Influence of Rotor Design on the Generation of Windage Power Loss in Salient Pole Generators

In order to determine the impact of various rotor structural elements on generation of windage losses, a computational fluid dynamics study on one salient pole generator has been performed. A fully predictive approach was employed in order to simulate airflow through the machine for five rotor configurations. The simulation results are compared with measurements and an agreement of -1.2% for losses and -2.4% for the flow rate is achieved. The analysis shows that between 84% and 90% of the overall windage losses can be attributed to centrifugal fans and poles. Regardless of the rotor configuration, the contribution of poles to the overall windage losses is always significant and ranges from 29% to 80%. A connection between the velocity field behind the fans and the losses generated by the poles is determined. An additional analysis was performed to study the causes of the vortex appearance at the fan impeller inlet.