Development and experimental implementation of a biaxial transducer to measure radial loads on a rotor shaft

Abstract

During realistic functioning conditions, rotating machinery can develop radial loads that are transmitted to the supports of the shaft (bearings) reducing their fatigue life and structural integrity. In the particular case of turbines and propellers, in-plane loads are generated due to non-uniformity of the inflow field and, beside contributing to the onset of structural issues, affect the dynamic response of airplanes and ships as well. The measure of the radial force components provide a considerable information to understand, evaluate and mitigate those effects during the life-cycle of the shaft line and for the improvement of performances. In this work, the development of a new bi-axial force transducer is described. The final design is based on a theoretical approach considering a simplified portal frame model, supported by FE analysis. This device fulfills the need to quantify radial forces acting on a rotating shaft, with low invasive design and very simple setup. The reliability of the device is demonstrated in the context of ship propulsion. It has been mounted on a scaled model of a ship, during self propelled free running maneuvering tests, providing remarkable hydrodynamic results useful to the quantification of poorly documented loads and the comprehension of the interaction between the propeller and the ship wake.