To the issue of choosing surface roughness for the nozzle and rotor blades of steam turbines

Abstract

DOI: https://doi.org/10.32820/2079-1747-2020-25-152-158

The paper considers the choice of surface roughness for nozzle and rotor blades of steam turbines. The complexity of this problem results from factors such as labour content, manufacturing cost, availability of technological equipment, the estimated reduction in losses in the flow part, the duration of preservation of the surface roughness during operation of turbines, etc. The analysis of theoretical and experimental studies indicates a significant effect of the streamlined surface blades roughness on profitability and fatigue strength of steam turbine blading, as well as insufficiently formulated requirements of acceptable roughness that would ensure maximum efficiency of turbines. Of all the existing regulatory documents, in fact, only one determines the requirements to surface roughness of the blades active part, while it does not sufficiently take into account the range of Ukrainian blades chord used, as well as non-compliance with the requirements of the methodological guidelines regarding the selection of acceptable roughness takes place. It is concluded that it is necessary to create a calculation methodology to increase the efficiency of flowing parts of steam turbines based on the study of the surface roughness for the nozzle and rotor blade profile, as well as the creation of relevant regulatory documentation. Increasing the surface roughness of nozzle and rotor blades makes it possible to reduce the intensity of the salts drift of the flowing part during the operation of the turbine unit that will improve its operational reliability and cost-effectiveness. Transportation of rotor and nozzle blades, as well as the process of blading the rotors and the manufacture of diaphragms should exclude mechanical impact on their profile surfaces. The results of the work can be used in the field of power engineering, in the design and operation of steam turbines.