This paper presents the development and evaluation of scaling approaches (SAs) for the cooling flow of a large rim ventilation hydro generator. The SAs are intended for designing a model of this generator to validate the machine's pressure rise and drop characteristics.
The research begins with the establishment and selection of similarity numbers that are relevant to the hydro generator cooling flow. This foundational step provides a framework for the development of SAs, ensuring that the chosen parameters accurately reflect the critical aspects of the flow problem. The strategies aim to either match the identified similarity numbers or achieve pragmatic compromises between them. Two of the selected similarity numbers are not established in literature yet. They apply for the rotating parts of the generator. Therefore, the investigations focus on this domain. The flow domain is split into two distinct sections. The first section is the flow into the rotor hub, a large sectioned chamber around the generator shaft. The second section includes the flow in the radial rim channels, the pole gaps, and cooling channels in the stator. This flow section is referred to as the homogeneous section.
The SAs are compared to each other by evaluating CFD simulations of scaled models of both flow sections. The SAs are applied across a range of model scaling factors from 1:5 to 1:20. The evaluation is focused on two metrics. Firstly, the pressure rise and drop as crucial ventilation parameters. Secondly, the power demand is analyzed, as it is essential for it to be within a reasonable range for a model test.