Research On Torsional Vibration And Silicone Oil Damper Design For Diesel Engine

The internal combustion engine has been widely used in the aerospace, automotive, shipbuilding and other machines. Mechanical vibrations of gasoline and diesel engines will be caused with the piston, connecting rod and crankshaft reciprocating. The internal combustion engine shafting will produce torsion elastic deformation because of cyclical changes in the incentive moment. Torsional vibration of the engine always exists when it works, as the source of excitation moment always exist. When crankshaft resonance, the vibration amplitude is significantly increased, even makes engine shafting fracture, brutal work and noised, so it is especially important to avoid resonance.In this paper, for an inline six-cylinder diesel engine, the concentrated mass spring-damper model was established and free vibration and forced vibration were calculated to obtain the natural frequency of the shafting, each mode shapes and the amplitude of the main harmonic, based on the lumped parameter model simplification principles. The torsional vibration measurement test bench for the engine was established. The compared results shows, the accuracy of the numerical calculation.It studied the impact of dampers structure parameters on the natural frequencies and torsional vibration peak by changing the structure parameters, based on the established model. The results show, inside diameter, outside diameter and width of the inertia ring are in a quadratic curve relationship with the natural frequency. The structure parameters are also in a linear relationship with torsional vibration amplitude of4.5harmonic frequency, are in a quadratic relationship with torsional vibration amplitude of6.0harmonic frequency.The impact of flywheel moment of inertia on the natural frequencies and torsional vibration peak was studied. The relationship of the moment of inertia of flywheel and the second-order natural frequency,4.5and6.0harmonic peak amplitude was found out. The results show, increased inertia of flywheel makes first natural frequency decreased by cubic curve, second natural frequency decreased by biquadratic curve,4.5harmonic resonance peaks increased by cubic curve,6.0harmonic resonance peak increased by biquadratic curve, which can inhibit the roll amplitude value and make rolling vibration moving to low-speed zone.60°and90°cylinder angle of torsional vibration were studied, based on the establishment of a V-shaped12-cylinder diesel engine torsional vibration calculation model. The results show, the cylinder angle does not have an impact on the natural frequencies.60°cylinder angle make angle evenly spaced, but its main harmonic amplitude of the6.0harmonic substantial increased, resulting in vibration amplitude is worse than90°cylinder angle. Reducing torsional vibration by selecting a cylinder angle should take major risk harmonic resonance times into account, not just angle uniformity.At last, the full balance and both partially balanced crankshaft structure twist amplitude values and stress were analyzed, and found that fully balanced crankshaft structure can slightly decrease the crankshaft torsional vibration and improved torsional vibration stress. The total amplitude can be reduced0.07deg.The torsional vibration stress can be reduced18MPa.