subjected to speed and pressure loading is presented in this paper. The disturbances originate from pressure gain in the compression processes, such as aeromechanics pressure and angular velocity of the rotors is considered for the assessment. Their unsteady behavior is investigated to ensure the structural integrity of the rotating Disc. Furthermore, blade excessive vibration (leading to high cycle fatigue) must be avoided, especially under the additional excitation frequencies from waves traveling upstream of the compressor. Two main numerical analyses are presented, contrasting undisturbed with disturbed operation of a typical aircraft engine compressor. The first part of the paper evaluates frequency parameters for a representative blisk stage with high-accuracy 3D cyclic symmetry analysis. A Campbell diagram is plotted to understand the resonances caused due to engine orders in the gas turbine. Later an Interference diagram is plotted to understand the interactions of the disc and airfoil of the blisk as well as pressure and temperature unsteady damping are determined for a broad range of disturbances. The harmonic balance method is used to determine the aerodynamic damping. The second part provides the aeroelastic harmonic forced response of the rotor blades, with structural damping and forcing obtained from the unsteady calculations in the first part. The influence of blade mode shapes, nodal diameters and forcing frequency matching is also examined.