This paper describes an approach to unidirectional coupled CFD – FEM analysis developed at ABB Turbo Systems Ltd.. Results of numerical investigations concerning the vibration behavior of an axial turbocharger turbine are presented. To predict the excitation forces acting on the rotating blades, the time resolved two-dimensional coupled stator - rotor flow field of the turbine stage was calculated. The unsteady pressure, imposed on the airfoil contour, leads to circumferentially non-uniform and pulsating excitation forces acting on the rotating bladed disc.
A harmonic transformation of the excitation forces into the rotating co-ordinate system of a single blade was elaborated and the complex Fourier amplitudes were determined. The bladed rotor was modeled by a single symmetric segment with complex circumferential boundary conditions. With respect to different nodal diameter numbers free vibration analyses of the disc assembly were then effectively performed. For calculated resonance conditions, the steady state responses of the turbocharger bladed disc were computed. By using this coupled CFD - FEM analysis, the dynamic loading of the turbine blades can be determined in the design process.
