APPLICATION OF BREAKDOWN MECHANICS FOR PREDICTING THE RESOURCE OF AXIAL RADIAL HYDROTURBINS

E V Georgievskaia

doi:10.30724/1998-9903-2018-20-9-10-71-78

Abstract

To plan for timely reconstruction, modernization, repairs or replacement of equipment it is important to reliably predict the instant of its transition to the limiting state that determines the lifetime. Currently, there are no regulatory methods for assessing the lifetime of hydraulic turbines at the operation stage. The approach presented in this paper uses the fracture mechanics methods to build a long-term individual forecast of the dangerous development defects in the main elements of hydraulic turbines taking into account design, technological and operational features. The forecast is based on three-dimensional mathematical models that describe the change in the technical condition of the equipment during time under actual operation. The ANSYS software is used for calculations. Models take into account the size and position of detected or possible defects. Crack growth is determined by the combination of low- and high-frequency loads. The critical length of the crack corresponds to the instant of change of the crack development mechanism, when the failure risk increases sharply. Proposed approach can significantly reduce the possibility of unplanned or emergency shutdown of the hydraulic unit due to its destruction during the overhaul period.

Highlights

For many years in hydropower dams, especially high dams, have been considered as a main potential source of danger
A more precise expression are given by different refined equations, for example, (2) – Yarema formula [11], which describes all three stages of crack growth (Fig. 5), but requires knowledge of more constants of the material: ж) L123 д) L91
Practical difficulty In practice, the detection of cracks in the elements of hydraulic turbines is not such a simple task [13,14,15]. This is due to the following main factors: large dimensions of hydraulic units and their components; actual sensitivity of non-destructive testing methods (NDT); limited accessibility of control sites; rare scheduled repairs; location of possible defects; quality of checked surfaces and the possibility of their careful preparation for control

Summary

Introduction

For many years in hydropower dams, especially high dams, have been considered as a main potential source of danger. Hydraulic units that differed by high maneuverability were forced to significantly change the operating modes. The number of starts and shutdowns of equipment and the time of its operation at non-optimal capacities increased significantly, large dynamic loads acted on the unit, causing high stresses in its elements.

Results

Conclusion