| In this dissertation, the three-dimensional flow field in a centrifugal squirrel-cage blower is numerically investigated. The fan rotor is enclosed by a spiral-shaped volute that is azimuthally asymmetric. Due to the complex geometry, a detailed 3D transient solution with rotating blades would require a prohibitively high number of grid points and long CPU runtimes that are impractical, especially in an industry setting without access to supercomputers.; Therefore, a novel approach has been taken in the present work: The unsteady incompressible laminar Navier-Stokes equations which govern the flow field are averaged over time, resulting in equations for the mean flow. Due to the averaging process, new force per unit volume terms arise in the equations, representing the action of the blades on the flow.; To model the additional terms, the periodic 2D flow field between two single blades is calculated for a range of flow parameters (flowrate per unit span, preswirl), and forces are extracted from these solutions. These forces approximate the forces in the 3D machine at a location with the same flow parameters.; Then, the mean flow field in the 3D machine is calculated, with blades replaced by the previously calculated blade forces. Since no physical rotating blades are present in the 3D model, there is no need to grid the blade region in great detail. Furthermore, only a steady-state solution is required, as opposed to a transient simulation for a rotating grid approach. Both simplifications lead to substantially reduced CPU time and significantly lower computational cost.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat. |
