Study of a high rotational speed shrouded centrifugal fan: aerodynamics and effects of a shroud-associated cavity on the performance

A centrifugal fan with a high rotational velocity and compact dimension is studied numerically and experimentally in this paper. The fan consists of a shrouded impeller rotating at 34 000 r/min with a small cavity between the impeller and outer casing. The overall performance and the major flow features have been numerically and experimentally investigated. For the numerical simulation, two computational models with/without the cavity were tested. The modelling of a very-small-size cavity is generally time-consuming, compared with the outer domain. However, it has been shown that its effect can be taken into account with a simple method discussed in this study. A simple volumetric loss model coupled to a numerical modelling of the fan without the cavity gives a very interesting approximation of the global performance of the fan. In the present work, the overall performance and the major flow features of each component inside the fan were numerically investigated. The numerical results at different locations were compared with experimental ones. It is shown that the results obtained by the simplified method and the full numerical simulation both predict the global performance obtained experimentally. Furthermore, in terms of the flow restriction obtained for the centrifugal fan, new empirical coefficients accounting for the effects of the cavity were set.