In most high-speed engines, the crankshaft systems can become one of the most dangerous excitation sources. Since the crankshaft has significant kinetic and elastic (potential) energy, and is subjected directly to the impulsive excitation forces, significant engine structure noise and vibrations can often be caused. However, all excitation forces would be transmitted from the rotating crankshaft system to the engine structure only through the crankshaft main bearings.
To investigate the excitation interaction between the crankshaft system and the engine structure, and the correlation between the crankshaft vibrations and the engine structure noise and vibrations, three phenomena were measured: (1) the crankshaft three-dimensional vibration behavior, (2) the vibration behavior of each crank journal main bearing, and (3) the engine structure noise at 1 m from the engine side. These results were obtained simultaneously, under different operating conditions, and were compared with calculated results.
Two kinds of diesel engines: a four-cylinder in-line type and a six-cylinder in-line type, and one kind of gasoline engine: a V type six-cylinder engine were used for the experiments and analyses.