Optimization of the ventilation system of the air-cooled turbo generator is crucial part of the development and leads to higher power output with the same dimensions. This goes hand by hand with the implementation of FEM software, which can be used for evaluations of the concepts and prototypes before production [1–۴]. The alterations proposed in this article should cause reduction of pressure drop, better airflow distribution.

۱٫۱ Turbo Generator Cooling System

Stator of the analyze turbo generator uses multi-compartment cooling system, see Fig. 1. The principle of this cooling system is based on over-pressure and under-pressure. The end-winding area is pressurized by axial ventilator. This pressure drives the airflow through three different branches. First branch is cooling stator. From the end-winding area, the air flows through transfer ducts to so called “cold” compartment from where it goes through the stator core to the airgap [5, 6]. Second branch represents airflow through rotor. Air flows under the end cap, where it is divided to cooled end-winding and rotor winding. Rotor winding is cooled via radial ducts, which are subject of the analysis. Last, the third branch is cooling first stator packets and join both stator and rotor branch in the air gap, from where it flows through stator core to the so called “hot” compartment and to the cooler.

۱٫۲ Branch Effect

The velocity of the air which enters the rotor sub slot is very high, so the air cannot turn to the first radial ducts properly. Results is that there is non-uniform distribution of the airflow in radial ducts caused by air-vortexes, see Fig. 2. Those vortexes greatly reduce the usable cross-section. The branch effect can be calculated using empiric equation described in [7]. This equation gives us relative values of the airflow which can be multiplied by total airflow to get airflow in individual radial duct.