a c-based n Method and System for Determining Critical Speed ​​of Steam Turbine Rotor by Group Theory

Abstract

The invention discloses a turbine rotor critical rotating speed determination method and system based on a CN group theory; the method comprises the following steps: building a turbine rotor 3D geometry model, and selecting certain portion of the 3D geometry model as a basic sector; building a basic sector local coordinate system, dispersing the basic sector, and calculating dynamic characteristic parameters of each dispersed unit; building a turbine rotor kinetic model according to the CN group theory and the basic sector dynamic characteristic parameters; using the kinetic model to calculate and obtain each stage fixed frequencies of the turbine rotor, thus determining the critical rotating speed. The turbine rotor critical rotating speed determination method and system is clear in process, high in calculation efficiency, accurate in result, and suitable for fast finding the turbine rotor critical rotating speed in engineer design, tests and operations.

Description

technical field [0001] The invention relates to a C-based N A method and system for determining the critical speed of a steam turbine rotor based on group theory. Background technique [0002] There are two existing methods for obtaining the critical speed of the steam turbine rotor: the calculation method and the actual measurement method. Although the actual measurement method can accurately measure the critical speed of the rotor, it has great limitations. For example, when the critical speed is greater than the operating speed, the critical speed of the rotor cannot be obtained by actual measurement. Calculation methods mostly use over-simplified models of the actual steam turbine rotor geometry, support stiffness, etc., resulting in a certain error between the calculated and measured values; while using the real model of the rotor has a huge calculation scale and low solution efficiency. [0003] The reports on the calculation method of the critical speed of the steam...

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Problems solved by technology

For example, "The Influence of Blade Row Dynamics Lateral and Torsional Shaft Vibrations in Steam Turbines" was published at the 9th International Conference on Rotordynamics in 2015, which simplifies the blades in the steam turbine rotor to the mass units at the top of the blades, and the gap between adjacent blades The connection at the blade root and the connection at the blade root are replaced by equivalent springs. This simplified model can efficiently calculate the interaction law between blade vibration and shaft vibration, but it cannot reflect the distribution of blade mass in the blade length and width directions, resulting in There is a large error between the calculated value and the real value of the critical speed of the steam turbine rotor

"Study on Coupled Vibration of Steam Turbine Long Blade Bending and Shafting Torsion" was published in the 6th issue of "Journal of Power Engineering" in 2014. It establishes a three-dimensional model based on the actual structural parameters of the steam turbine rotor, and uses the full-ring model for calculation, which can accurately obtain the The critical speed of each stage of the rotor, but the solution scale is too large and the efficiency is low

[0004] In addition, the 2014 ASME Turbine Technology Summit released "Last Stage Blade Coupled ShaftTorsional Vibration Analysis of 1000MW Steam Turbine Generator Set by aReduced 3D Finite Element Method", which establishes a three-dimensional model based on the actual structural parameters of the steam turbine rotor, and uses substructure The modal synthesis method extracts the important low-order vibration shapes of the rotor, which not only ensures the accuracy of the calculation but also improves the calculation efficiency. However, this method has high requirements on the theoretical basis and programming ability of technicians, and has certain operational difficulties.

[0005] In summary, the existing methods for obtaining the critical speed of steam turbine rotors have problems such as limited application of the actual measurement method, certain errors between the calculation method and the real value, or high difficulty of calculation, which makes it difficult for the calculation method to be used for steam turbine rotors with multi-stage blades.

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