Zdravko Schauperl

Application of ESPI-method for strain analysis in thin wall cylinders

The Centre for Industrial and Engineering Optics, DIT, Ireland, have recently developed and applied new optical techniques for the measurement of mechanical strain, one of which was based on electronic speckle pattern interferometry (ESPI). The accuracy of this optical technique when used on flat surfaces is well established. In this research the technique is tested on curved surfaces, and results are compared with the theoretical hoop strain as predicted by the bi-axial strain equation modified for the thin cylinder, and by those obtained by electrical resistance strain gauge (ERSG) undoubtedly the principal method of measuring mechanical strain. For testing procedures, a special unit was designed and produced for holding and loading the thin cylinder. Also the basic equation for hoop strain by ESPI for flat surfaces was modified for applications on curved surfaces. Thin cylinder hoop strain obtained by ESPI and calculated by a modified equation show remarkably good correlation to the predicted theoretical value as well as to the results obtained by ERSG. Since the ESPI theory was originally developed for use on flat surfaces, there are reasonable grounds for further investigating this relationship especially where curved surfaces are involved.

Analysis of Deposited Salts in the Through-Flow Area of a 210 MW Steam Turbine

Abstract During the exploitation of a steam turbine, mainly because of non-adequate purity of fresh steam, salts can be deposited on the components in the through-flow area. Deposited salts decrease the reliability and efficiency of the steam turbine, while thicker layers, i. e. higher quantities of deposited salts, could cause serious damage to the turbine. This paper gives a description of deposited salt layers in the through-flow area of a 210 MW steam turbine and presents the results of research and analysis. In order to determine the cause of salt deposition on turbine surfaces, a chemical analysis of deposited layers was carried out. This paper proposes measures to reduce the salt deposition as well as methods for the removal of deposited layers in the through-flow area of a steam turbine.

Erosion Process of 66 MW Steam Turbine Rotor Blades

Abstract Apart from erosion of leading edges, erosion of the rotor blades trailing edges often occurs in condensing steam turbines, due to the impact of wet steam water droplets. Considerable erosion of the rotor blades trailing edges may be more dangerous for a reliable turbine operation than the leading edges erosion. During several years of research many results concerning erosion damage to the trailing edges of 66 MW condensing reduction steam turbine final stage rotor blades at the Thermo-electric power plant – heating plant (TE-TO) Zagreb have been gathered and are presented in this paper. Correlation between the erosion process behavior of the last stage turbine rotor blades trailing edges and the number of operating hours has been established.