TY - GEN
T1 - Computational study of stall flutter in linear cascades
AU - Abdel-Rahim, A.
AU - Sisto, F.
AU - Thangami, S.
N1 - Publisher Copyright:
Copyright © 1991 by ASME.
PY - 1991
Y1 - 1991
N2 - Aeroelastic interaction inturbomachinery is of prime interest to operators, designers and aeroelasticians. Operation at off-design conditions may promote blade stall; eventually the stall pattern will propagate around the blade annulus. The unsteady periodic nature of propagating stall will force blade vibration and blade flutter may occur if the stall propagation frequency is entrained by the blade natural frequency. In this work a computational scheme based on the vortex method is used to simulate the How over a linear cascade of airfoils. The viscous effect is confined to a thin layer which determines the separation points on the airfoil surfaces. The preliminary structural model is a two-dimensional characteristic section with a single degree of freedom in either bending or torsion. A study of the relationship between the stall propagation frequency and the blade natural frequency has been conducted. The study shows that entrainment, or frequency synchronization, occurs resulting in pure torsional flutter over a certain interval of reduced frequency. A severe blade torsional amplitude (of order 20°) has been computed in the entrainment region reaching its largest value in the center of the interval. However, in practice, compressor blades will not sustain this vibration and blade failure may occur before reaching such a large amplitude. Outside the entrainment interval the stall propagation is shown to be independent of the blade natural frequency. In addition, computational results show that there is no entrainment in the pure bending mode. Rather "de-entrainment" occurs with similar flow conditions and similar stall frequencies, resulting in blade buffeting in pure bending.
AB - Aeroelastic interaction inturbomachinery is of prime interest to operators, designers and aeroelasticians. Operation at off-design conditions may promote blade stall; eventually the stall pattern will propagate around the blade annulus. The unsteady periodic nature of propagating stall will force blade vibration and blade flutter may occur if the stall propagation frequency is entrained by the blade natural frequency. In this work a computational scheme based on the vortex method is used to simulate the How over a linear cascade of airfoils. The viscous effect is confined to a thin layer which determines the separation points on the airfoil surfaces. The preliminary structural model is a two-dimensional characteristic section with a single degree of freedom in either bending or torsion. A study of the relationship between the stall propagation frequency and the blade natural frequency has been conducted. The study shows that entrainment, or frequency synchronization, occurs resulting in pure torsional flutter over a certain interval of reduced frequency. A severe blade torsional amplitude (of order 20°) has been computed in the entrainment region reaching its largest value in the center of the interval. However, in practice, compressor blades will not sustain this vibration and blade failure may occur before reaching such a large amplitude. Outside the entrainment interval the stall propagation is shown to be independent of the blade natural frequency. In addition, computational results show that there is no entrainment in the pure bending mode. Rather "de-entrainment" occurs with similar flow conditions and similar stall frequencies, resulting in blade buffeting in pure bending.
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U2 - 10.1115/91-GT-005
DO - 10.1115/91-GT-005
M3 - Conference contribution
AN - SCOPUS:84924787978
T3 - Proceedings of the ASME Turbo Expo
BT - Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award; General
T2 - ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition, GT 1991
Y2 - 3 June 1991 through 6 June 1991
ER -