Experimental study of the latest design of the powerful air-cooled turbogenerator stator

Sigre 2008Electrosila RussiaThe main circumstance limiting the turbogenerator capacity having indirect gas cooling is the heating of the stator winding. The natural aspiration to reduce this stator winding heating is connected with the intensification of the convective heat exchange in the stator tooth zone. This purpose is achieved in the investigated design owing to bypass of cooling gas between adjacent radial ducts through slit axial ducts in the stator teeth. In that way, extension of the total cooling surface in the stator tooth zone, radical reduction of considerable path portion of the heat flow from the winding to the axial cooling ducts and increase of heat-transfer coefficients in radial ducts are achieved. A number of variants of arranging the cooling air flow in the radial ducts was rendered using vent spacers, and for each variant some experiments over a wide range of air flows and heat loads were done. Detailed measurements of the local air velocities, air flow temperature and duct surfaces temperature were made. Visualization of the air flows and the temperature distribution on the radial duct surfaces was used as an additional tool for studying the heat transfer process. Finally the integral characteristics of heat transfer in the radial and axial ducts were obtained and some measures on design optimization were taken.