Rapid Method of Predicting the Subsonic Flutter Stability of AGTE Axial-Flow Compressor Blade Cascades. Part 1. Physical Backgrounds of the Method

Abstract

Generalization of experimental investigation results for direct compressor cascades of blade profiles at a subsonic (continuous and separated) gas flow with bending, torsional, and bending-torsional vibrations created the basis for defining the physical mechanisms of subsonic flutter initiation in AGTE axial-flow compressor blade cascades. Such a combination of reduced frequencies and angles of attack is possible when the aerodynamic blade vibration decrement equals zero. It corresponds to the critical reduced vibration frequency value below which the aeroexcitation of blade vibrations and an increase in its level are observed, i.e., the dynamic subsonic cascade flutter loss is taking place. Known methods of evaluating these critical loss conditions are analyzed. The rapid method of predicting the dynamic subsonic flutter stability for compressor blade cascades is described. The scheme of critical reduced blade vibration frequency data base generation is tabulated as the critical values at fixed geometric cascade parameters (pitch-chord ratio and deflection angle), angles of attack, and coefficients of bending-torsional coupling. An example of such a data base for specific compressor blade cascades is given.