Mechanisms for Wide-Chord Fan Blade Flutter

This paper describes a detailed wide-chord fan blade flutter analysis with emphasis on flutter bite. The same fan was used with three different intakes of increasing complexity to explain flutter mechanisms. Two types of flutter, namely, stall and acoustic flutters, were identified. The first intake is a uniform cylinder, in which there are no acoustic reflections. Only the stall fiutter, which is driven by flow separation, can exist in this case. The second intake, based on the first one, has a "bump" feature to reflect the fan's forward pressure wave at a known location so that detailed parametric studies can be undertaken. The analysis revealed a mechanism for acoustic flutter, which is driven by the phase of the reflected wave. The third intake has the typical geometric features of a flight intake. The results indicate that flutter bite occurs when both stall and acoustic flutters happen at the same speed. It is also found that blade stiffening has no effect on aero-acoustic flutter.

[1]  Kivanc Ekici,et al.  Multistage Coupling for Unsteady Flows in Turbomachinery , 2005 .

[2]  Abdulnaser I. Sayma,et al.  Modeling of Three-Dimensional Viscous Compressible Turbomachinery Flows Using Unstructured Hybrid Grids , 2000 .

[3]  L. He.  INTEGRATION OF 2-D FLUID/STRUCTURE COUPLED SYSTEM FOR CALCULATIONS OF TURBOMACHINERY AERODYNAMIC/ AEROELASTIC INSTABILITIES , 1994 .

[4]  Abdulnaser I. Sayma,et al.  Mechanisms and Prediction Methods for Fan Blade Stall Flutter , 2001 .

[5]  O. O. Bendiksen,et al.  Recent Developments in Flutter Suppression Techniques for Turbomachinery Rotors , 1988 .

[6]  F. O. Carta,et al.  Coupled Blade-Disk-Shroud Flutter Instabilities in Turbojet Engine Rotors , 1967 .

[7]  Abdulnaser I. Sayma,et al.  Computational Study of Intake Duct Effects on Fan Flutter Stability , 2002 .

[8]  Abdulnaser I. Sayma,et al.  On the Use of Atmospheric Boundary Conditions for Axial-Flow Compressor Stall Simulations , 2005 .

[9]  Edward F. Crawley,et al.  Parametric Trends in the Flutter of Advanced Turboprops , 1989 .

[10]  Mehmet Imregun,et al.  A review of aeroelasticity methods with emphasis on turbomachinery applications , 1996 .

[11]  A. V. Srinivasan,et al.  Some Recent Advances in the Understanding and Prediction of Turbomachine Subsonic Stall Flutter , 1985 .

[12]  P. Spalart.  A One-Equation Turbulence Model for Aerodynamic Flows , 1992 .

[13]  Joseph M. Verdon,et al.  A linearized unsteady aerodynamic analysis for transonic cascades , 1984, Journal of Fluid Mechanics.

[14]  Nigel Peake,et al.  Trapped acoustic modes in aeroengine intakes with swirling flow , 2000, Journal of Fluid Mechanics.

[15]  Frank Lane,et al.  System Mode Shapes in the Flutter of Compressor Blade Rows , 1956 .