Kovryga A. Creation of methods for three-dimensional modeling of the thermal state of brush-holder devices of electric generators to ensure power increase of the main units

The dissertation work is purposed to the urgent issue of the Turbogenerators reliability increasing and finding resources to ensure Turbogenerators power increasing by creating of new methods for three-dimensional calculation of the thermal state of assemblies and parts of the brush-holders device and other structural elements of Turbogenerators. The temperature distribution within the brush-holders device was calculated in order to determine the possibility of reliable operation of the Turbogenerator with a brush-holders device equipped with additional filter elements in the air cooling system. In terms of determining the temperature of the brush-holders device elements, it was found that the temperature reserves allow for safe operation of the brush-holders device with additional filters installed in the Turbogenerator without restrictions on loads and operating modes. The purpose of the dissertation is to develop methods for modeling of the thermal state of the brush-holders devices of a Turbogenerator during operation in all permissible operating modes, ensuring an increase in its power by solving a set of ventilation and heat conduction problems in a three-dimensional setting using the finite element method. The first Section of the dissertation is purposed to a general analysis of the influence of the selected cooling system of the Turbogenerator on its overall dimensions and weight and the design of the main elements. The most common cooling systems and the values of electromagnetic loads acceptable for each cooling systems which are used, are considered. The design features of the main units of the Turbogenerator are also indicated, which ensure the circulation of coolants and optimal conditions for removing temperature from active parts to ensure the requirements of regulatory and technical documentation for the operating conditions of the Turbogenerator. The second section of the dissertation is devoted to the analysis of existing methods and algorithms for calculating the thermal state of structural parts of turbogenerators. The features of the analytical calculation of the ventilation system using the analogy of hydraulic and electrical circuits, as well as the properties of the flow from the point of view of ensuring optimal heat transfer conditions, are determined. The third section considers the results of calculating the thermal state of the brush-holders device of Turbogenerators by the analytical method and in a three-dimensional formulation based on previously performed modeling of the calculation units. The distribution of cooling air flows, air pressure in the system, thermal state of air and conductive parts of the brush-contact apparatus with installed filters in the cooling system were determined. Based on the calculations, the possibility of safe operation of the apparatus in all permitted operating modes of the Turbogenerator with compliance with the conditions for permissible temperatures was confirmed. The fourth section submits the methods for testing of a Turbogenerator, including thermal tests conducted to assess the actual temperature reserves of the active parts of the Turbogenerator relative to the temperature limit values specified in the regulatory and technical documentation. The Analysis of the test results allows us to identify shortcomings in the operation of the Turbogenerator, provide recommendations for eliminating identified shortcomings in the cooling system, and identify existing reserves for a possible increase in the power of the Turbogenerator. Using the example of the results of thermal tests of an existing Turbogenerator, it is shown that disturbances in the cooling system, in particular contamination of heat exchange devices, can negatively affect the operational characteristics of the Turbogenerator, especially in the summer period of operation with maximum temperatures of cooling media, and ultimately lead to a limitation of the machine power. The result of the carried out research work was the development of effective methods for studying the thermal state of components and structural elements of Turbogenerators, in particular their brush-holders device, during operation in all permissible modes.