Vibrational Stresses in the Last-Stage Blades of a Powerful Steam Turbine Under Kinematic Excitation Of Oscillations. Part 1. Investigation of Cyclic-Symmetric Systems

IF 0.7 4区 材料科学 Q4 MATERIALS SCIENCE, CHARACTERIZATION & TESTING
M. G. Shulzhenko, A. S. Olkhovskyi, O. L. Derkach
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Abstract

The influence of kinematic excitation of rotor vibrations of a powerful steam turbine without and with disturbance of blade vibration frequencies on the extension of their trouble-free operation is evaluated. The results of determining the maximum equivalent stresses of the blades under the condition of power and kinematic excitation of stationary oscillations are presented. A system with cyclic symmetry is considered. The three-dimensional finite element models of the disk–blade system and the corresponding mathematical support for calculating stationary harmonic oscillations are used. Computational studies to determine the maximum equivalent stresses of the blades were carried out under the condition of simultaneous action of power excitation of oscillations from the steam flow with a frequency of the forcing force of 2100 Hz (with the number of guide blades of 42) and kinematic excitation due to rotor vibration on sliding bearings with a frequency of 50 Hz. The load from the steam flow on each blade was set to be linearly variable from zero at the root to 1 kPa and 5 kPa at the apex, as well as a uniformly distributed 2.5 kPa along the blade, acting normally at points on their working surface. The kinematic excitation was set as an ellipse describing the motion of the disk center in its plane. It is assumed that the physical and mechanical properties of the blade material are preserved after their repair and surface treatment. The change in the maximum equivalent stresses for different variants of blade loading in a cyclic-symmetric disk–blade system under kinematic excitation of oscillations is evaluated. The obtained results are compared with the data for the system with all damaged blades after restorative repair in their lower part under the condition of kinematic excitation of vibrations and without repair. These results confirm the practicality of assessing the stress state of the last stage blades of a powerful steam turbine, considering the disk–blade system’s kinematic excitation when determining their operation’s reliability.

Abstract Image

大功率蒸汽轮机末级叶片在振荡运动激励下的振动应力。第 1 部分。循环对称系统的研究
对无叶片振动频率干扰和有叶片振动频率干扰的大功率蒸汽轮机转子振动运动学激励对延长其无故障运行时间的影响进行了评估。结果显示了在功率和静态振动运动学激励条件下叶片的最大等效应力。考虑的是一个具有周期对称性的系统。使用了圆盘-叶片系统的三维有限元模型和计算静态谐波振荡的相应数学支持。在蒸汽流的动力激励振荡频率为 2100 Hz(导向叶片数量为 42 片)和滑动轴承转子振动的运动激励频率为 50 Hz 的条件下,进行了计算研究,以确定叶片的最大等效应力。每个叶片上的蒸汽流载荷设定为线性变化,从根部的零到顶点的 1 kPa 和 5 kPa,以及沿叶片均匀分布的 2.5 kPa,正常作用于叶片工作面上的各点。运动激励设置为一个椭圆,描述圆盘中心在其平面上的运动。假定叶片材料的物理和机械特性在修复和表面处理后保持不变。在运动学振荡激励下,对循环对称圆盘-叶片系统中不同叶片加载变量的最大等效应力变化进行了评估。获得的结果与所有受损叶片下部经过修复后的系统数据进行了比较。这些结果证实,在评估大功率蒸汽轮机末级叶片的应力状态时,考虑到盘形叶片系统的运动激励,在确定其运行可靠性时是切实可行的。
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来源期刊
Strength of Materials
Strength of Materials MATERIALS SCIENCE, CHARACTERIZATION & TESTING-
CiteScore
1.20
自引率
14.30%
发文量
89
审稿时长
6-12 weeks
期刊介绍: Strength of Materials focuses on the strength of materials and structural components subjected to different types of force and thermal loadings, the limiting strength criteria of structures, and the theory of strength of structures. Consideration is given to actual operating conditions, problems of crack resistance and theories of failure, the theory of oscillations of real mechanical systems, and calculations of the stress-strain state of structural components.
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