Journal ArticleDOI
Flutter of swept fan blades
Robert E. Kielb,K. R. V. Kaza +1 more
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TLDR
In this article, the effect of sweep on fan blade flutter was studied by applying the analytical methods developed for aeroelastic analysis of advance turboprops, and it was shown that sweep has a beneficial effect on torsional flutter and a detrimental effect on bending flutter.Abstract:
The effect of sweep on fan blade flutter is studied by applying the analytical methods developed for aeroelastic analysis of advance turboprops. Two methods are used. The first method utilizes an approximate structural model in which the blade is represented by a swept, nonuniform beam. The second method utilizes a finite element technique to conduct modal flutter analysis. For both methods the unsteady aerodynamic loads are calculated using two dimensional cascade theories which are modified to account for sweep. An advanced fan stage is analyzed with 0, 15 and 30 degrees of sweep. It is shown that sweep has a beneficial effect on predominantly torsional flutter and a detrimental effect on predominantly bending flutter. This detrimental effect is shown to be significantly destabilizing for 30 degrees of sweep.read more
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Journal ArticleDOI
Numerical Investigation of the Effect of Design Parameters on the Blade Flutterr Prediction
TL;DR: A study of the influence of the design parameters on prediction of blade flutter in compressors of gas-turbine engines is presented and it is shown that the inter-blade tension has a significant influence on theFlutter boundaries, while the effect of other design parameters under investigation on the flutter boundaries is insignificant.
DissertationDOI
Embedded blade row flutter
Abstract: Modern gas turbine design continues to drive towards improved performance, reduced weight and reduced cost. This trend of aero-engine design results in thinned blade aerofoils which are more prone to aeroelastic problems such as flutter. Whilst extensive work has been conducted to study the flutter of isolated turbomachinery blades, the number of research concerning the unsteady interactions between the blade vibration, the resulting acoustic reflections and flutter is very limited. In this thesis, the flutter of such embedded blade rows is studied so as to gain understanding as for why and how such interactions can result in flutter. It is shown that this type of flutter instability can occur for single stage fan blades and multi-stage core compressors. Unsteady CFD computations are carried out to study the influence of acoustic reflections from the intake on flutter of a fan blade. It is shown that the accurate prediction of flutter boundary for a fan blade requires modelling of the intake. Different intakes can produce different flutter boundaries for the same fan blade and the resulting flutter boundary is a function of the intake geometry in front of it. The above finding, which has also been demonstrated experimentally, is a result of acoustic reflections from the intake. Through in-depth post-processing of the results obtained from wave-splitting of the unsteady CFD solutions, the relationship between the phase and amplitude of the reflected acoustic waves and flutter stability of the blade is established. By using an analytical approach to calculate the propagation and reflection of acoustic waves in the intake, a novel lowfidelity model capable of evaluating the susceptibility of a fan blade to flutter is proposed. The proposed model works in a similar fashion to the Campbell diagram, which allows one to identify the region (in compressor map) where flutter is likely to occur at early design stages of an engine. In the second part of this thesis, the influence of acoustic reflections from adjacent blade rows on flutter stability of an embedded rotor in a multi-
Aeroelastic stability and response of rotating structures
Theo G. Keith,T. S. R. Reddy +1 more
TL;DR: In this paper, aero-elastic analysis for predicting flutter and forced response in fans, compressors, and turbines using computational fluid dynamic (CFD) methods is presented.