STATOR-ROTOR AEROELASTIC INTERACTION FOR THE TURBINE LAST STAGE IN 3D TRANSONIC FLOW

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

Vitaly Gnesin, Luba Kolodyazhnaya

Department ofAerohydromechanics, Institute for Problems in Machinery

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

gnesin@ipmach. kharkov. ua

Abstract A three-dimensional numerical analysis for aerodynamic unsteady forces and flitter parameters of the last stage steam turbine 13K215 rotor blades have been presented. The low frequency excitation was simulated for a 94 rotating blades with 54 nozzles. It was assumed that the pressure behind the rotor blades is changing in the circumferential direction. The flitter parameters of this stage were calculated.

1. Introduction

The classical and partial integration flitter analysis (Bakhle et al. 1992, He 1994; Moyround et al. 1996, Rzadkowski 1998, Rzadkowski and Gnesin 2000, 2001, He and Ning 1998, Bendiksen 1998, Gnesin et al. 2000, 2001, Carstens and Belz 2000) take into consideration only the rotor blades. The stator blades are modelled by the interblade phase angle of the rotor blades as the initial condition.

Hall and Silkowski 1997 can be cited as one of a few papers investigating into the effect of neighbouring blade rows. Namba and Ishikawa 1983 give an analytical study on contra-rotating annular cascades with oscillating blades. For the first time the coupled solution of an aeroelastic problem for turbine

569

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

Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines, 569-580. © 2006 Springer. Printed in the Netherlands.

stage with vibrating blades was presented by Rzadkowski and Gnesin 2002 for uniform distribution of the pressure behind the rotor blade.

In this paper a three-dimensional numerical analysis for aerodynamic un­steady forces of the last stage steam turbine 13K215 rotor blades have been presented for non-uniform pressure distribution behind the rotor blades.

The numerical calculation of the 3D transonic ft>w of an ideal gas through turbomachinery blade rows moving relatively one to another without taking into account the blades oscillations is presented.

An ideal gas ft>w through the mutually moving stator and rotor blades with periodicity on the whole annulus is described by the unsteady Euler conser­vation equations, which are integrated using the explicit monotonous finite – volume difference scheme of Godunov-Kolgan and moving hybrid H-H grid.

It was assumed that the pressure behind the rotor blades is changing in the circumferential direction (measured by the angle around the axis of rotation of the turbine). For circumferential angle ( а Є (0, 90°) p2=6000 Pa, а Є (90°, 180°) p2=7500 Pa, а Є(180°, 270°) p2=9000 Pa, а Є (270°, 360°) p2=7500 Pa. The unsteady forces acting on the ith rotor blades, in axial, tangential and radial directions were found.