The Influence of Moisture Content on Energy Losses in the Steam Turbine Last Stages

Abstract

A method for calculating energy losses due to moisture content is presented, which takes into account the intra-channel and peripheral separation in condensing steam turbine LPC last stages and the actual moisture distribution over the stage height. It is shown that with the consideration of peripheral and intra-channel separation in the stage with a 1200-mm long rotor blade, the losses due to moisture content are decreased by 1.3% and, accordingly, stage efficiency hrist is increased by the same value. If the separated moisture is distributed taking into account the location of the intra-channel separation slots, and the separated peripheral moisture is distributed according to a linear law in the stage upper quarter, the real moisture content value at the periphery will decrease by 8%. This will make it possible to more accurately take into account the rotor blade droplet impingement erosion at the blade peripheral zone inlet section. It is recommended to calculate the energy losses due to moisture content not in the internal relative efficiency hri as part of additional losses, but inside the blade efficiency hrb, because these losses take place in the stage cascades, unlike other types of additional losses. This approach will help more accurately determine the following flow characteristics in the stage: relative velocities M1 and M2, velocity coefficients in the nozzle j and rotor y cascades, stage reaction ratio r, etc.