Analysis of nodal diameter zero blade vibrations of a radial turbine

This paper presents results of strain gauge measurements, which have been carried outon a full scale turbo charger test rig. Rotational speed of the turbo charger was rampedup and down through four preliminary anticipated rotor blade resonances, with a knowncombination of main order of excitation and corresponding nodal diameter. An analysisof the transient data is presented. An investigation of spectra with high frequency resolutions,centered on individual blade resonance points in time, is presented. In contrast toformer research, all blades resonate at the same point in time and thus at the same resonancefrequency, if the excitation corresponds to a nodal diameter of zero. Strain datafrom the shaft is used to support findings, which, in other publications, often solely relyon strain data from individual blades.