Abstract

The trend in aviation engines with high specific power and, correspondingly, high aerodynamic loads leads to the problem of aeroelastic behaviour of blacles not only in compressors and fans, but also in turbines. Investigations of aeroelastic behaviour of the blades in dependence of structural mistuning are presented.

A numerical calculation method for unsteady aerodynanric characteristics of oscillating blade cascades under the action of instable loads is based on solution of the coupled fluid-structure problem, in which the aerodynamic ancl structural dynamic equations are integrated simultaneously in time, thus providing the correct formulation of a coupled problem, as the interblade phase angle, at which a stability (instability) woulcl occur, is a part of solution.

The icleal gas flow around multiple stage passages (with periodicity on the whole annulus) is described by the unsteady 2D Euler equations in conservative form, which are integrated by using the explicit monotonous second order accurate Godunov-Kolgan finite-volume scheme on the moving grid.

Th blade is modelled by a very simple two degrees of freedom discrete model. In this model cascade performs the torsional and the bending oscillations under the given law. The aeroelastic behaviour of the blades in the unsteacly aeroclynamic flow is calculatecl for the mistuned blades assenrblies of the Fourth and First Standarcl Configurations. The computational domain of the unsteady flow can not be restricted to the single blade passage. The results in the time domain analysis show the beneficial influence of the mistuning of the bending mode in comparison to the torsional mode. The dynamic properties of the mistunecl systems are dependent on the way of coupling of the blades, whether it is either aerodynamic or mechanical.