Measurement of Coarse Water Distribution in the L.P. Cylinders of Operating Steam Turbines

Abstract

SYNOPSIS The development of a ‘catchpot’ probe to measure coarse water flows (formed by deposition and re-entrainment, or agglomeration, of fog droplets) in the low pressure stages of a steam turbine is described. Theoretical considerations and laboratory calibration showed acceptable performance and accuracy limits. Results taken in three operating turbines at measuring stations situated downstream of the unshrouded penultimate and last row rotors are presented. These results show a peak in the radial distribution of the coarse water flow coinciding with the steam tip leakage region. The measured yaw angles of the coarse water flow agreed with the respective steam yaw angles except near the outer casing. The results are interpreted to give a simple model for the coarse water flows downstream of an unshrouded rotor and its implications for turbine design are discussed.