Palkov S. Improvement of inner shells of К-500-240 series steam turbines by increasing their heat-resistant characteristics

The dissertation is devoted to the study of the stress-strain state (SSS) of the inner shell of К-500-240-2 turbine. There has been developed the methodology of calculating the thermal stress state of the inner shell of the steam turbine in three-dimensional elastic-plastic setting taking into account the creep and thermo contact interaction of the structural elements, which allowed in comparison with the existing approaches to more accurately take into account the influence of the various factors on SSS of the inner shell and to obtain the distribution of the contact pressure on the interacting surfaces. To verify the improved calculation method, an experimental study of SSS and contact interaction of the structural elements has been performed. A new approach to the experimental determination of the contact pressure is proposed, which uses the indirect measurements of the deflection of the seal depending on the applied force in the fastening, which allows obtaining the local numerical characteristics of the contact interaction. There have been estimated the kinetics and the general level of creep deformation and stress relaxation at the nominal mode of operation of the turbine unit in the range from commissioning up to operating of 300 thousands of hours as well as there has been established the list of the dangerous zones of the design of the case in which the emergence and development of the damages is possible. Based on the obtained results, recommendations for the improvement of the internal body of HPC of K-540-23.5 turbine have been developed, which allow to get rid of a number of prevention of the negative phenomena caused by the high stresses in the structure.