Stability Limits of GTE Axial Compressor Blade Rings for Subsonic Bending-Torsion Cascade Flutter on Stalling and Nonstalling Flow

Experimental studies on aerodamping (aeroexcitation) of blade profile vibrations in their aerodynamic coupling at different bending-torsion vibration modes and calculations of the stability limits of straight compressor cascades performed by the energy method with experimental aerodynamic profile shape factors are summarized. The critical reduced vibration frequencies K_cr of GTE axial compressor blade rings for bending-torsion coupling coefficients over the range of 0.5– 1.44 at the angles of attack of (–10)–20° and geometric cascade parameters (drift angle of 0–60° and relative pitch of 0.7–1.3) were evaluated. An independent increase in the bending-torsion coupling coefficient, angle of attack, drift angle, and a decrease in the relative cascade pitch are shown to cause an increase in the critical reduced vibration frequencies. At the same time, the quantitative K_cr is determined by the geometric cascade parameters, angle of attack, and bending-torsion coupling coefficient. The use of critical reduced vibration frequency values to assess the subsonic cascade flutter stability of the first stages of a modern AGTE high- and low-pressure compressor is exemplified. The stability limits obtained with the critical reduced vibration frequencies K_cr are in good agreement with experimental results for compressor cascade models.