|Journal||Journal of Mechanical Engineering|
|Publisher||A. Pidhornyi Institute for Mechanical Engineering Problems
National Academy of Science of Ukraine
|ISSN||2709-2984 (Print), 2709-2992 (Online)|
|Issue||Vol. 24, no. 1, 2021 (March)|
|Cited by||J. of Mech. Eng., 2021, vol. 24, no. 1, pp. 53-58|
This paper is devoted to the electrochemical and chemical aspects of the erosion-corrosion destruction of the surface layer of a wet-steam turbine rotor blade under the influence of an electrified working fluid. It considers a hypothesis about a complex mechanochemical-electrochemical mechanism of chromium and iron wash-out from the surface layer of the rotor blade metal during the destruction of the oxide film under the influence of a high-speed wet steam flow. Various versions of this process are analyzed for positive, negative, quasi-neutral, and neutral electrifications of wet steam. The possibility to hydrogenate the surfaces of rotor blades under the influence of negatively-charged droplets is shown theoretically. The damage to the blades in this case is similar to that from anodic etching. It is also shown that the process of blade surface hydrogenation takes place in any case both for electrically-charged droplets and for neutral ones. However, in the case of neutral droplets, the intensity of the process is insignificant. An experimental study was carried out for the erosion-damaged surface of a last-stage rotor blade from of the BK-50 LMP turbine that had exhausted its lifetime. The quantitative content of chromium was determined in the steel sample cut out from the blade. A decrease in chromium content in the erosion-damaged blade surface layer was found. To test the hypothesis about the similarity between the process of anodic electro-etching and the process of surface destruction under the influence of negatively-charged droplets, an electrochemical experiment was carried out on a model sample of 20X13 chromium steel. The reliefs of the damaged areas on the model sample after anodic etching and on the observable blade in the zone of exposure to negatively-charged droplets are shown to be similar. The experimental studies have confirmed the presence of a complex mechanochemical-electrochemical process of blade destruction. On the basis of the data obtained, recommendations for extending the useful life of turbine blades are formulated.
Keywords: electrification of steam, hydrogenation, erosion of blades.
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- Shubenko, A. L., Kovalskiy, A. E., Strelnikov, I. S., & Shevyakova, I. N. (1998). Otsenka vliyaniya navodorozhivaniya i korrozionnykh sred na protsess kapleudarnoy erozii elementov protochnoy chasti tsilindrov nizkogo davleniya parovykh turbin [Assessment of the effect of hydrogenation and corrosive media on the process of drop-impact erosion of elements of the flow path of low-pressure cylinders of steam turbines]. Problemy mashinostroyeniya – Journal of Mechanical Engineering, vol. 1, no. 3–4, pp. 9–15 (in Russian).
- Tarelin, A. A., Surdu, N. V., & Nechayev, A. V. (2012). Elektrofizicheskiye aspekty kapleudarnogo razrusheniya ele-mentov protochnoy chasti parovykh turbin [Electrophysical aspects of droplet impact destruction of elements of the flow path of steam turbines]. Vestnik NTU «KHPI». Seriya: Energeticheskiye i teplotekhnicheskiye protsessy i oborudovaniye – Bulletin of the NTU ″KhPI”. Series: “Power and heat engineering processes and equipment”, no. 7, pp. 88–96 (in Russian).
- Varavka, V. N., Kudryakov, O. V., Morozkin, I. S., & Zabiyaka, I. Yu. (2016). Issledovaniya v oblasti kapleudarnoy erozii energeticheskogo oborudovaniya: retrospek-tivnyy obzor i analiz tekushchego sostoyaniya [Research in the field of droplet impact erosion of power equipment: a retrospective review and analysis of the current state]. Vestnik Donskogo tekhnicheskogo universiteta – Vestnik of Don State Technical University, vol. 16, no. 1, pp. 67–76 (in Russian). https://doi.org/10.12737/18260.
- Tarelin, A. A. (2020). Teploelektrofizicheskiye protsessy v parovykh turbinakh [Teploelectrophysical processes in steam turbines]. Kharkiv: Izdatelstvo Ivanchenko I. S., 184 p. (in Russian).
- Tarelin, A. A., 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, pp. 60–67. https://doi.org/10.1134/S0040601520010073.
- Tarelin, A. A. (2014). Electrization of a wet steam flow and its influence on reliability and efficiency of turbines. Thermal Engineering, vol. 61, pp. 790–796. https://doi.org/10.1134/S004060151411010X.
Received 19 February 2021
Published 30 March 2021