Unsteady Flow Calculation in a Cross-Flow Fan Using a Finite Element Method

In order to predict rotor-stator interactions in hydraulic turbomachinery, a new multidomain method was implemented in a turbulent flow finite element code. The formulation is based on the mortar element method, extended to sliding meshes. It allows the coupling between several domains using nonconforming discretization on the interface. This method was used to study the unsteady flow in a cross-flow fan. Such fans are widely used in air-conditioning devices. They consist of a cylindrical rotor with forward curved blades, rotating in a housing. The air passes the blades twice at the inlet and the outlet of the impeller while a large vortex is noticeable inside the impeller which is located in the blading near the stabilizer. The numerical results are compared to Laser Doppler Velocity measurements and to steady calculations obtained by replacing the blades by a rotating force field. The unsteady calculation shows the formation of the vortex structure at the start-up and the periodic established flow after a few revolutions of the impeller.