UNSTEADY FORCES ACTING ON THE ROTOR BLADES AND SHAFT IN THE CONTROL STAGE FOR DIFFERENT STEAM ADMISSION VARIANTS

摘要

This paper concerns the unsteady high- and low-frequency excitation forces acting on the rotor blades and shaft in the control stage of a 200 MW steam turbine. An ideal gas flow through mutually moving stator and rotor blades was described in the form of unsteady Euler conservation equations, which were integrated using the Godunov-Kolgan explicit monotonous finite-volume difference scheme and a hybrid H-H grid. The effect of rotor blade mistiming on the unsteady forces acting on both the blades and the shaft was examined. Four different control stage steam admission variants were analysed. The actual levels of the stationary components of particular forces were determined by changes in the operating conditions of individual nozzle segments. Different mistuning variants generated different distributions of unsteady rotor blade force harmonics. The presented results show that the first harmonic does not always dominate the spectrum. When considering forces acting on the rotor blades and shaft, there exists an optimal procedure of turbine start-up.