EXPERIMENTAL AND NUMERICAL INVESTIGATION OF 2D PALISADE FLUTTER FOR THE HARMONIC OSCILLATIONS

Vladymir Tsimbalyuk, Anatoly Zinkovskii

Institute for Problems of Strength, Ukrainian National Academy of Sciences Ukrainian National Academy of Sciences, 2 Timiriazevskaia str., 01014 Kiev, Ukraine tsymb@yahoo. com

Vitaly Gnesin

Department ofAerohydromechanics, Institute for Problems in Machinery

Ukrainian National Academy of Sciences, 2/10 Pozharsky st., Kharkov 310046, Ukraine

gnesin@ipmach. kharkov. ua

Romuald Rzadkowski, Jacek Sokolowski

Institute ofFluid-Flow Machinery, Polish Academy ofSciences 80-952 Gdansk, ul. Fiszera 14, Polish Naval Academy z3@imp. gda. pl

Abstract The verification of the computational models for unsteady fbws through the os­cillating blade row becomes more difficult, because the experimental data for three-dimensional fbws are currently hardly available in the published litera­ture. Therefore comparisons between numerical methods and experimental ones for simple cascade geometry at inviscid flaw conditions must play an essential role in validation of the three – dimensional unsteady solution methods. In this study the numerical calculations were performed to compare the theoretical re­sults with experiments for the harmonic motion. The calculations were carried out for the torsional and bending oscillations of the compressor cascade. The comparison of the calculated and experimental results for different conditions of the cascade oscillations has shown the good quantitative and qualitative agree­ment.

Keywords: flitter, inviscid, blades

53

K. C. Hall et al. (eds.),

Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines, 53-63. © 2006 Springer. Printed in the Netherlands.

1. Introduction

Cases of flitter-type instability are sometime encountered in the course of developing new gas turbine engines. Costly testing is necessary to eliminate this problem. One of the main problems in predicting flitter at the engine de­sign stage is determining the transient aerodynamic loads that develop during the vibrations of blades. This problem is particularly important in the case of separated fl»w, when theoretical methods of determining the transient aerody­namic loads are not yet sufficiently reliable. Thus, in this study, we use an experimental method of determinate the transient aerodynamic loads on the vibrating blades of turbine engine.

It is quite difficult to measure the aerodynamic loads along the blades during rotation of the blading ring. Thus, with allowance for the three-dimensional nature of the air fbw about the ring, the cylindrical sections of the ring are often modeled as vane cascades. When such a cascade is placed in a wind tunnel, the fl>w parameters, geometric characteristics, and vibration parameters should be constant along the vanes.

The aeroelastic results of bending vibrations of 2D linear cascade in sub­sonic fl>w were published by Kaminier and Stel’makh 1996 and torsional Kaminier et al. 1988. The experimental results of aero-damping and dynamic stability of compressor cascades under bending-torsional vibrations were pre­sented in Len et al. 1986.

Useful benchmark data, which became a de facto standard for unsteady cas­cade fl>ws, can be found in Bolcs and Fransson 1986 for the EPFL series of Standard configurations.

Aerodynamic loads are measured indirectly either through the aerodynamic damping of bladed vibrations by Kaminier and Nastenko 1973 or the distribu­tion of transient pressures on the blade surfaces Tanaka et al. 1984. They are measured directly with an extensometric dynamometer Kimura and Nomiyama 1988 or on the basis of the forces developed by vibrators Kaminier at el. 1988.

In the Institute for Problem of Strength of NAS of Ukraine the proper 2D experimental bench was developed to measure simultaneously unsteady aero­dynamic force and moment with arbitrary combinations of motions y and a of airfoil cascades in the subsonic flow. Description of such test bench is given in paper Tsimbalyuk et al. 2002.