Computational study of stall flutter in linear cascades

A. Abdel-Rahim, F. Sisto, S. Thangami

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

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.

Original languageEnglish
Title of host publicationManufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award; General
ISBN (Electronic)9780791879023
DOIs
StatePublished - 1991
EventASME 1991 International Gas Turbine and Aeroengine Congress and Exposition, GT 1991 - Orlando, United States
Duration: 3 Jun 19916 Jun 1991

Publication series

NameProceedings of the ASME Turbo Expo
Volume5

Conference

ConferenceASME 1991 International Gas Turbine and Aeroengine Congress and Exposition, GT 1991
Country/TerritoryUnited States
CityOrlando
Period3/06/916/06/91

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