Validating a CFD Simulation Approach by Ventilation Measurements for an Air-Cooled Salient Pole Model Generator

Pressure and flowrate measurements were conducted for an air-cooled salient pole hydro model generator in order to validate a computational fluid dynamics (CFD) simulation approach. The ventilation system of the model generator was driven by adjustable external fans, which allows detailed pressure measurements for a range of operating conditions. The CFD model to be validated consists of full generator geometry which is modelled in high geometrical detail. The steady-state multiple reference frame approach was chosen for the simulations, and the influence of different rotor-stator interfaces and turbulence models was investigated. The comparison of measurement and simulations includes the static pressure along the flow path through the machine, the performance map of the external fans, and an analytical approach to describe the dimensionless machine parameters of the model generator. Good overall agreement was found between measurement and CFD, which justifies the application of the presented simulation approach in the design of ventilation and cooling systems for hydro power generators. Qualitatively the CFD simulations reproduced all measured flow effects. Also quantitatively a good prediction of measured values was identified for a broad range of operating conditions. However, it was found that the simulation accuracy does not only depend on the numerical models in use but also on the specific operating conditions and their affiliated airflow characteristics.