Thermal analysis of the rotor of large air-cooled turbo generators

The present paper deals with an investigation of thermal characteristics of the rotor of large air-cooled turbo-generators. To model the complex geometry of the rotor cooling system, thermal network method is applied by considering uniform nodes along the rotor body and rotor conductors. Thermal resistances and different losses are considered and consequently by employing iterative solution, temperature distribution at different parts and convection coefficient in the airgap and radial subslot are evaluated. Results showed that convection coefficient increases along the rotor axis in radial subslots. In addition, about 8 degrees of air temperature rise is reported at the end of the subslot. Furthermore, the air is subjected to approximately 25 degrees of temperature rise as passes from subslot to airgap through radial subslots. In general, the amount of flowrate and angle of inclination of radial subslot have a dominant role on the cooling effect of the air. This necessitates the need for further optimizing the flow geometry of radial subslots. Results are in good agreement with available official data.