Some Aspects of Erosion Prediction of Steam Turbine Blading

This paper deals with an issue of paramount importance for the turbine manufacturer today: the mathematical modeling of erosive wear at the inlet rotor blade edges by streams of coarsely dispersed liquid droplets. In the methodology of blade material wear an important element is the erosion model or material response Y = Y (τ) to the droplet impact intensity. On the background of this erosion model development the approaches of Szprengiel and Weigle (1983), Szprengiel (1985), and Shubenko and Kovalsky (1987) are presented and applied for erosion calculation of some real turbine blade profiles. There are, however, several factors that affect the erosion prediction quality as well as the field experimental data. Hence a procedure for verifying the methodology of the erosion prediction by experimental data is necessary. Krzyzanowski (1987, 1988, 1991) used for that purpose the calculated and measured erodet area of various turbine blade profiles. Here the comparison of the calculated and measured erosion width η_B ≡ z has been used to verify the prediction methodology of erosion. The use of η_B instead of erosion area looked promising since acquiring η_B experimental values seemed easier than any other geometric characteristics of the blade erosion wear. It has been shown, however, that the prediction of η_B underestimates the blade erosion wear for both material response models. To cope with the scatter of experimental data, statistics have been used. Reasons for this scatter and differences between the calculated (η_Bcalc) and measured (η_Bm) values of the erosion field width have been suggested. The list of factors that affect the erosion prediction quality may be looked upon as a list of promising topics of further research on the subject.