Abstract

Asymmetrical shroud clearance, resulting from rotor-statpr eccentricity,causes so called aerodynamic forces, which in turn lead to self-excited vibrationsof rotor systems.Numerical investigations were carried out toshow how CFDcode can copewith determination of the pressure field in a rotor blade tip gap. Calculations of flows on the whole turbine stage circumference were performer in order to investigate the aerodynamic forces generated above the shroud due to asymmetrical pressure field caused by rotor-stator eccentrity. The 3D calculations of axial turbine of impulse type were performed using CFD code Fluent. Different types of shroud geometry were considered. The Multiple Reference Frame method and the Sliding Mesh method were applied and some of the results were compared with the experimental data. Both the techniques appeared to give results similar to those obtained in the experiments. The experimental investigations into the pressure field in the shroud clearence were performed on a one-stage air model turbine. The calcuations and measurements of pressure distribution were carries out for different rotor speeds and different turbine load.