Theoretical and experimental investigation on vibration phenomena of the interaction between the alternator and the Ferrari V8 engine

摘要

The purpose of this study was to investigate the dynamic behavior and response of a critical component (alternator) of a high performance automotive engine, in order to predict and avoid failure during its operation. Both a theoretical (analytical) modal analysis and a comparison with operational data were performed and integrated each other in order to achieve the above objectives, and to determine the modal parameters of the component, namely: natural (or resonant) frequencies, damping factors and modal shapes. These modal parameters provide a theoretical description of the structure's dynamic behavior. The comparison with operational data has come to an end with the definition of a test profile, in order to make the qualification of the vibrating component, according to the test tailoring specifications: 8 hours test on a shaker. A measurement campaign was performed on the component, by setting up a complete measuring system, to determine the FRFs of the alternator and to perform the modal analysis. The measuring system was made up of some full measuring chains, from transducers (namely accelerometers, which were mounted on the structural component to be investigated) to data acquisition and processing equipment (the LMS Scadas Mobile and a laptop PC). The forcing function was generated by an instrumented impact hammer. The analysis of the signals relies on Fourier Analysis. The resulting transfer function showed the most critical resonances whose characteristics (the above mentioned ones) were estimated from the measurements and then compared with the theoretical ones. The analysis on the stand-alone component was then improved with the creation of a multibody simulation model of the whole driveline (namely, a driving belt) that, from the crankshaft, drives the alternator and other automotive equipments (compressor and power steering pump). This permitted to achieve a better knowledge of dynamic and vibration phenomena associated with the interaction between the alternator and the engine.