Simulation of the Erosion-Corrosion Destruction Process of Steam Turbine Low-Pressure Cylinder Blades

Authors

Oleksandr L. Shubenko, Anatolii Pidhornyi Institute of Mechanical Engineering Problems of NAS of Ukraine (2/10, Pozharskyi str., Kharkiv, 61046, Ukraine), shuben@ipmach.kharkov.ua, ORCID: 0000-0001-9014-1357

Anatolii O. Tarelin, Anatolii Pidhornyi Institute of Mechanical Engineering Problems of NAS of Ukraine (2/10, Pozharskyi str., Kharkiv, 61046, Ukraine), tarelin@ipmach.kharkov.ua, ORCID: 0000-0001-7160-5726

Abstract

This paper is devoted to the important problem of creating a method for predicting the intensity of erosion-corrosion destruction of the working blades material of low-pressure stages of powerful steam turbines, considering the complex physical processes that accompany the emergence, transformation of erosion-hazardous droplets and their interaction with elements of the flow path. The features of the construction of some existing erosion models are considered. The model that is developed at the Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine and based on a deterministic-statistical approach to its creation is analyzed in detail. The calculations performed during the research showed a satisfactory coincidence with the results of experimental tests by various authors, obtained on droplet impact stands, which contributed to the successful use of the model in creating a comprehensive method of predicting the wear of working blades. To do this, it was supplemented by the method of determining the parameters of the erosive environment based on the droplet movement equation, taking into account the size distribution law. Along with that, it is shown that the considered model, although it allows to carry out fairly accurate prediction of the development of erosive wear at the modern level, has difficulties in its construction due to the need to identify it from the data of full-scale experiments, the number of which is limited. It has been established that one of the important reasons for the discrepancies that arise is the failure to include of the electrophysical component of the processes occurring in a two-phase flow. In this regard, the results of comprehensive studies of steam electrization and its influence on the working processes of wet steam turbines are considered. It is shown that the change in the properties of the working medium as a functional erosive medium as a result of electrification causes a significant increase (relative to neutral wet steam) of electrochemical processes. At the same time, the kinetics of the damage accumulation to the metal surface layer changes due to the joint occurrence of several negative processes: droplet impact influence; electrochemical processes caused by mechanical and structural and chemical heterogeneity of the surface; hydrogen absorption; changes in mechanical properties under the electric field influence. It was noted that the contribution of hydrogen absorption to changes in mechanical properties is the greatest. According to a preliminary assessment, the complex negative droplet impact and electrophysical influence on the metal surface reduces the incubation period and intensifies the erosion-corrosion process by approximately 2 times

Keywords: steam turbine, wet steam, rotor blades, droplet impact destruction, mathematical modeling, electrophysical effects, electrocorrosive processes

