PSI - Issue 59

M.G. Shulzhenko et al. / Procedia Structural Integrity 59 (2024) 337–343 M.G. Shulzhenko et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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The presented results characterize the distortion of the axisymmetric form of vibrations in the vicinity of the damaged blade. Three lines of minimum (nodal) displacements can be distinguished from the above examination for the damaged blade, almost twice as many such lines are observed for the other blades. At the same time, there is an unequal increase in the number of nodal lines on individual groups of blades. The above allows us to visually assess the impact of a damaged blade on the formation of the vibro-stressed state of the disk-blade system. 4. Conclusions Based on the calculation results, it can be observed that at the vibration excitation frequency of 2100 Hz, the maximum stresses during kinematic excitation are observed in the lower third of the blades where the maximum stresses already occur without kinematic excitation. The increase in maximum equivalent stresses in these blades due to kinematic excitation ranges from 10% to 35%. The largest increase is observed in the seventeenth blade, which is opposite to the direction of rotation of the rotor. While this increase may not be as significant as in some other blades, it can still be crucial in evaluating the strength of the blade, particularly around the thirty-ninth blade where the stresses are the highest. These findings confirm the importance of considering kinematic excitation in assessing the stress state of the blades in the last stage of a high-power steam turbine. It highlights the significance of broken cyclic symmetry in the disk-blade system when determining the reliability of blade operation. Further research will focus on determining the vibration stresses in the blades caused by kinematic excitation at rotor rotation frequencies in the range of 50 Hz. Acknowledgements The paper has been prepared as part of the project "Development of methods for vibration diagnostics of local inhomogeneities of non-conservative mechanical systems of a complex structure based on the characteristics of their vibrations" (Agreement No. 1.3.4.2207). References Torop, V.M., Makhnenko, O.V., Saprykin, G.Yu., and Gopkalo, E.E., 2018. Results of studies on the causes of cracking in titanium alloy blades of K-1000-60/3000 steam turbines. Tekhn. Diagn. Nerazr. Kontr. 2, 3 – 15. Shulzhenko, N.G., and Olkhovskyi, A.S., 2021. Vibrational stresses of damage steam turbine blades after renovation repair. J. Mech. Eng. 24, 42 – 52. Shulzhenko, M.G., Zinkovskyi, A.P., and Olkhovskyi, A.S., 2022. Vibration stress of the last-stage blades of a steam turbine after repair of a single blade. Strength Mater 54, 565 – 575. Rzadkowski, R., Troka, P., Manerowski, J, et. al., 2022. Nonsynchronous rotor blade vibrations in last stage of 380 MW LP steam turbine at various condenser pressures. Appl. Sci. 12, 4884. Siewert, C., and Stüer , H., 2017. Transient forced response analysis of mistuned steam turbine blades during startup and coastdown. J. Eng. Gas Turbines Power 139(1), 012501. Kaneko, Y., Watanabe, T., and Furukawa, T., 2022. Study on the vibration characteristics of bladed disks with damping mistuning. GT2022 79644, V08BT27A002. Kicinski J. Rotor dynamics, 2006. Poland, Gdansk: IMP PAN.