Characteristic Research On Rotor Cooling Of Large Air-cooling Turbo-generator With Multi-path Ventilation

Due to the development of the combined cycle power generation technology at present, the capacity of the air-cooling turbo-generator is promoted to be large. With the turbo-generator’s capacity increasing, the heat load increases correspondingly, thus the more efficient and reasonable ventilation cooling system is adopted to reduce the maximum temperature rise and the ventilation nonuniformity. It is very significant to forecast accurately the distribution of the air flow rate and the temperature rise inside the rotor and optimize the ventilation structure for reducing the design period of the turbo-generator and the safe operation.Some large air-cooling turbo-generator rotor with the multi-path ventilation was taken as example, and a research method with analyzing the temperature rise of the rotor region and optimizing the ventilation structure according to the air flow rate distribution characteristic of the rotor ducts was presented. Firstly, the 3D calculation model of the multi-path ventilation flow field among the half axial rotor was established. Based on Computational Fluid Dynamics (CFD) principle, the relative governing equations were solved by Finite Volume Method; the air flow rate distribution characteristic of the rotor ducts was obtained; the high temperature region of rotor was forecasted, and the effect of inlet pressure on the air flow rate distribution was analyzed. Secondly, the 3D flow and heat transfer calculation models concluding the rotor end region and the winding rotor body segment were calculated based on the research on the air flow rate distribution of the half axial rotor, and the temperature rise of the rotor end region and the windings axial temperature distribution among the rotor body segment was obtained. In the end, on basis of the research results mentioned above, the ventilation structures were changed in order to decrease the local high temperature of the rotor and improve ventilate uniformly. The effect of the structure and arrangement of the rotor end insulation blocks, the length of axial and sub slot ventilation, the ventilation structure of the cushion strip beneath wedge, the center section height of the axial sub slot and the position of the end ventilation inlets on the air flow rate distribution was analyzed, and the more ideal ventilation structure of rotor was presented finally, and the physical field characteristic was analyzed. The research method and conclusions mentioned above will provide theoretical guidance to optimization design of the rotor ventilation structure and the safe operation of large air-cooling turbo-generator.