Oleksandr Vasyliev

This study explores heat and mass transfer processes in the structural elements of an umbrella-type hydrogenerator, as well as the ventilation and cooling system in the active components of the hydrogenerator. A vertical synchronous air-cooled hydrogenerator with a rated capacity of 60 MW has been investigated. The task addressed relates to the cooling efficiency of generator components. Conventional analytical calculation methods do not make it possible to identify local overheating zones and pressure distribution in complex ventilation channels. Therefore, it becomes necessary to use numerical methods and algorithms to calculate and analyze the cooling efficiency of the generator’s active parts. The main result of this study is the designed structure of the guide channels (blades) of the rotor, which provides the required air flow rate of 45 m3/s. At the same time, the maximum values of the winding temperature do not exceed the permissible values for class F insulation. The CFD calculation detailed the action of the superchargers and showed the real pressure in the channels and the volume of air passing through each section of the generator. The error between the results from CFD modeling and analytical calculations is less than 3%. The results are attributed to the detailed reproduction of the geometry of the ventilation channels in the 3D model, which made it possible to determine the real aerodynamic resistance and cooling medium consumption. The proposed method uses the boundary conditions of the third kind for a comprehensive calculation of the conjugate heat and mass transfer. The proposed structure could be implemented in the design and modernization of air-cooled hydrogenerators.

The object of this study is the thermal and hydraulic characteristics of the oil coolers in a thrust bearing and guide bearing cooling system of hydrogenerators. The study addresses the task to improve the efficiency of the cooling system of the supporting elements of hydrogenerators while maintaining mass and dimension indicators. The main problems in this case are the unbalanced flow of oil within the typical cooling system and different stiffness of the thrust bearing segment supports. The main result is the design of a cooling system structure that ensures effective heat removal from the oil. According to calculations, an oil cooler for a hydrogenerator with a capacity of 56 MW provides removal of 250 kW of losses with a heat transfer margin of 26.2%, for a hydrogenerator with a capacity of 96 MW – 150 kW and 31.8%, respectively. The results are explained by the use of new antifriction materials for supporting elements (fluoroplastic-4) and a higher strength group material for the thrust bearing disk. The designed structure of the cooling system enables operation with preservation of isotropy of cooling liquids and does not have "dead" zones of these liquids flow. A feature of the proposed method for calculating oil coolers is the addition to existing criterion equations of an experimental coefficient B, which takes into account the peculiarity of the geometry of the structure in addition to the nature of the oil flow and gas-dynamic parameters. The action of three-dimensional forces, temperatures, and pressures within the base metal and cooling liquids were comprehensively taken into account. The proposed structures of the thrust bearing and guide bearing, as well as their cooling systems, could be implemented in the design and modernization of medium and high-power hydrogenerators