INVESTIGATION OF THE FLUID FLOW IN A ROTOR-STATOR CAVITY WITH INWARD THROUGH-FLOW

The present paper covers fluid flow in rotor-stator cavities with inward through-flow. First, a general introduction into the physics of the cavity boundary layer flow is given. The structure of the flow is very complex and depends on different dimensionless parameters. For practical applications, simple and robust calculation procedures are crucial for design purposes. Two basic modelling approaches are compared (3 layer model of Kurokawa [14] and "one layer" approach of Mohring [17]) with experimental data from the literature. The flow models are classified in context of the simplified equations of motion by emphasizing the main assumptions and simplifications in their derivation. Further on, for the one layer model, the use of the logarithmic law for the velocity distribution close to the wall is proposed instead of the classic 1/7 power law. The modified flow model is validated against experimental data for different parameter combinations, yielding better agreement for moderate inlet rotation. Finally numerical simulations have been performed in order to investigate the discrepancies between measured and calculated core rotation distributions for strong inlet swirl. It is supposed that the assumption of radial equilibrium in the core region is not necessarily appropriate for evaluation of the core rotation. Further on, it is clarified in which situations the tangential velocity component of the absolute velocity at the impeller outlet can be used as a boundary condition for the flow model.