Full text: Download in PDF

References

1. Shubenko, A. L. & Kovalskiy, A. E. (2012). Kapleudarnaya eroziya lopatochnykh apparatov parovykh turbin. Prognozirovaniye i metody zashchity [Drop impact erosion of steam turbine blades. Forecasting and protection methods]. Vestnik Natsionalnogo tekhnicheskogo universiteta «KhPI» – NTU “KhPI” Bulletin: Power and heat engineering processes and equipment, no. 7, pp. 76–87 (in Russian).
2. Krzyzanowski, J. A. (1988). On predicting steam turbine blading erosion and turbine efficiency deterioration. ASME Proceedings Series. Turbo Expo: Power for Land, Sea, and Air. Vol. 1: Turbomachinery, Paper No. 88-GT-224, V001T01A080, 9 p. https://doi.org/10.1115/88-GT-224.
3. Khodykina, G. I. & Saprunov, G. I. (1984). Metodika chislennogo modelirovaniya erozionnogo iznosa detaley energoustanovok [Numerical modeling technique for erosive wear of power plant parts]. Proyektirovaniye, konstruirovaniye i prochnost elementov konstruktsiy reaktivnykh dvigateley – Design, construction and strength of structural elements of jet engines: Collection of scientific works of the Sergo Ordzhonikidze Moscow Aviation Institute, pp. 52–58 (in Russian).
4. Poddubenko, V. V. & Yablonik, R. M. (1976). Vliyaniye struktury potoka kapel na eroziyu turbinnykh lopatok [Effect of droplet flow structure on turbine blade erosion]. Izvestiya vuzov. Energetika – Energetika. Proceedings of Higher Education Institutions, no. 4, pp. 88–93 (in Russian).
5. Ruml, Z. & Liska, A. (1987). A model for the erosion of steam turbine blade materials. Proceedings of 7th Scientific Conferences on Erosion by Liquid and Solid Impact, England, Cambridge, University of Cambridge, September 13–15, 1987. U.K., England, Cambridge: University of Cambridge Publ., Paper 15, pp. 1–8.
6. Springer, G. S. (1976). Erosion by liquid impact. USA, Washington: Scripta Publishing Co.
7. Tishchenko, V. A., Alekseev, R. A., & Gavrilov, I. Y. (2018). A model of the motion of erosion-hazardous droplets in steam turbines’ interblade channels. Thermal Engineering, vol. 65, iss. 12, pp. 885–892. https://doi.org/10.1134/S0040601518120108.
8. Shubenko, A. L. & Kovalskiy, A. E. (1989). Kineticheskaya model kapleudarnoy erozii rabochikh lopatochnykh apparatov parovykh turbin [Kinetic model of drop impact erosion of working blades of steam turbines]. Izvestiya AN SSSR. Energetika i transport – Proceedings of the Academy of Sciences of the USSR. Energy and transport, no. 5, pp. 94–101 (in Russian).
9. Krzyzanowsky, J. A, Kovalsky, A. E., & Shubenko, A. L. (1994). Some aspects of erosion predicting of steam turbine blading. Journal of Engineering for Gas Turbines and Power, vol. 116, iss. 2, pp. 442–451. https://doi.org/10.1115/1.2906841.
10. Tarelin, A. A. (2020). Teploelektrofizicheskiye protsessy v parovykh turbinakh [Thermal electrophysical processes in steam turbines]. Kharkiv: FLP Ivanchenko I. S., 184 p. (in Russian).
11. Tarelin, A. O., Surdu, N. V., & Nechaev, A. V. (2020). The influence of wet-steam flow electrization on the surface strength of turbine blade materials. Thermal Engineering, vol. 67, iss. 1, pp. 60–67. https://doi.org/10.1134/S0040601520010073.
12. Orlova, D. V., Filipiev, R. A., & Danilov, V. I. (2012). O vozmozhnykh prichinakh vliyaniya elektricheskogo potentsiala na soprotivleniye metallov mikroindentirovaniyu [About possible causes of electric potential inuence on the resistance of metals to microin-dentation]. Izvestiya vuzov. Chernaya metallurgiya – Izvestiya. Ferrous Metallurgy, vol. 55, no. 10, pp. 66–67 (in Russian). https://doi.org/10.17073/0368-0797-2012-10-66-67.
13. Orlova, D. V., Danilov, V. I., Zuyev, L. B., Kolesnik, A. S., Dulbeyeva, O. N. (2012). O vliyanii elektrostaticheskogo polya na mikrotverdost’ monokristallov tsinka [Effect of electrostatic field on microhardness of zinc single crystals]. Obrabotka metallov – Metal Working and Material Science, no. 4, pp. 98–102 (in Russian).
14. Tarelin, A. A. (2017). Postfact phenomena of the wet-steam flow electrization in turbines. Thermal Engineering, vol. 64, iss. 11, pp. 810–816. https://doi.org/10.1134/S004060151711009X.
15. Tarelin, A. O., Shvetsov, V. L., Mykhailenko, V. H., Nechaiev, A. V., & Khinievich, O. Ye. (2021). Electrochemical and chemical mechanisms of the erosion-corrosion process of wet-steam turbine rotor blades destruction under the influence of electrified moisture. Journal of Mechanical Engineering – Problemy Mashynobuduvannia, vol. 24, no. 1, pp. 53–58. https://doi.org/10.15407/pmach2021.01.053.

Received 12 December 2022

Published 30 March 2023