EVALUATION OF COUPLED VIBRATIONS IN AERO-ENGINE COMPRESSOR BLADED DISK

Abstract

Natural frequency determination in aero engine compressor blading is highly important in the design of turbo-machines.  The difficulties faced by the designer during sizing of turbine blading are many. The major problem of design is a fair prediction of the natural frequencies of the compressor blading at the earlier stages. In general, a compressor blade is pre-twisted and tapered with an asymmetrical airfoil cross section and is mounted on the rotating turbine disk at a stagger angle. The differential equations of motion for the case of a single turbine blade are quite complex, and the solution of such equations is difficult to obtain. The present work deals with, establishing the best practice for coupled blade vibration analysis along with disk mode. The blade is considered to be mounted with the axis of symmetry in the plane of disk rotation. Simulation engineering is effectively utilized to analyze the blade and disk modes. Campbell diagrams are drawn at critical nodal diameters to arrive at separation margins in bladed disk assembly.