Computer simulation of a rotor creep

Abstract

The issue of determining the stress-strain state during creep in models of rotors of steam and gas turbines is considered. The formulation of the problem is based on the general approach of Solid Mechanics using incremental theory to describe creep strains. The Finite Element Method was used as a solution method in the implementation of professional engineering software. The influence of the centrifugal forces on the stress-strain state, which varies during 10,000 hours of creep of the rotor material, is analyzed. Two models of the rotor are considered: a simplified cylindrical and a drum-type rotor, which is described by the geometry of the body of revolution and which consists of several cylindrical parts. Due to the symmetry of the models, the calculation schemes are built on the basis of the use of a two-dimensional finite element of the body of revolution. Algorithms are applied for the preparation of input data can be recommended for use in the design practice of energy industry enterprises. The Norton law was used for creep calculations. The creep of the models in different temperature conditions with the use of various steels used in turbo-building as their material was analyzed. According to the results of the performed computer simulation of the creep of rotor models, the levels of deformation and the nature of the redistribution of stresses that occur under the same load by centrifugal forces in different temperature conditions caused by the operational processes in the turbine have been established. The stress and strain levels in the drum-type rotor were analyzed and the most loaded and deformed areas of it were determined. It is noted that according to the simulation data for the considered model of the drum-type rotor, the level of accumulated strains, is moderate and does not exceed 0.4%, which is suitable from the point of view of the analysis of operational properties.